Re: [PSES] MOV failure detection
Doug I think your assumptions are correct. It's pretty much physical inspection. Specifically MOVs may split open and smoke may escape. Gas protectors usually fall open. Zeners (most semiconductors and carbon protectors) fail short and their no guarantee they won't burn a trace so UL sometimes requires fuses on such devices. Regards, Fred Townsend From: "doug...@gmail.com" To: EMC-PSTC@LISTSERV.IEEE.ORG Sent: Sun, September 23, 2012 8:31:19 AM Subject: MOV failure detection Aside from all the regulatory issues of leakage current and nasty failure modes of MOVs. What methods have been used to detect a failed transient suppression device in equipment? Or, is there some expectation the devices will survive a warranty period and that alone is good enough? Seems like any detection schemes would also have a series of regulatory issues and be a significant cost adder to the product. Doug Douglas E Powell Independent Compliance Consultant http://www.linkedin.com/in/dougp01 http://www.linkedin.com/in/dougp01 - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Appropriate ETSI standard for 433 MHz Band Radio
In the US the hams are secondary to the military. Also allowed are RFID tags and police robots as non-interfering tertiary users. Fred Townsend From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Charlie Blackham Sent: Monday, August 20, 2012 5:42 AM To: itl-emc user group; EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: Appropriate ETSI standard for 433 MHz Band Radio David Look at European Frequency Allocations in CEPT ERC report 25, http://www.erodocdb.dk/docs/doc98/official/pdf/ERCRep025.pdf. 433 MHz is allocated as an Amateur Radio Band, EN 301 783. Regards Charlie From: itl-emc user group [mailto:itl...@itl.co.il] Sent: 20 August 2012 13:20 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Appropriate ETSI standard for 433 MHz Band Radio Hello, Any ideas for the appropriate R&TTE radio standard for a 433 MHz band, 0.5W conducted RF power, radio device? Any ideas will be appreciated. Regards, David Shidlowsky | Technical Writer Address 1 Bat-Sheva St. POB 87, LOD 71100 Israel Tel 972-8-9186113 Fax 972-8-9153101 Mail e...@itl.co.i/dav...@itl.co.ill Web <http://www.itl.co.il> www.itl.co.il <http://app.sqm.co.il/SitePages/Questionnaire.aspx> Fill out Customer Satisfaction Survey - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Light Bulb provokquium
The dirty little secret in the Central California Coast is there is a lot more mercury in the soil from natural sources than CFLs but we will blame industrial polutsion for both. Fred Townsend DC to Light CFLs do have a dirty little secret with regard to the environment. They increase the amount of mercury in the landfill. Most countries have an exemption for this in their waste products legislation. -doug On 8/24/12, Pearson, John wrote: > Hi John > > Thanks > > My thinking is it isn't just price $'wise but also price to the environment > in both material and energy? > > JohnP > > -Original Message- > From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of John > Woodgate > Sent: 24 August 2012 16:25 > To: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] Light Bulb provokquium > > In message > , > dated Fri, 24 Aug 2012, Doug Powell writes: > >>Make the alternative bulbs economically competitive and dump the >>legislation. > > Chicken and egg; the industry wouldn't have spend a lot of R&D $$$ on CFLs > and LED lamps if the ban hadn't been introduced. Prices are coming down, but > not equal yet. > -- > OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk > Instead of saying that the government is doing too little, too late or too > much, too early, say they've got is exactly right, thus throwing them into > total confusion. > John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > > - > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. To post a message to the list, send your e-mail to > > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in > well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ > Instructions: http://listserv.ieee.org/request/user-guide.html > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas > Mike Cantwell > > For policy questions, send mail to: > Jim Bacher: > David Heald: > > - > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. To post a message to the list, send your e-mail to > > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in > well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ > Instructions: http://listserv.ieee.org/request/user-guide.html > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas > Mike Cantwell > > For policy questions, send mail to: > Jim Bacher: > David Heald: > -- Thanks, -doug Douglas E Powell doug...@gmail.com http://www.linkedin.com/in/dougp01 - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: From: Doug Powell To: "Pearson, John" Cc: EMC-PSTC@LISTSERV.IEEE.ORG Sent: Fri, August 24, 2012 10:29:53 AM Subject: Re: [PSES] Light Bulb provokquium - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), lar
Re: [PSES] EN 61000-4-5
Thanks for the replay Derek. Please see comments inline. From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Derek Walton Sent: Wednesday, August 01, 2012 8:15 PM To: ftowns...@sbcglobal.net; j...@randolph-telecom.com; gary.mcintu...@esterline.com; jrbar...@iglou.com; EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] EN 61000-4-5 Hi Fred, I think you are over reacting here a little, I don't believe anyone is saying a TVS is a current regulator. Derek I wouldn't have posted except for the repeated references to current such as 'of ESD diodes or TVS, they may limit the forward current to 24V'. The TVS I'm specifically dealing with is essentially a back to back Zener diode with the Die optimized for heat removal between two large electrodes. No disagreement here. You are incorrect saying that these must be used with other additional components. All surges have a defined source impedance, clip Derek you make my point. What defines the source impedance? The network. By network we are not talking about NBC or a LAN. We are talking about the L, C, and R that make up the circuit and connecting networks. Placing TVS directly across a high voltage source is certain death to the TVS as suggested elsewhere in the previous post. TVS are incapable of limiting current and therefore are dependent devices that rely on the network for current limiting. One can not insert them willy-nilly without first addressing the source impedance defining network. which is accounted for in the selection of the part. When you make 8 million a month of a part, you do not include a fraction of a cent more than necessary. If you have a SMPS, then by all means make use of the passive components to aid the TVS. OTOH, if you have a linear regulator, the only filter is for passing the immunity tests. TVS have applications way beyond cleaning up SMPS. There are literally millions of telephone line devices out there with linear power supplies that contain either TVS or gas tubes or both. The En 61000-4-5 spike is widely used, and I am lamenting manufacturers that do not list the current sink capability for this spike of their parts. One GOOD vendor ( others take note ) is ST. Check out Figure 5 here: http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATA SHEET/CD1367.pdf It would be most helpful if this chart were on all TVS data sheets. I agree they are nice parts with low inductance (also an undefined parameter). One nit-pick, I would not include a Zener as a TVS. Zeners are physically more designed for voltage regulation than the absorption of energy. clip Again we agree. Zeners have much lower peak pulse ratings and are optimized for voltage stability over varying currents. Maybe this is what you were thinking Fred? Not at all Derek. Best regards, Fred Townsend DC to Light Consulting Sincerely, Derek. L F Research -Original Message- From: Fred Townsend To: 'Joe Randolph' ; 'McInturff, Gary' ; jrbarnes ; EMC-PSTC Sent: Wed, Aug 1, 2012 9:40 pm Subject: RE: [PSES] EN 61000-4-5 Hi Joe: I have no quibble with your definition of TVS nor extending the term of TVS to surge devices like gas tubes which are both fast and surge capable. My objection is terming to TVS as current regulators or the idea they can be analyzed as standalone devices. The base parameters of the TVS must be summed with the network values, such as inductance, capacitance, and resistance to ascertain their performance levels. Best regards, Fred Townsend From: emc-p...@ieee.org [mailto:emc-p...@ieee.org <mailto:emc-p...@ieee.org?> ] On Behalf Of Joe Randolph Sent: Wednesday, August 01, 2012 6:11 PM To: Fred Townsend; 'McInturff, Gary'; jrbar...@iglou.com; EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: [PSES] EN 61000-4-5 Hi Fred: I think that for many people in the industry, the term "TVS" means, simply, "Transient Voltage Suppressor." In this context, "TVS" is just a descriptive term that can be taken to encompass any device that is used to suppress transient voltages. Under this broad definition, devices such as zener diodes, MOVs, sidactors, and even gas tubes could be legitimately characterized as TVS devices. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.com <http://www.randolph-telecom.com/> Gentlemen: My head is swimming. Forgive me for criticizing but TVS don't limit any current. They are fast transient voltage clamps designed to be members of inductive networks. The clamps are often used to suppress ringing where symmetry is of no concern. See YouTube: http://www.youtube.com/watch?v=5cXUTKg2T1A TVS are optimized for speed and therefore not very good surge suppressors. Their voltage rating is usually pegged just above the circuit sustaining voltage. Capacit
Re: [PSES] EN 61000-4-5
Hi Joe: I have no quibble with your definition of TVS nor extending the term of TVS to surge devices like gas tubes which are both fast and surge capable. My objection is terming to TVS as current regulators or the idea they can be analyzed as standalone devices. The base parameters of the TVS must be summed with the network values, such as inductance, capacitance, and resistance to ascertain their performance levels. Best regards, Fred Townsend From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Joe Randolph Sent: Wednesday, August 01, 2012 6:11 PM To: Fred Townsend; 'McInturff, Gary'; jrbar...@iglou.com; EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: [PSES] EN 61000-4-5 Hi Fred: I think that for many people in the industry, the term "TVS" means, simply, "Transient Voltage Suppressor." In this context, "TVS" is just a descriptive term that can be taken to encompass any device that is used to suppress transient voltages. Under this broad definition, devices such as zener diodes, MOVs, sidactors, and even gas tubes could be legitimately characterized as TVS devices. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.com <http://www.randolph-telecom.com/> Gentlemen: My head is swimming. Forgive me for criticizing but TVS don't limit any current. They are fast transient voltage clamps designed to be members of inductive networks. The clamps are often used to suppress ringing where symmetry is of no concern. See YouTube: http://www.youtube.com/watch?v=5cXUTKg2T1A TVS are optimized for speed and therefore not very good surge suppressors. Their voltage rating is usually pegged just above the circuit sustaining voltage. Capacitive networks generally don't need transient suppression. MOVs are surge suppressors usually rated in KVA or joules of energy. See YouTube http://www.youtube.com/watch?v=gQ5hHBVWOB4 <http://www.youtube.com/watch?v=gQ5hHBVWOB4 > MOV handle much more energy at the expense of speed. Where transient and surge protection are needed (say lightning), then both TVS and MOVs are jointly used. Both TVS and MOVs are designed to be members of networks and don't work very well as standalone devices. OK I'll crawl back into my hole now. Fred Townsend DC to Light Insulting -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of McInturff, Gary Sent: Wednesday, August 01, 2012 4:21 PM To: 'jrbar...@iglou.com'; 'EMC-PSTC@LISTSERV.IEEE.ORG' Subject: RE: [PSES] EN 61000-4-5 Non symmetry is also the case of ESD diodes or TVS, they may limit the forward current to 24V, but the reverse might be 18 Vdc, and that varies from vendor to vendor even though they are rated on the data sheet similarly Gary -Original Message- From: John Barnes [mailto:jrbar...@iglou.com] Sent: Wednesday, August 01, 2012 3:55 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] EN 61000-4-5 Derek, I ran into a similar problem about six years ago, where a 10-30VDC product for use on earth-moving equipment had its DC power protected by a Microsemi 1.5KE51CA-T bidirectional transient suppressor. Applying a single -1kV EN 61000-4-5 surge between power and ground would short out the transient suppressor with fancy fireworks and lots of smoke. In the first page of the datasheet for the 1.5KE51CA-T http://www.microsemi.com/en/sites/default/files/SA4-15.pdf under Applications/Benefits is the comment: "Secondary lightning protection per IEC61000-4-5 with 2 Ohms source impedance: * Class 2: 1.5KE5.0A to 1.5KE24A or CA * Class 3: 1.5KE5.0 to 1.5KE12A or CA" Our fix was to solder a second 1.5KE51CA-T in anti-parallel with the first one, which got us through the immunity requirements of EN 61326:1997 with no more problems. Apparently these transient protectors are bidirectional but not symmetrical-- their breakdown voltages and surge capabilities are different in the forward and backward directions. John Barnes KS4GL, PE, NCE, NCT, ESDC Eng, ESDC Tech, PSE, Master EMC Design Eng, SM IEEE dBi Corporation http://www.dbicorporation.com/ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list admini
Re: [PSES] EN 61000-4-5
Gentlemen: My head is swimming. Forgive me for criticizing but TVS don't limit any current. They are fast transient voltage clamps designed to be members of inductive networks. The clamps are often used to suppress ringing where symmetry is of no concern. See YouTube: http://www.youtube.com/watch?v=5cXUTKg2T1A TVS are optimized for speed and therefore not very good surge suppressors. Their voltage rating is usually pegged just above the circuit sustaining voltage. Capacitive networks generally don't need transient suppression. MOVs are surge suppressors usually rated in KVA or joules of energy. See YouTube http://www.youtube.com/watch?v=gQ5hHBVWOB4 MOV handle much more energy at the expense of speed. Where transient and surge protection are needed (say lightning), then both TVS and MOVs are jointly used. Both TVS and MOVs are designed to be members of networks and don't work very well as standalone devices. OK I'll crawl back into my hole now. Fred Townsend DC to Light Insulting -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of McInturff, Gary Sent: Wednesday, August 01, 2012 4:21 PM To: 'jrbar...@iglou.com'; 'EMC-PSTC@LISTSERV.IEEE.ORG' Subject: RE: [PSES] EN 61000-4-5 Non symmetry is also the case of ESD diodes or TVS, they may limit the forward current to 24V, but the reverse might be 18 Vdc, and that varies from vendor to vendor even though they are rated on the data sheet similarly Gary -Original Message- From: John Barnes [mailto:jrbar...@iglou.com] Sent: Wednesday, August 01, 2012 3:55 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] EN 61000-4-5 Derek, I ran into a similar problem about six years ago, where a 10-30VDC product for use on earth-moving equipment had its DC power protected by a Microsemi 1.5KE51CA-T bidirectional transient suppressor. Applying a single -1kV EN 61000-4-5 surge between power and ground would short out the transient suppressor with fancy fireworks and lots of smoke. In the first page of the datasheet for the 1.5KE51CA-T http://www.microsemi.com/en/sites/default/files/SA4-15.pdf under Applications/Benefits is the comment: "Secondary lightning protection per IEC61000-4-5 with 2 Ohms source impedance: * Class 2: 1.5KE5.0A to 1.5KE24A or CA * Class 3: 1.5KE5.0 to 1.5KE12A or CA" Our fix was to solder a second 1.5KE51CA-T in anti-parallel with the first one, which got us through the immunity requirements of EN 61326:1997 with no more problems. Apparently these transient protectors are bidirectional but not symmetrical-- their breakdown voltages and surge capabilities are different in the forward and backward directions. John Barnes KS4GL, PE, NCE, NCT, ESDC Eng, ESDC Tech, PSE, Master EMC Design Eng, SM IEEE dBi Corporation http://www.dbicorporation.com/ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ In
Re: [PSES] Slip Rings and EMI
David: John makes some very good points. A few more... Generally with brushes the higher the inductance and the higher the current the more arcing and higher EMI. Slip rings have been replaced by shaft encoders and hall effect sensors in many applications. In some feedback control systems the brush resistance may knowingly or unknowingly serve as the critical damping resistance for the loop making selection more difficult. Lubrication is a factor too. In other words brush selection is not the trivial task it might seem. Fred Townsend DC to Light -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of John Woodgate Sent: Thursday, May 03, 2012 10:35 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: Slip Rings and EMI In message , dated Thu, 3 May 2012, "David Carney (Neenah)" writes: >We?re considering a slip ring in a design to pass some wires through a >rotating motor shaft, and we have never used one before. Are there any >EMI concerns with this architecture? How much current and source voltage? This is critical, as different considerations apply according to these values. >If there are concerns, what types of mitigations are used for EMI when >slip rings are used? It can be a matter of 'art' - choosing the right brush and ring materials. Consult a brush manufacturer, e.g. Morgan. >If slip rings are to be avoided for certain types of signals due to EMI >concerns, what other alternatives should we consider? Rotary transformer, as in VHS VCRs. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Instead of saying that the government is doing too little, too late or too much, too early, say they've got is exactly right, thus throwing them into total confusion. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] 120 ohm CAN cable
Would you believe zip cord works pretty well ~ 90-110 ohms. Fred Townsend DC to Light From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of McInturff, Gary Sent: Tuesday, January 24, 2012 10:16 AM To: 'EMC-PSTC@LISTSERV.IEEE.ORG' Subject: 120 ohm CAN cable Can bus requires a 120 termination, and I have a client that is trying to do it with the bare cable, and I don't know that such cable exists unless custom built. I'm aware of impedance controlled coax but this is just your standard hookup cable in an appropriate jacket. We terminate the line at each end but don't control the cable itself. Yes there will be reflections but as I understand it the CAN standard identifies the termination requirements but doesn't identify a specific 120 ohm cable between the terminating resistors. Comments please? Gary McInturff Reliability/Compliance Engineer Esterline Interface Technologies Featuring ADVANCED INPUT, MEMTRON, and LRE MEDICAL products 600 W. Wilbur Avenue Coeur d'Alene, ID 83815-9496 Office:208-635-8306 Cell: 509 868 2279 Toll Free: 800-444-5923 X 1238 gary.mcintu...@esterline.com <mailto:brian.s...@esterline.com> <http://www.esterline.com/advancedinput> www.esterline.com/interfacetechnologies Technology, Innovation, Performance... - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
RE: [PSES] Standards for Motors and Wire in an outdoor environment
Jeff- Every situation is going to be different and must be individually evaluated. I think for motors, aside from the normal functional tests I would make a hipot to frame. Perhaps starting current draw if there is any gears and gear cases involved. You might want to do a hipot (insulation resistance) as well for the wire. More importantly would be an end to end resistance test. Be aware of the temperature coefficient of copper. It can be significant for long runs if the temperature varies significantly. Fred Townsend From: Jeff Collins [mailto:jeffcollin...@yahoo.com] Sent: Wednesday, February 25, 2009 1:28 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Standards for Motors and Wire in an outdoor environment Group, I have two questions. Can anyone recommend any standards ( Safety and Environmental) used to evaluate / qualify DC motors which reside in an outdoor environment? Can anyone advise on how you would evaluate/test copper wire after it has been exposed in a harsh outdoor environment? (Resistance, Continuity, Visual, etc ?) Thanks, Jeffrey Collins Compliance & Reliability Engineering - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: Domestic mains voltage
John I would disagree. I'm generalizing and there are exceptions to my statements. Incandescent light bulbs are fairly linear (at the high end). Computers and motors tend to be constant power. Ballasted devices (florescent lights) tend to be constant current which also translates to constant power. Obviously there is going to be some trade-offs but, overall, I would think the savings in copper losses would make the higher voltages more economical. Fred Townsend John Woodgate wrote: > clip... > > This advice seems to me a bit surprising. I suspect that a lot of the > load is linear, so that a higher voltage gives a HIGHER current, not a > lower current. I will ask some people about that. > >> Thru recent return record and investigation, the domestic mains >> voltage is at a higher side, > or = 250 Vac and the failure return >> rides up significantly. The manufacturers design their product at EU >> rated 230 Vac and assume the product operates at the highest voltage >> of 254 Vac occasionally. Now, the product is operating at the higher >> voltages all the time. It results in shortening its life or causing >> early failure. > > > Now that you know it's happening, you can, and of course should, > design with that in mind. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: Anechoic chambers: risks of energy leaking out
Gert: I don't think you'll find a list of important frequencies . If there were such a thing it would be like the terrorist handbook on how to bring down an airliner. I can tell you a lot of EMI immunity goes into every Boeing airplane. Fred Townsend From: Gert Gremmen To: Michael Heckrotte ; Frank Krozel ; emc-p...@ieee.org; emc-pstc@LISTSERV.IEEE.ORG Sent: Wednesday, January 14, 2009 10:17:18 PM Subject: Anechoic chambers: risks of energy leaking out Right. But still reduces the screening of your chamber from 100 dB or so to 30...40 and thus may cause problems with immunity testing. That brings me to a related subject: The risks that go with RF energy leaking out. Well if you are in the middle of Texas, that may not be such a problem. But my chamber is located precisely below the landing path of Rotterdam airport, and civil aircrafts like B737 fly approx. 150m (500ft) above it. Any idea what may happen, if a substantial amount of the right frequency leaks out at the right (?!?) moment ? Well, in fact I don't know. Is there someone on this list with pertinent data on this subject ?? Someone that can provide risk frequencies ? Gert Gremmen Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Michael Heckrotte Verzonden: donderdag 15 januari 2009 3:26 Aan: Frank Krozel; emc-p...@ieee.org; emc-pstc@LISTSERV.IEEE.ORG Onderwerp: RE: Anechoic Chamber: Pass-through on hydraulic lines All, As was stated some months or years ago on this list regarding this same topic: The waveguide pipe is an outer conducter, the wire going through it is a center conductor, and the combination of insulation/air is a dielectric; this configuration is also known as a coaxial cable = transmission line. If you absolutely must feed a wire or an ungrounded coax into a chamber, and the wire or coax ground cannot be filtered, then feed the wire or coax through two absorbing clamps, one inside the chamber and one outside the chamber. Place an absorbing clamp at each end of the waveguide pipe, butted up as close as possible to the waveguide pipe. This is effective over the frequency range at which the absorbing clamps provide decent common-mode decoupling. Best Regards, Mike Michael Heckrotte Director of Engineering Compliance Certification Services 47173 Benicia Street, Fremont, CA 94538 Main: (510) 771-1000 Direct: (510) 771-1121 Fax: (510) 661-0885 michael.heckro...@ccsemc.com From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Frank Krozel Sent: Wednesday, January 14, 2009 6:25 AM To: emc-p...@ieee.org Subject: Re: Anechoic Chamber: Pass-through on hydraulic lines All, Tim's comment made me think. In the past, I have seen hydraulic lines passed through waveguide feed-thrus that have re-inforced metal braid. Be aware of this if you need to pass hydraulic lines into your chamber or RF shielded enclosure. Alternatives do exist that are non-conductive. Regards Frank Krozel http://www.electronicinstrument.com From: Haynes, Tim (SELEX GALILEO, UK) To: emc-p...@ieee.org Sent: Wednesday, January 14, 2009 6:26 AM Subject: RE: Anechoic Chamber: Pass-through vs. Bulkhead Hi All, Conventional wisdom is, as stated, to bond the shield of a cable, hydraulic pipe, or any other electrically conductive - non-energised item that penetrates the shield wall. This is usually done with a purpose made "bulkhead" connector and is, again, usually done at a purpose made access plate in the shield room wall. Energised items cannot be connected to the shield and here the conventional wisdom is to connect the energised conductor via a filter that has its local ground connected to the shield wall. However, it might be acceptable to use a pass-through pipe where the pipe is long and can provide a sufficiently high capacitance to ground to form a functional filter at the frequencies of concern. The capacitance might be increased by "stuffing" the pass through pipe with conductive wire wool. I once had no option but to "pass through" a cable into the chamber. The project allowed me to remove the outer insulation at the pass through and I bonded the cable shield to the screened room by using a bolt to apply pressure to a shim of metal that held the cable firmly to the metal of the pass through pipe. That worked well. I hope the information helps. Regards Tim Tim Haynes A1N10 Electromagnetic Engineering Specialist SELEX Sensors and Airborne Systems 300 Capability Green Luton LU1 3PG ( Tel : +44 (0)1582 886239 7 Fax: +44 (0)1582 795863 ) Mob: +44 (0)7703 559 310 * E-mail : tim.hay...@selexgalileo.com P Please consider the environment before printing this email. There are 10 types of people in the world-those who understand binary and those who don't. J. Paxman SELEX Sensors and Airborne Systems Limited Registered Office: Sigma House, Christopher Martin Road, Ba
Re: EMC Eduction and Training
I think you hit the nail on the head when referring to deep roots. I think the color of the roots are green. I can remember tracing the steep decline in engineering enrollment during the eighties to statements like 'engineers cause pollution'. At the same time a salesman lambasted my conservative (engineering) approach to investment by stating, 'If it had been up to you engineers we would have never built the Golden Gate Bridge'. He was claiming credit for the salesmen! Now we have politicians who can't read a thermometer teaching global warming? I think engineering needs better PR. Fred Townsend DC to Light Cortland Richmond wrote: I see this as having deep roots. Many young people start College without the background to appreciate our discipline.These students have never listened to radio; they've only turned on a box or a compact player/stereo and stuck headphones in their ears. They will learn, if they take up engineering (Engineering? Yeah, they make lots of money; put me down for engineering.) about Faraday, Ohm, Volta , Hertz, Lenz and Maxwell, (MAYBE, about Farnsworth and Zworykin) but what they learn will not have reality to them beyond the mathematics necessary to describe certain physical phenomena they never expect to encounter. That may exaggerate -- a little. Well and all, they are more educated than I, even so. But I've been doing this work 25 years, and when in 1983, I walked into an EMC facility at Wang Labs in Massachusetts, I was able to do and understand the tests they needed done, never having done them before.It is amazing how little one need know, to know more than others. Maybe the schools need to hand out crystal sets. Or is it too late to awaken imaginations by then? Are these people going to school simply to make money? We are a distinct minority among the engineering staff where we work. We are a cost center, not a profit center, and often reminded of that. We're not romantic, We're not even attractive nerds. And schools must make money. Given that the marketplace doesn't make us look like a good bet, the institutions you found may be all the market will bear. Cortland, KA5S - Original Message - From: Alan E Hutley <mailto:a...@nutwooduk.co.uk> To: EMC-PSTC <mailto:emc-p...@ieee.org> Sent: 12/15/2008 10:19:16 AM Subject: EMC Eduction and Training Hello All I recently posted a request for information on Universities that offer EMC Educational activities. I thank those that responded but was very surprised by the very small number of Universities involved. I would like therefore to widen the debate. EMC Education and Training Behind EMC lays the Technology and Science of Electromagnetism, Signal Integrity and RF Engineering... EMC is a by-product of these disciplines. Over the past dozen or so years EMC has been largely, if not entirely, driven by Directives and Regulations. Around this scenario has evolved a specialised product industry together with consultants and soothsayers. Without the furore of this activity, EMC would almost certainly not have been on the RADAR to the extent that it has been. Could this be the reason why formal qualifications and academic training has not evolved at the same pace or magnitude? Is the apparent lack of resources committed to Training and Education due to the relevant organisations and Governments lack of understanding with respect to the complexity surrounding EMC... or are there other reasons. Invariably, or at least in many cases, Engineers seem to have ended up becoming EMC Engineers by default, not design. Does anyone actually set out with the sole purpose of becoming an EMC Engineer? Did you? I am interested in the views of others and finding out what resources are currently available, plus I would like to hear from Trainers, Educators, Course Presenters, EMC Engineers, Consultants and anyone else that can contribute to the debate by expressing their opinions. Thank you. Alan E Hutley The EMC Journal www.theemcjournal.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be po
Re: EMC Eduction and Training
I agree on the relevance of RF, SI, and EM to EMC since I do all three. I marvel that academia hasn't figured it out. I don't know of any schools that really tie them together. Perhaps it is because of the ways we address them. RF is tends toward frequency domain while SI tends to be time domain. Industry addresses both from the standpoint that they are needed to make the circuit work. On the other hand EMC is what is needed to sell the product. Except for the military, the industry attitude is not to prevent the problem (EMC) unless someone is complaining about the stink. The academic view is strange. I will never forget an advanced amplifier design class where I was supposed to calculate the proper value of a bypass capacitor. The 'correct' answer was 87.5 microfarads. Never mind you can't buy an 87.5 uF cap and therefore the design is unrealizable until proper tolerancing is applied. In terms of EMC the student is really sold down the river. For instance, switching regulators will be taught from the standpoint that either a capacitor or an inductor may be used to store energy. I have never seen a curriculum that tells the student inductors are much more likely to cause EMC problems than a capacitor. Fred Townsend DC to Light Alan E Hutley wrote: Hello All I recently posted a request for information on Universities that offer EMC Educational activities. I thank those that responded but was very surprised by the very small number of Universities involved. I would like therefore to widen the debate. EMC Education and Training Behind EMC lays the Technology and Science of Electromagnetism, Signal Integrity and RF Engineering... EMC is a by-product of these disciplines. Over the past dozen or so years EMC has been largely, if not entirely, driven by Directives and Regulations. Around this scenario has evolved a specialised product industry together with consultants and soothsayers. Without the furore of this activity, EMC would almost certainly not have been on the RADAR to the extent that it has been. Could this be the reason why formal qualifications and academic training has not evolved at the same pace or magnitude? Is the apparent lack of resources committed to Training and Education due to the relevant organisations and Governments lack of understanding with respect to the complexity surrounding EMC... or are there other reasons. Invariably, or at least in many cases, Engineers seem to have ended up becoming EMC Engineers by default, not design. Does anyone actually set out with the sole purpose of becoming an EMC Engineer? Did you? I am interested in the views of others and finding out what resources are currently available, plus I would like to hear from Trainers, Educators, Course Presenters, EMC Engineers, Consultants and anyone else that can contribute to the debate by expressing their opinions. Thank you. Alan E Hutley The EMC Journal www.theemcjournal.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald
Re: Common-mode emissions from SMPS
First you seem to condemn all SMPS to common mode emissions. Far from true. Most switching power supplies (at least the smaller ones) rectify the line and then use higher frequency DC to DC converters. It saves iron and with modern fast components you don't lose much in efficiency due to using higher frequencies (20 to 500KHz). The converter frequencies don't propagate much because they have to go through the big rectifier filer first. The problem occurs when we add power factor correction (PFC). Instead of straight rectification the AC current is taken out of the line in chunks. This produces lots of harmonics. Symmetry tends to cancel out the even harmonics but the odd ones propagate, particularly along the neutral in three phase systems. Since 3 phase neutrals are not expected to carry much current they are sometimes built smaller than the line circuits. It's all the perfect formula for emissions. Lack of symmetry and the UNCOMMON mode means they are very hard to filter. So it's not the SMPS and it's not common mode, it's the PFC. No good deed goes unpunished. Fred Townsend DC to Light John Woodgate wrote: > SMPS seem to be very good at producing common-mode emissions on all > the cables attached to them and the products they power. Would someone > please give me a simple explanation of how these common-mode emissions > are generated? > > I don't get involved with the internals of SMPS, and I've been given > some explanations that are both contradictory and, taken one at a > time, not terribly credible. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: Recommendations requested: Water chiller companies in N. California
Many on your list are not Silicon Valley but they serve Silicon Valley. Caveat Emptor. Perhaps you are looking in the wrong places. There are several HVAC and electrical companies in the Valley that do that sort of work. The key words are HVAC not water chillier. They are as close as the Yellow Pages. I don't know what kind of testing you are doing but chilled water is not normally used because it limits the low end to about 4 degrees C. If you are talking about water cooled mechanical that can be attached to some existing HVAC systems. The choice of systems is highly dependent on volume and range. N2 and CO2 systems are widely used for shocking and are easy to setup. They are expensive relative to mechanical so they are not normally used for production. Fred Townsend DC to Light Marko Radojicic wrote: Hello Group, We are looking to buy a water-cooled environmental chamber which requires an external water chiller for maximum performance. None of our potential vendors offers a turn-key solution however. Does anyone have first-hand recommendations with a chiller company that services Silicon Valley? The following link lists 25 companies which is 22 too many for me to follow up with. I’d really like to narrow the list down first. We are looking for, what else, high quality and low cost. http://www.thomasnet.com/northern-california/chillers-13936489-1.html Thanks, Marko Marko Radojicic Manager, Qualifications and Regulatory StrataLight Communications, Inc. 151 Albright Way Los Gatos, CA 95032 mradoji...@stratalight.com Desk: 408.385.3033 Cell: 650.575.3865 CONFIDENTIALITY This e-mail message and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail message, you are hereby notified that any dissemination, distribution or copying of this e-mail message, and any attachments thereto, is strictly prohibited. If you have received this e-mail message in error, please immediately notify the sender and permanently delete the original and any copies of this email and any prints thereof. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald
Re: Connecting DC output to earth ground
I'm wondering if something was missed here. In the telephone world +48 is grounded... NOT -48V. Mixing telephone systems with other systems where there are negative grounds like POE could certainly lead to smoke. The fact you have a resistor to ground is meaningless. What is the value of the resistor? Isn't one side of all shunt loads connected to ground? Fred Townsend Joe Randolph wrote: On 11/10/2008, Mark Gandler wrote: here is the case: Switch powered by 100-230VAC/48DC-1A adapter with earthed plug. At 48V side, "Vcc-" is connected through resistor directly to Earth ground. This switch has PoE port, which is used to power external device (PD, powered device), when there is a laptop connected through RS232 port to this PD. Laptop has his own power adapter, I assume grounded as well. In certain scenario, powered device in the middle, will get smoked. One claims it is due to the ground loop, based on Vcc- of power adapter being directly tied to chassis ground. Problem goes away after the connection is cut. Few questions: 1. are where any 60950 issues which could prevent tying DC(-) output to earth ground? (adapter has UL, TUV/CB certificates) 2. assuming the answer to #1 is "no", would this scenario require switch adapter and laptop adapter to be connected to different grounds? in order to create different potentials? and thus will make powered device in the middle the weakest point in the system? Hi Mark: >From your description, I'm not sure I quite understand the configuration you describe, but I can offer a few comments that may help you sort this out: 1) The basic IEEE 802.3 Ethernet specification requires 1500 VRMS isolation between the Ethernet cable lines and earth ground. This is primarily a functional requirement, not a safety requirement. It prevents ground loops that could otherwise occur if the equipment at the two ends of the cable run (up 100 meters) has two different ground references. 2) When power over Ethernet (POE) was added in IEEE 802.3af, the requirement for 1500 VRMS isolation was retained. So, POE interfaces (both the power-sourcing PSE and the powered-device PD) are each still supposed to be isolated from ground. This is typically done with isolated DC/DC converters. 3) The power supply for a laptop computer may or may not pass earth ground >from the AC mains outlet up to the laptop. That choice is up to the manufacturer. So, there should not be any path to ground from any Ethernet port, whether it be standard Ethernet, POE PSE, or POE PD. For an RS-232 port on a laptop, there may or may not be a connection to ground through the power supply. The fact that the 48 VDC supply to the switch is grounded does not necessarily mean that the power placed on the PSE Ethernet ports is also grounded. There might be (and should be) an isolated DC/DC converter inside the equipment for powering the PSE Ethernet ports. Even if the manufacturer of the switch violated the 802.3af isolation requirement, you still couldn't get a ground loop via the Ethernet connection unless the manufacturer of the PD also violated the 802.3af isolation requirement on the PD. This seems unlikely, unless the same errant manufacturer made both devices. Regarding your question about 60950 issues, there are none that I am aware of. I believe that POE is typically treated as a SELV circuit under 60950. The only place where you find an isolation requirement for POE is in IEEE 802.3af, which is only an industry standard as opposed to the regulatory standard 60950. I hope the above comments are helpful. The behavior you describe does sound like a possible ground loop problem, but properly designed POE equipment should prevent ground loops. It would be interesting to check the internal designs of the POE equipment to see if it is, in fact, isolated. It would also be interesting to determine what specific components are getting "smoked." Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.com <http://www.randolph-telecom.com/> - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org
Re: Li-Ion battery questions
Connected in serial? That's odd? If you are looking for a simple yes or no answer you are going to be disappointed. There are many factors effecting your question and you have barely scratched the surface with the data you have supplied. There are many approval hoops too. I'd start with regulations for air transport of lithium batteries. Fred Townsend DC to Light From: Anders Svensson B To: "emc-p...@ieee.org" Sent: Thursday, September 4, 2008 11:10:41 PM Subject: Li-Ion battery questions Dear experts, We have a coming product that should have a Lithium-Ion battery pack (as back up power). Is it allowed to have the battery installed in the product (the battery pack is located outside the products enclosure and connected in serial with the products AC/DC Power supply) during transportation to worldwide customers? Any input is very greatful! Thanks in advance! Regards Anders - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ <http://www.ieee-pses.org/> To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html <http://listserv.ieee.org/request/user-guide.html> List rules: http://www.ieee-pses.org/listrules.html <http://www.ieee-pses.org/listrules.html> For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc <http://www.ieeecommunities.org/emc-pstc> - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Another Cancer Scare?
Ged, I think this is one of those situations where the answer is somewhere in between. Yes registration can take less than a second. There are also lots of processes, like receiving a text message, that can take longer. The information is bursted and there is a lot of effort to minimize transmission length and power level to reduce exposure and extend battery life. As you observed it's still in seconds. Fred Townsend Dean Gerard (Medical Physics) wrote: Is it really only milliseconds? When my phone is in my desk drawer, or jacket pocket on the back of my chair, I am aware that it is periodically active because of interference it generates on the speakers of my PC. These bursts of audible interference are brief - but measurable in seconds rather than milliseconds. Ged Dean From: dBaron [mailto:d.ba...@ieee.org] Sent: Wednesday, July 30, 2008 12:00 PM To: Tang, George; 'Monrad Monsen' Cc: emc-p...@ieee.org Subject: RE: Another Cancer Scare? Sir: The intermittent, registration communications between a mobile phone and its base station are milliseconds in duration at intervals of 5-10 minutes; minimal exposures. Regards, Dave Baron, PE Consulting Engineer Electromagnetic Field Safety Austin, TX Voice: 512 917-8346 Fax: 206 203-0605 The information contained in this email may be the subject of public disclosure under the Freedom of Information Act 2000 - unless legally exempt from disclosure, the confidentiality of this email and your reply cannot be guaranteed. Copyright of this email and any attachments created by us remains vested in the Nottingham University Hospitals NHS Trust. This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. This footnote also confirms that this email message has been swept by security software for the presence of known computer viruses. Nottingham University Hospitals NHS Trust City Hospital campus | Hucknall Road | Nottingham | NG5 1PB | Tel: 0115 969 1169 QMC campus | Derby Road | Nottingham | NG7 2UH | Tel: 0115 924 9924 If you have received this email in error please notify the sender. ID:QMCICT1 - B48997d7b.0001.0001.mml - 11:31:23 08/06/08 - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Another Cancer Scare?
George I don't believe so. For the cell phone the mating ritual begins with a cell tower beacon. The phone replies to the beacon. No beacon no dance. Fred Townsend DC to Light Tang, George wrote: Sir, Is there any possibility that your cell phone can go into a mode that it starts to send the registration signal continuously if you are in a “dead zone” (or you are surrounded by metal cabinets in all directions)? Can a cell phone malfunction and go into this mode? Thanks, George From: dBaron [mailto:d.ba...@ieee.org] Sent: Wednesday, July 30, 2008 12:00 PM To: Tang, George; 'Monrad Monsen' Cc: emc-p...@ieee.org Subject: RE: Another Cancer Scare? Sir: The intermittent, registration communications between a mobile phone and its base station are milliseconds in duration at intervals of 5-10 minutes; minimal exposures. Regards, Dave Baron, PE Consulting Engineer Electromagnetic Field Safety Austin, TX Voice: 512 917-8346 Fax: 206 203-0605 From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Tang, George Sent: Wednesday, July 30, 2008 1:53 PM To: Monrad Monsen; emc-p...@ieee.org Subject: RE: Another Cancer Scare? This is very good information. But has any one done any study on the effects (if any) of cell phone fields on body internal organs? We know that cell phones make intermittent communications with cell towers even when they are not in use. Therefore, by simply carrying the cell phone with us, we are already exposed to the cell phone transmitting energy. Thus, it really does not matter if we are making long calls or short calls – we are being radiated 24 hours a day by just wearing the cell phone on the body. Thanks for addressing this. George Tang From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Monrad Monsen Sent: Tuesday, July 29, 2008 7:18 PM To: emc-p...@ieee.org Subject: RE: Another Cancer Scare? This has been an interesting discussion. There is definitely a lot of interest in this subject. Our EMC chapter in Denver heard a talk on this subject from an EMC Society Distinguished Lecturer (Dr. Michel Ianoz) on July 26, 2004. This presentation addressed the subject of "Biological and Health Effects of Electromagnetic Fields" in a very organized and detailed manner using three approaches: * Calculation and measurement (engineers) * Biological effects (biologists and engineers) * Effects on health (medical doctors and statisticians) I was impressed with the variety of approaches that have been used to study the topic. He concluded that more studies needed to be done, but basically the health risk is at such a low level that it is difficult to evaluate. This contrasts greatly from the clear health risks of heavy smoking. But we should be concerned when we see that moss growth and other biological organisms are affected when exposed to electromagnetic energy. Certainly, the power limits and restrictions used today greatly reduce this concern. I have no problems using cell phones next to my ear for short calls, but I prefer to use an ear bud or the speaker phone function for longer calls to keep the phone farther >from my brain. By going to our chapter web site, you can see the record of the meeting (http://www.ewh.ieee.org/r5/denver/rock mountainemc/archive/2004/July/index.html) and the actual slides he presented (http://www.ewh.ieee.org/r5/denver/rock mountainemc/archive/2004/July/bioeffect.pdf). Enjoy! Monrad Monsen Chairman, Rocky Mountain Chapter of EMC Society (RMCEMC) of IEEE -- Monrad L. Monsen Compliance Program Manager Storage Group Sun Microsystems monrad.mon...@sun.com 303.272.9612 Office - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...
Re: Another Cancer Scare?
This discussion may be delayed but I suspect it will go on for a long time. What next cell phones as a weapon? Opps, sorry they are already used in IEDs. How about long range popcorn popping? See http://en.wikipedia.org/wiki/Active_Denial_System. If this will give you a headache, surely the lawsuits for brain cancer can't be far away. Fred Townsend DC to Light Gert Gremmen wrote: To end this discussion (??!??), my opinion about this subject: EM fields of different frequencies and power levels will probably impact our body. So does eating salt, fat food, driving cars and talking loud. Reading email is probably harmful to your eyes. Mains harmonics will cause induced currents in your body; doctors and physicians will sooner or later day prove a correlation between cancer and cell phones. The same correlation they found between eating meat and cancer, and between most of the actions of life and cancer. I think most of these correlations are within the noise margins of risk and life. Each factor exists and is true, but is small compared to the total risk, and even more important, removing one source of cancer risk won’t reduce the total risk. (like summing 100 noise sources, and removing one) Annihilating all sources of cancer is impossible, and we have to live with the fact that now and then one of us is to die early because of cancer. We live on a dangerous planet, radiated by damaging sun radiation, dangerous natural radio-activity, stress causing partners and children to live with, and all kinds of small risks of dangerous nature. If you cannot live with the risk of cancer from your cellular, stop crossing roads and driving cars, flying planes and eating at MacDonald’s. Stop living. If there were a substantial risk on cancer by exposure to EM-waves, this would have been proven without doubt a long time ago. Like happened for radio-activity. The “inventor” of radio-activity (M. Curie) died of it. Like the substantial risks caused by exposure for certain chemicals and cancer. Wise design incorporates reducing any source of energy impacting the human body, for numerous reasons, not just cancer. Low power transmitters allow for longer standby time, and smaller batteries, reducing environmental impact and increasing quality of the product, as well as lower costs, and yes , preventing costly investigations that have been done over and over, trying to quantify a neglectable effect. Gert Gremmen Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Tang, George Verzonden: Wednesday, July 30, 2008 9:19 PM Aan: d.ba...@ieee.org CC: emc-p...@ieee.org Onderwerp: RE: Another Cancer Scare? Thank you. George From: dBaron [mailto:d.ba...@ieee.org] Sent: Wednesday, July 30, 2008 12:00 PM To: Tang, George; 'Monrad Monsen' Cc: emc-p...@ieee.org Subject: RE: Another Cancer Scare? Sir: The intermittent, registration communications between a mobile phone and its base station are milliseconds in duration at intervals of 5-10 minutes; minimal exposures. Regards, Dave Baron, PE Consulting Engineer Electromagnetic Field Safety Austin, TX Voice: 512 917-8346 Fax: 206 203-0605 From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Tang, George Sent: Wednesday, July 30, 2008 1:53 PM To: Monrad Monsen; emc-p...@ieee.org Subject: RE: Another Cancer Scare? This is very good information. But has any one done any study on the effects (if any) of cell phone fields on body internal organs? We know that cell phones make intermittent communications with cell towers even when they are not in use. Therefore, by simply carrying the cell phone with us, we are already exposed to the cell phone transmitting energy. Thus, it really does not matter if we are making long calls or short calls – we are being radiated 24 hours a day by just wearing the cell phone on the body. Thanks for addressing this. George Tang From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Monrad Monsen Sent: Tuesday, July 29, 2008 7:18 PM To: emc-p...@ieee.org Subject: RE: Another Cancer Scare? This has been an interesting discus
Re: Another Cancer Scare?
Chris Wells wrote:
Fred - I would argue that you can see significant harmonics in comercial
buildings in the USA.
I guess I didn't make myself very clear. I did not mean to say that a 3 phase
load was required to produce harmonics. Quite the contrary. The harmonics are
created in unbalanced loads in three phase systems. A three phase motor, like
what would be found in an air-conditioning system would be a balanced load. A
switching power supply across one leg of a three phase system (system being
the operative word) is a harmonic generator. The harmonics are propagated
through the transformers (particularly open delta) and along the neutral
(stinger) in a wye. Non-linearites in single phase 240/120 systems can cause
harmonics too. This is usually seen when the transformer is operating at near
or full capacity.
Single phase power supply loads without Power Factor Correction front
ends
can create 3rd harmonics ~ equal in size to the fundamental.
The higher order harmonics dropping off in magnitude in a sinx/x
function.
The use of PFC front ends on PCs in the USA should be curbing much of
this.
This may or may not be the case. Some PFCs actually make the system efficiency
and harmonics worse! That is because a PFC will try and correct on its input
side as well as it's load side. For example lets say you have two loads with a
PF of 0.9. One of the loads has a PFC and the other one doesn't. The PFC will
correct its own load and the other (no PFC) load as well. Instead of
decreasing current (and ohmic losses) it actually increases current (over a no
PFC system). The further the uncorrected load is from the PFC the worse the
problem.
Fred Townsend
DC to Light
I suspect that the higher frequency mag field exposure in the office
enviroment is low.
Chris
- Original Message -
From: Fred Townsend <mailto:ftowns...@sbcglobal.net>
To: Tang, George <mailto:george.t...@lsi.com>
Cc: John Woodgate <mailto:j...@jmwa.demon.co.uk> ;
emc-p...@ieee.org
Sent: Tuesday, July 29, 2008 4:02 PM
Subject: Re: Another Cancer Scare?
George, thank you for your citations. Someone once wrote, "If
you want to
understand what is going on, follow the money." When I Google your citations
the ads from lawyers to join class action lawsuits on cell phones pop up. So
far what I read doesn't pass the smell test.
I have personally researched harmonics on power systems. They
are not that
common. They typically occur with 3 phase systems where switching power
supplies are used which means computer centers and the like. Computer centers
are a controlled environment where they try to keep the people away so they
won't pollute the computers. Commercial power lines are almost always in
conduit which means they are shielded as well. After all computer rooms are
full of magnetic media. (You wouldn't want to damage the media would you?) You
really have to work at finding low frequency harmonics that impinge on people.
By definition harmonics are smaller than the fundamental which
means if you
start with a small fundamental the harmonics are going to be even smaller. It
is common to increase the dosage to accelerate cancer testing so why not use
strong fields to accelerate the test. This is easy to do in the lab but
difficult to do if you are using observation data from real life. Of course if
you are using real life data, it is no longer a controlled environment.
There is good money to be made if you can claim to be an expert
witness that
has seen cancer cells caused by magnetic fields. It is not surprising then
that people will stand up in court and perjure themselves. In court, experts
can give opinion in place of facts which is something ordinary people can't
do. In the case of juries isn't it interesting that people that know nothing
about the subject at hand are given the final say.
Fred Townsend
DC to Light
Tang, George wrote:
John,
You have provided very good info. My comment is that
the fields used in
the experiments are relatively weak, in the range of a few microT to 1800
microT, and the durations are relatively short (a few days). Researchers have
found that when they increase the field strength up to 100 milli-G for months
up to 1 year, the results show an increase in cancer cells growth.
George
-Original Message-
From: emc-
Re: Another Cancer Scare?
George, thank you for your citations. Someone once wrote, "If you want to understand what is going on, follow the money." When I Google your citations the ads from lawyers to join class action lawsuits on cell phones pop up. So far what I read doesn't pass the smell test. I have personally researched harmonics on power systems. They are not that common. They typically occur with 3 phase systems where switching power supplies are used which means computer centers and the like. Computer centers are a controlled environment where they try to keep the people away so they won't pollute the computers. Commercial power lines are almost always in conduit which means they are shielded as well. After all computer rooms are full of magnetic media. (You wouldn't want to damage the media would you?) You really have to work at finding low frequency harmonics that impinge on people. By definition harmonics are smaller than the fundamental which means if you start with a small fundamental the harmonics are going to be even smaller. It is common to increase the dosage to accelerate cancer testing so why not use strong fields to accelerate the test. This is easy to do in the lab but difficult to do if you are using observation data from real life. Of course if you are using real life data, it is no longer a controlled environment. There is good money to be made if you can claim to be an expert witness that has seen cancer cells caused by magnetic fields. It is not surprising then that people will stand up in court and perjure themselves. In court, experts can give opinion in place of facts which is something ordinary people can't do. In the case of juries isn't it interesting that people that know nothing about the subject at hand are given the final say. Fred Townsend DC to Light Tang, George wrote: John, You have provided very good info. My comment is that the fields used in the experiments are relatively weak, in the range of a few microT to 1800 microT, and the durations are relatively short (a few days). Researchers have found that when they increase the field strength up to 100 milli-G for months up to 1 year, the results show an increase in cancer cells growth. George -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of John Woodgate Sent: Friday, July 25, 2008 11:39 PM To: emc-p...@ieee.org Subject: Re: Another Cancer Scare? In message <4caa0df84cab184eb09525a5938e5c744e98a...@cosmail02.lsi.com> <mailto:4caa0df84cab184eb09525a5938e5c744e98a...@cosmail02.lsi.com> , dated Fri, 25 Jul 2008, "Tang, George" <mailto:george.t...@lsi.com> writes: There has been some research published in the last few years about power line harmonics inducing cancer in the human body. These are fields in the kHz to hundreds of kHz and currents in the range of tens of amps to hundreds of amps. There has also been a very great deal more research published that finds no such effects. See, for example: http://www.faqs.org/faqs/medicine/powerlines-cancer-faq/ If there were hundreds of amps at hundreds of kHz circulating in any power distribution system, it would collapse due to system capacitor heating and vast over-voltages on system inductors. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Either we are causing global warming, in which case we may be able to stop it, or natural variation is causing it, and we probably can't stop it. You choose! John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - -
Re: Another Cancer Scare?
Good point George. However I must point out blue tooth is much lower power at least twice the frequency, close to microwave ovens (another can of worms). Again I say this appears to be solicitation for a research grant. Fred Townsend DC to Light Tang, George wrote: By the way, the latest warning came from Dr. Ronald B. Herberman, director of the University of Pittsburgh Cancer Institute, talking to reporters on his CELL PHONE via a Bluetooth headset. Dr. Herberman also recommended others to do the same by using a wireless headset when talking on the cell. Now does Dr. Herberman not understand that a wireless headset also has a transmitting ANTENNA located right next to his HEAD and bombards his HEAD with EM WAVES? Or is this just a bad commercial to sell wireless headsets? Has he been paid to make these warnings? George Tang -Original Message- From: Derek Walton [mailto:lfresea...@aol.com] Sent: Friday, July 25, 2008 12:58 PM To: Lothar Schmidt Cc: Fred Townsend; Tang, George; IEEE EMC Discussion Group Subject: Re: Another Cancer Scare? Not wanting to appear silly, or spread rumors, but some of the thinking behind the potential for EM cancers was explained to me as follows: Cancers are mutant forms of normal cells. Such mutations occur when the cell reproduces. That process is more likely in the young, or where tissues are repairing. This is separate from cell damage through heating most often being considered when power levels are discussed. Part of the reproduction process is un-encoding the cell structure from the DNA, and that is influenced by fields which if great enough cause non intended cell structure. Usually the fields are magnetic because they penetrate deeper into skin tissue. Exposing non developing cells to fields would obviously never exhibit problems. A huge level of research to date has done just that... Other research is specifically looking at the influence on developing cells, I'm not sure yet how much of that is public domain. Again, I stress this comes from an aging guy... I may be remembering incorrectly, or understood the explanation wrong. We live in interesting times. Cheers, Derek Walton L F Research Lothar Schmidt wrote: Just for clarification, Cell phones with GSM technology transmit with 2W burst power @ 850MHz and with 1W burst power @1900 MHz CDMA and WCDMA technology uses 200mW output power. Regarding the influence of cell phones to a human being. My opinion is, that there are millions of cell phones used for so many years by a huge number of people and many of them seem to have the phone glued to the ear. If there is any impact we should have seen a significant increase in certain areas like cancer. This didn't happen therefore I believe the influence is close to none. Best Regards *Lothar Schmidt** *Director Regulatory & Antenna Services *CETECOM Inc.* 411 Dixon Landing Road Milpitas, CA 95035 Phone +1 (408) 586 6214 Fax +1 (408) 586 6299 email lothar.schm...@cetecomusa.com <mailto:lothar.schm...@cetecomusa.com> <mailto:lothar.schm...@cetecomusa.com> //This e-mail may contain proprietary, privileged and confidential information for the sole use of the named intended recipient. Any review or distribution of this e-mail by any party other than the intended recipient or that person's agent is strictly prohibited. If you are not the intended recipient, please delete all copies and immediately contact the sender. You must not, directly or indirectly, use, disclose, distribute, print, or copy any part of this message if you are not the intended recipient.// *From:* emc-p...@ieee.org [mailto:emc-p...@ieee.org] *On Behalf Of *Fred Townsend *Sent:* Friday, July 25, 2008 11:37 AM *To:* Tang, George *Cc:* Derek Walton; IEEE EMC Discussion Group
Re: Another Cancer Scare?
I agree with John but I want to further challenge several of Derek's statements. Derek Walton wrote: > > > Part of the reproduction process is un-encoding the cell structure > from the DNA, and that is influenced by fields which if great enough > cause non intended cell structure. Usually the fields are magnetic > because they penetrate deeper into skin tissue. > > What kind of field? What is your source? On your theory of developing cells why are the researchers concentrating on the relatively stable gray matter as this reference suggests? Skin cells are reproducing all the time, have shown sensitivity to uv, and are closer to the source. Fred Townsend DC to Light John Woodgate wrote: > In message <488a3037.4010...@aol.com>, dated Fri, 25 Jul 2008, Derek > Walton writes: > > >> Part of the reproduction process is un-encoding the cell structure >> from the DNA, and that is influenced by fields which if great enough >> cause non intended cell structure. > > > Allegedly. You have assumed what some people are trying to prove. > >> Usually the fields are magnetic because they penetrate deeper into >> skin tissue. > > > I'm not sure what you mean by that. Do you mean 'Researchers have > mostly used magnetic fields in experiments because they penetrate > tissue more than electric fields do'? > > Life on this planet has evolved in the presence of a fairly strong > magnetic field (about 40 A/m +/-15 A/m). Unless something is > completely still, there are induced electric currents as well as the > magnetic field. > >> >> Exposing non developing cells to fields would obviously never exhibit >> problems. A huge level of research to date has done just that... > > > You mean, a huge amount of research on dead things? In live animals > and plants, cells are dividing all the time. > >> >> Other research is specifically looking at the influence on developing >> cells, I'm not sure yet how much of that is public domain. > > > There have been reports of observed effects, but none seem to have > convinced the peer groups. Yet? - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Another Cancer Scare?
George, I'm no medical expert either but I think I understand a few laws of physics, Gauss's law, and Maxwell's equations in particular. If there is to be any effect on the human body, surely it must be directly from the magnetism or indirectly from the induced currents. To the best of my knowledge there never has been a demonstrated effect on the human body by magnetism. That leaves induced currents. Many ham and commercial handy talkies (HT) can put out 5 watts. When used, the rubber ducky runs right by the face or ears. From personal experiments I can say looking directly at the sun causes a noticeable heating effect while using my 5 watt HT @ 146MHz at night doesn't. The skin effect (not to be confused with human skin) means that almost none of the energy penetrates the skull at 146 MHz. If it doesn't penetrate, how can it cause an effect? As you point out modern cell phones put out much less power (<100 mW). Since the skin effect is much greater at cell phone frequencies, I don't think there is a snowball's chance of a cell phone causing damage to any part of the body with the possible exception of the eyes. There is anecdotal evidence that looking at a functional cell phone while driving can cause injury and even death to the whole body. Fred Townsend DC to Light Tang, George wrote: My personal opinion is that the research findings MAY have some valid points, however, the data they have is way out-dated. We know that in the late '80s, people use mobile phones that put out several watts of radiated power. In the early '90s when cell phones were just starting to appear on the market, most of them were still putting out more than 1 watt of radiated power. We have heard of technicians who worked on LAN equipment while talking on the cell phone, and the cell phone radiation induced data error in the Ethernet lines. Those were the days when the cell phone transmitted too much power. In the last few years, the goal of achieving longer talk time, thus lower power consumption, and the use of low voltage electronics due to the widely incorporation of sub-micron transistors have limited the cell phone transmitted power down to low mW range. The research is so far behind the improvements in technology that their findings are out-dated by the ne w products on the market today. Of course, I am not a medical expert in the cancer field, and I do not design or manufacture cell phones, so I certainly cannot speak for the experts in these areas. But I do know that these findings most likely are not applicable to the products out on the market today. George Tang -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Fred Townsend Sent: Thursday, July 24, 2008 12:09 PM To: Derek Walton Cc: IEEE EMC Discussion Group Subject: Re: Another Cancer Scare? I heard the interview. The doctor appeared to dodge the question as to proof. He did say more research was needed (Ignoring this subject has already been extensively researched.). It appeared to be a blatant attempt to get research funding. Fred Townsend DC to Light Derek Walton wrote: Does anyone know more about the research spoken about in the BBC news artical? http://news.bbc.co.uk/2/hi/health/7523109.stm Is it really new unpublisged research or just rehashing the old? Sincerely, Derek Walton L F Research - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at:
Re: Another Cancer Scare?
George, I'm no medical expert either but I think I understand a few laws of physics, Gauss's law, and Maxwell's equations in particular. If there is to be any effect on the human body, surely it must be directly from the magnetism or indirectly from the induced currents. To the best of my knowledge there never has been a demonstrated effect on the human body by magnetism. That leaves induced currents. Many ham and commercial handy talkies (HT) can put out 5 watts. When used, the rubber ducky runs right by the face or ears. From personal experiments I can say looking directly at the sun causes a noticeable heating effect while using my 5 watt HT @ 146MHz at night doesn't. The skin effect (not to be confused with human skin) means that almost none of the energy penetrates the skull at 146 MHz. If it doesn't penetrate, how can it cause an effect? As you point out modern cell phones put out much less power (<100 mW). Since the skin effect is much greater at cell phone frequencies, I don't think there is a snowball's chance of a cell phone causing damage to any part of the body with the possible exception of the eyes. There is anecdotal evidence that looking at a functional cell phone while driving can cause injury and even death to the whole body. Fred Townsend DC to Light Tang, George wrote: My personal opinion is that the research findings MAY have some valid points, however, the data they have is way out-dated. We know that in the late '80s, people use mobile phones that put out several watts of radiated power. In the early '90s when cell phones were just starting to appear on the market, most of them were still putting out more than 1 watt of radiated power. We have heard of technicians who worked on LAN equipment while talking on the cell phone, and the cell phone radiation induced data error in the Ethernet lines. Those were the days when the cell phone transmitted too much power. In the last few years, the goal of achieving longer talk time, thus lower power consumption, and the use of low voltage electronics due to the widely incorporation of sub-micron transistors have limited the cell phone transmitted power down to low mW range. The research is so far behind the improvements in technology that their findings are out-dated by the ne w products on the market today. Of course, I am not a medical expert in the cancer field, and I do not design or manufacture cell phones, so I certainly cannot speak for the experts in these areas. But I do know that these findings most likely are not applicable to the products out on the market today. George Tang -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Fred Townsend Sent: Thursday, July 24, 2008 12:09 PM To: Derek Walton Cc: IEEE EMC Discussion Group Subject: Re: Another Cancer Scare? I heard the interview. The doctor appeared to dodge the question as to proof. He did say more research was needed (Ignoring this subject has already been extensively researched.). It appeared to be a blatant attempt to get research funding. Fred Townsend DC to Light Derek Walton wrote: Does anyone know more about the research spoken about in the BBC news artical? http://news.bbc.co.uk/2/hi/health/7523109.stm Is it really new unpublisged research or just rehashing the old? Sincerely, Derek Walton L F Research - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at:
Re: caster safety
John in general I agree with you. The operative word here is minimum. Big is better unless you have a height problem. As I recall we were dealing with a 7' rack with 7' doorways. Obviously there is a trade off here. As I recall we started with 2" which had a very high rolling resistance on carpet. Fred Townsend DC to Light John Woodgate wrote: > In message <488766f7.1080...@sbcglobal.net>, dated Wed, 23 Jul 2008, > Fred Townsend writes: > > >> After [re]studying the issue the MEs came to the conclusion that six, >> 2.5" casters were minimum, > > > If 2.5" is the diameter, I would say that is too small. The ability to > negotiate obstructions without sudden decelerations is far better with > larger wheels. I would think that 4" might be more appropriate. My > bog-standard 19" rack x 80 cm lab trolleys have 3.5" and 4" wheels. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: opinions, please
drcuthb...@micron.com wrote: > I have a question: Is a Memory Module (DIMM) considered a component or an apparatus? As an engineer a DIMM is definitely a component. My mother, the computer user, would call it an apparatus. So the answer depends on how your ox is gourd. Fred Townsend > > > I'm trying to decide whether the CE MARK is applicable to this type of product. > >Dave Cuthbert >Micron Technology > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Component substitutions
Jeff I don't think I have ever seen the issue of component subs addressed before except by the FDA which says if you change anything you have to start all tests over again. I agree PCB or clock changes are a no brainier. Beyond that I would say any magnetic change... transformer, choke, etc. or mechanical changes such as the chassis or cover would be candidates for retest. Sometimes just turning a transformer 90 degrees will stop radiation so I must assume it could effect additional radiation as well. Fred Townsend "Bailey, Jeff" wrote: > Greetings group, > > Can any of you point me to some reference material that addresses component > changes and the effect of such changes on emission and immunity results. I > am aiming at bettering my understanding of how to evaluate when a re-test > should be applicable or when it may be overkill. > > I'd like to come up with some measurable means of classing component changes > ranging from drop in replacement parts requiring no PCB changes all the way > to the obvious re-test candidates of component changes clocked at different > rates and requiring many PCB changes. Are there any written rules to apply > or is it left as an engineering judgement call? > > Any help or guidance would be appreciated, online or offline. > > Thanks and regards, > > -Jeff Bailey > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: electrochemical potentials
I think you are confusing data and standards. Electrochemical potential is data that goes back over three centuries when Voltaire and others started measuring it. The first place I ever saw it published was in my father's copy of the "Handbook of Chemistry and Physics", 19th edition. by the Chemical Rubber Company. I used the log and trig tables in the "CRC" when slide rule accuracy wasn't good enough. BTW slide rules are analog calculators. Fred Townsend John Woodgate wrote: > I read in !emc-pstc that david_ster...@ademco.com wrote (in <2DF7C54A75B > dd311b61700508b64231008db5...@nyhqex1.ademconet.com>) about > 'electrochemical potentials' on Wed, 15 Oct 2003: > > >I am reviewing some dissimilar material combinations in an earthing > >path. I have reviewed a lot data available on-line and in a few > >reference texts. I would now like to better understand the origins of > >Table J.1 in IEC60950. > > > > >Does anyone know where the data on which Table J.1 is based originated? > > I didn't receive the original message. I found, several years ago, an > error in the table and at that stage tried to find out where it came > from, without success. > > > >Was it a reference standard or data from an industry association? > >Something else? > > It doesn't seem to come from another standard. > > > >I am finding Table J.1 might be useful as a reference, but little else. > >The types of alloys referenced can have electrochemical potential > >differences relative to one another that vary 10% or more from the > >values shown in the table. > > > >I'd appreciate any input you might have. > > It's not actually much use at all. These potentials give an indication > of the probability of electrolytic corrosion under *laboratory* > conditions, with no contaminants. They don't give reliable indications > in the real world, where contaminant ions, such as chloride, sulfide and > sulfate, occur. Having said that, avoiding combinations that involve > high potentials minimises the probability of serious short-term > corrosion, but by no means guarantees acceptable results. > -- > Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk > Interested in professional sound reinforcement and distribution? Then go to > http://www.isce.org.uk > PLEASE do NOT copy news posts to me by E-MAIL! > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Impulse for Hi-Pot
I think you make an apples to oranges comparison. The one watt rating is for cw, not pulse. A carbon composition resistor should be OK at 5 watts pulse. A couple of caveats. 1. Do not use wirewound resistors. (Magnetostrictive action will explode them.) 2. Do not use metal film, carbon film or any other laser trimmed types. (Power distributes unevenly) 3. Keep the duty cycle at 1% or less. Fred Townsend "HARDMAN, BRYAN" wrote: > Hello All, > > I have a request from the design community to implement a routine impulse > test in lieu of a Hi-Pot test. This product is evaluated to 61010-1 and the > reason for the request is that a measuring circuit connected to the affected > output circuit contains a resistor string that cannot withstand the power > delivered by the Hi-Pot test [4.6 kVdc across a mom resistor = 4.2 Watts. > (this is greater than the 1 Watt resistor rating)]. > > Anyone have experience replacing routine Hi-Pot testing with impulse > testing? > > Bryan Hardman > Advanced Energy > 970 407 6617 > > ___ > This message, including any attachments, may contain information > that is confidential and proprietary information of Advanced > Energy Industries, Inc. The dissemination, distribution, use > or copying of this message or any of its attachments is > strictly prohibited without the express written consent of > Advanced Energy Industries, Inc. > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Arcing & Sparking
I have never seen a really definitive statement about arcs and sparks however I tend to think of sparks as transient ( as in spark plugs) and arcs as sustained (as in arc lamps). Does that make sense? Fred Townsend "Speakman, Jim" wrote: > Fellow Listers > > At a recent equipment design review, a discussion on arcing and sparking > indicated a lack of definitive knowledge of the difference between an 'arc' > and a 'spark'. > > Is an 'arc', basically just a long 'spark'. If so, at what point > (precisely) does a 'spark' become an 'arc'? > > Have I got it all wrong? Are they 'something else'. > > Can anyone enlighten my darkness? > > __ > Jim Speakman > (Design Safety Representative (Southern Sites) > > Thales Defence Ltd > Thales Sensors > Manor Royal > Crawley > West Sussex > RH10 9PZ > > > * Tel:+44(0)1293 644911 > > * Mob:+44(0)7968 529439 > > * Fax : +44(0)1293 644194 > > *e-mail jim.speak...@uk.thalesgroup.com > > > __ > This e-mail contains confidential information for the addressee only. If a > transmission error has misdirected this e-mail, please notify us on > +44(0)1293 644911 and delete it and all copies from your system. You should > not use, disclose, distribute or copy this communication if received in > error. > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Synchronizing DC-DC converters to reduce emissions?
Pat Lawler wrote: > We are designing a switching power supply for a customer that has > multiple outputs. Due to the tight regulation requirements, all > outputs have their own PWM modulators and control loops. > > The customer feels the RF emissions (as measured by CISPR 11) will be > reduced by synchronizing the frequencies of all the converters. I > think synchronizing the PWM sections will make the total power supply > emissions as high as possible (emissions are coherent?). > > 1) What has been your experience with controlling noise from multiple > switching power supplies? Is synchronizing a good idea? > Synchronizing is a two edged sword as I think you have correctly surmised. It is a good technique at reducing EMI susceptibility where there are clocked processes such as logic and A to D conversion. The biggest problem is the PWMs will have a spectrum of emissions that varies as a function of load current. Synchronizing will make it easier measure emissions by eliminating the variable beat frequencies. This usually results in higher apparent emissions. > > 2) If the supplies are synchronized, would a phase shift between > converters (avoiding simultaneous switching of all converters) help? > Yes. Using a multi-phase clock will help. The biggest effect will be seen at light loads. As loading increases the PWM pulse widths will start to overlap and the emissions will go up. Overall I think synchronizing is a good idea. There is a way to test the hypothesis. Find a way to run each of the converters by itself. (I do this by replacing all the converters but the UUT converter, with linear lab supplies.) If any of the emissions of each individual supply is say greater than 6db above the others, synchronizing will have minimal effect. If all emissions are approximately equal, synchronizing will keep the levels close to the single converter values. Don't forget to test at all load levels. Fred Townsend > > Thanks, > --- > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Number of Terminations on a Ground Stud?
Are we talking about electrical circuits or electronic? If we are talking electrical there may be some concerns about current capacity that would limit the number. If we are talking electronic circuits returning all ground circuits to a common ground point is a considered good design practice. Fred Townsend "Momcilovic, Nick" wrote: > Is anyone familiar with any requirement that limits the number of ground > terminations on a single stud? I heard that the limit is two per stud but I > was not able to confirm this with any of the standards we have. > > Thanks in advance for your help. > > Sincerely, > > Nick Momcilovic > Product Safety > > Quad/Tech, Inc. > A Subsidiary of Quad/Graphics > > Sussex, Wisconsin > 414-566-7915 phone > 414-566-9576 fax > nick.momcilo...@qtiworld.com > www.qtiworld.com > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: US Central Office power source
While I doubt there are any offices that use -60 as a standard, the standard 48 +/- 8 VDC gets you pretty close. I think most of the new smaller offices use -24 +/- 4 as a standard. Our company avoided stocking two supplies by designing a supply with a -18 to 70V VDC input range. Fred Townsend Anil Allamaneni wrote: > Greetings, > > Are there *any* CO locations in US that use -60VDC? I > am assuming 99.999% of all CO's in US use -48VDC. > > Thanks. > > Anil > a...@occamnetworks.com > > __ > Do you Yahoo!? > SBC Yahoo! DSL - Now only $29.95 per month! > http://sbc.yahoo.com > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Surge Suppressors on a UPS
Chris Maxwell wrote: > Fred, > > Maybe you're right. Do UPSs protect against lightning surge? Your question resolves into two issues: 1) Marketing Hype 2) Reality 1) I have seen some marketing hype that says their UPS will do everything to protect your system and wash the windows while it is at it. I think we know BS when we read it. 2) The reality is lightning is called an "Act of God" for good reason. Many of the things that determine whether you are protected from a lightning strike depend on circumstances beyond your control like how far are you from the strike, how far are you from the mains, and how conductive is the ground you walk on. I think one of the better UPSs out there recognizes no one can guarantee protection from "Act of God" but they do offer a free insurance policy to replace your equipment if it fails due to a lightning strike when connected to their UPS. Now that's putting your money where your mouth is. Fred Townsend > I know that they protect against low frequency, low magnitude voltage dips and surges. However, I'm unsure of their ability to protect against lightning surge. > > If the UPS is specified by its manufacturer to protect against lightning surge; then my question is moot. Even so, I would still wonder, does the UPS guarantee that the UPS and the equipment attached to it would survive the surge? Or does the UPS sacrifice itself in order to protect its load? > > If there is any question, I would seriously consider putting the surge protector in front of the UPS and protect the whole system. > > We must also consider the power availability angle. > > If the surge protector is in front of the UPS; then even if the surge protector sacrifices itself; or blows a fuse to protect the UPS from the surge; the UPS will still power all of the equipment attached to it from its battery. > > If the surge suppressor were after the UPS; then blowing a fuse or tripping the surge suppressor would prevent the UPS from powering its outputs. > > Chris Maxwell | Design Engineer - Optical Division > email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 > > NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA > web www.nettest.com | tel +1 315 797 4449 | This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Surge Suppressors on a UPS
I disagree. One assumes some degree of surge suppression since suppression is touted as a UPS feature. Therefore your question is moot. Fred Townsend Chris Maxwell wrote: > To me, this whole thread begs the question: Why not put the surge supressor in front of the UPS? > > Chris Maxwell | Design Engineer - Optical Division > email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 > > NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA > web www.nettest.com | tel +1 315 797 4449 | > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Bad Fuse vs. Good Fuse
Dan I agree in general with your comments. I will go so far as to stipulate many design engineers don't know their hole from an ass in the ground as far as properly specifying fuses. That being said the fuse industry has a problem. I have seen many, genuinely defective fuses. I have seen even more genuinely defective fuse holders that make the fuse appear defective. Fuse holders that were so hot they melted the fuse because they had several ohms of contact resistance caused by the holder manufacture not properly cleaning them. I am happy to state that 99.5% of the problems I have seen were not with Buss fuses. The vast majority of problems lie with your competitors that undersell Buss. Purchasing thinks a fuse is a fuse is a fuse and buys the cheaper fuse. How about some guaranteed AQL levels that the engineers can specify to keep the bad guys out of the purchasing office? Is there an IEEE group for fuses? Maybe there should be. Fred Townsend "Giblin, Dan" wrote: As a fuse manufacturer, I have read all the e-mail on this subject with great interest. Unfortunately, many responses emphasize common misunderstandings. In the fuse industry, there is no such thing as a "Bad" fuse. The chain of e-mails clearly indicate why we avoid this word due to its various meanings. Similarly, we try to avoid the word 'failure'. A "bad" or 'failed' fuse can mean any number of things, but the most common is that the fuse is open, (it operated). Thus, the fuse did what it was supposed to do - operate - and yet it is deemed 'bad' or a 'failure'. There are numerous occasions when a customer returns a 'bad' fuse. The fuse was 'bad' because it operated properly. In many instances, the choice of fuse type or amperage rating was flawed. For being such a 'simple' device, there are many items that influence the correct choice. I will address some of these by picking quotes out of the various e-mail on the subject. Among these are: * Voltage rating - (This was addressed in Mr. Richmond's e-mail - I've heard of a "bad" fuse, in this case, a fuse not adequate to protect the circuit and user. A 30 volt fuse can't be counted on to interrupt a 408 volt circuit. This is absolutely correct. Choosing a voltage rating below your application can be very dangerous. * Continuous Current rating - This was addressed in Mr. Beckwith's e-mail - Fuse operation when there is no fault can also sometimes be caused by incorrect specification at the design stage, i.e. the fuse is rated too low for the actual current consumed. Very true. One must look at surges mentioned below and temperature. * Temporary Surges that you want the fuse to pass - A time delay fuse is typically chosen for motor or transformer applications. This is addressed a little in Mr. Beckwith's e-mail - We have all seen cases where a fuse blows when there is no apparent fault in the equipment, hence the maintainer's comment "bad fuse". In my experience, this is usually caused by a temporary overload condition or a power surge, not a "bad" fuse. * Temporary Surges that you do not want the fuse to pass. * Ambient temperature rating - This was addressed in Mr. Hughes e-mail below. * Interrupting Rating - This was addressed in Mr. Hughes e-mail - A couple of other common design drop-offs I would like to mention include failure to select a fuse with an adequate prospective fault current (i.e. selecting a 5x20 mm glass fuse - rated at Isc=35A max and using it in a mains circuit where the prospective fault is in the order of 1kA) and 'forgetting' to de-rate the fuse for use in a high ambient temperature (although this has already be mentioned re. pico-fuses). * Shock/Vibration - Most fuses do not claim to be suitable for such applications. From Mr. Schlentz - I have seen one instance where a fuse opened during a vibration test. I think that was a BAD FUSE. I don't know if the fuse in question was supposed to be suitable or not. If chosen incorrectly, and 'nuisance' opening occurs, as Mr. Powell mentions - Often the answer is, increase the fuse size to prevent nuisance trips. The risk, of course, is that for every incremental increase in fuse value, you increase the risk of fire proportionally. In doing this, you may be defeating the purpose of having the protection there in the first place. If a fuse nuisance opens, it is likely that one of the above bulleted items was overlooked. Additionally, as Mr. Richmond points out - Many fuses ARE mechanically fragile; it's simple physics that says a low-current fuse will be a fragile thread. Think of them as light bulbs. We do not call a light bulb unreliable if it fails after being dropped on the floor; we call it broken. This is particularly true for
Re: Bad Fuse vs. Good Fuse
Doug when I ran my own section of a factory I forbad my testers from using the term "bad" or its military equivalent "NFG" on their failure tags although we saw the term many times on field returns. Bad isn't descriptive. Instead they were instructed to simply describe why they thought the unit was defective. This sounds complicated at first, but we quickly worked out some simple codes. i.e. ma=0 meant the unit didn't draw any current. If ma=0 then it was quite possible the fuse was open but the fuse was not the defect, rather a pointer to a latent defect. On the other side fuses and fuse holders were probably the least reliable components we had with defect rates of 4 to 80%. Sometimes it was very confusing. A fuse that had opened because the current exceeded rating was not defective but merely a formally functional open fuse. Then again a fuse that was open before any current was passed was definitely a defective fuse. 125 or 180 ma fuses could be made defective merely by dropping them. We had some signaling fuses that would blow on over current but fail to signal. These were defective blown fuses. I fear I may have added to the "fog" but at least I never used the term "bad". Fred Townsend "POWELL, DOUG" wrote: Hello all,Recently, in my company, we've been discussing what exactly constitutes a good or bad fuse. In this industry we often hear that the trouble with a defective product was, "the fuse was bad." I occurred to me that the fuse is not bad, it performed exactly intended. In fact if the problem that caused the fuse to "operate" is still present, then the fuse is still good even though it is now an open circuit. The only time it can be a bad fuse is if it did not operate, resulting in shock or a fire.I have now have my ears tuned-in to this concept of a "bad fuse" and find it is commonly used all over the industry. In fact you can go to any number of websites that provide trouble shooting notes, and find instructions on how you can measure a bad fuse from a good fuse using an Ohm meter, photos included. And some of these instructions are from reputable manufacturers. Another term often used is "defective fuse", which in some way sounds more scientific, but is still fundamentally wrong.I recently saw a newspaper article that gave the explaination why electrical service was lost for over 100,000 people as a bad fuse. An investigation was under way to determine why the fuse went bad. This is a little like hearing the technologically uninitiated say "it must be a short somewhere", when the television set stops working.Maybe I am finicky, but this affects how companies view real product defects. When the "defect" is the bad fuse, then the real problem may be covered up. Often the answer is, increase the fuse size to prevent nuisance trips. The risk, of course, is that for every incremental increase in fuse value, you increase the risk of fire proportionally.Any thoughts or experiences?BTW - To all US citizens in the group, have a relaxing Memorial Day weekend.-doug Douglas E. Powell Regulatory Compliance Engineer Advanced Energy Industries, Inc. Fort Collins, CO 80535 USA ___ This message, including any attachments, may contain information that is confidential and proprietary information of Advanced Energy Industries, Inc. The dissemination, distribution, use or copying of this message or any of its attachments is strictly prohibited without the express written consent of Advanced Energy Industries, Inc.
Re: Heat Sink Colour.
Scott I would disagree on several points: My recall of heat transfer says that forced convection (i.e. high velocity forced air cooling) that turbulent air is roughly twice as effective at cooling as laminar flow air. Therefore a rough finish or ribbed finish would be used. For natural convection smooth finish would aid laminar flow and therefore be desirable. (Turbulent air flow is not normally achieved without a forcing function.) Just backwards of what you indicated. As for color, convective heat sinks will still achieve some radiated heat loss, particularly at higher temperatures. Therefore the heat sink should have an emistivity as close to one as possible. This is best achieved with a "black body", not polished aluminum. Fred Townsend Scott Lacey wrote: > As a general rule of thumb, use polished aluminum fins (no finish) > for high velocity forced air cooling (maximum thermal transfer to the > airstream). > > Black anodized works well with more gentle airflow, and you would > want a rough cast or sandblasted blackened finish when relying > solely on natural convection. The rough surface increases both > surface area and turbulence. > > scott Lacey > > > On 9 May 2003 at 9:50, LEUNG YAT WAH DEREK wrote: > > > > > > > > > Could anyone tell me about the heatsink is really in lighter colour > > can release heat faster ( similar to we wearing lighter clothes in > > summer), but why people always painted the heatsink in black or very > > dark colour, and the material of the coating on heatsink will affect > > their performance? Thanks. > > > > > > > > --- > > This message is from the IEEE EMC Society Product Safety > > Technical Committee emc-pstc discussion list. > > > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > > > To cancel your subscription, send mail to: > > majord...@ieee.org > > with the single line: > > unsubscribe emc-pstc > > > > For help, send mail to the list administrators: > > Ron Pickard: emc-p...@hypercom.com > > Dave Heald: davehe...@attbi.com > > > > For policy questions, send mail to: > > Richard Nute: ri...@ieee.org > > Jim Bacher: j.bac...@ieee.org > > > > Archive is being moved, we will announce when it is back on-line. All > > emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Radius High Speed Lines
The article at: http://www.ultracad.com/90deg.pdf deals with your question. Although he specifically deals with 90 degree corners, 45 degree are addressed too. Fred Townsend This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Heat Sink Colour.
Very simply, dark colors pass radiated energy. Light colors reflect radiated energy. The human body radiates very little energy but the sun contains huge amounts of radiated energy. Therefore white clothes are cooler because they reflect the sun's energy. Fred Townsend LEUNG YAT WAH DEREK wrote: > Could anyone tell me about the heatsink is really in lighter colour can release heat faster ( similar to we wearing lighter clothes in summer), but why people always painted the heatsink in black or very dark colour, and the material of the coating on heatsink will affect their performance? Thanks. > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Heat sink thermal impedance.
I'll take a guess at the terms. I suspect the term thermal impedance may be misapplied. There is a rather lose parallel. Electrical resistance is a scalar quantity. Electrical impedance is a vector quantity. In a strict sense the impedance to heat transfer is a 3D quantity that can be represented by a surface integral. Any portion of that quantity could be represented as a vector quantity. In another sense thermal analysis would deal with the total thermal impedance. A heat sink would normally be specified for thermal resistance. Fred Townsend LEUNG YAT WAH DEREK wrote: Who can tell me what is the difference between "thermal impedance" and "thermal resistance" when talk about heat sink, thanks. Derek Leung.
Re: ESD failure
By process of elimination the failure you describe could be caused by either ground bounce or induced current. In this case the negative polarity rules out ground bounce so you are looking for an induced current path. This is probably some lightly loaded input. Since you say that some ASICs work and other don't I would suspect your ASIC designer or fab has left out the Schottky diodes in the bond pads. This could be confirmed by temporarily installing small Schottky diodes on all ASIC inputs. The permanent fix would be to get the ASIC properly designed. It is predictable that adding capacitors to the power supply would not effect the problem since I presume the power supply leads are already decoupled. Fred Townsend Ravinder Ajmani wrote: > Hi ESD Gurus, > I am having problem with a controller card which is failing contact ESD > discharge at Negative 5 kV and below, but passes Positive contact discharge > upto 8 kV, and air discharge of either polarity upto 15 kV. The card is > mounted on an open metal chassis, and has DC input of 5V and 12V coming > from a power supply. The ground of the card is directly tied to the > chassis at several places. I am not discharging into the controller > chassis, but l place the unit on my ESD table and discharge into the > horizontal coupling plane, which results in the failure. > > Through my testing, I have isolated the problem to the main ASIC on the > card. An earlier version of the same card passes the test, whose ASIC is > built from the same CMOS process, but has a different processor core. It > is difficult to determine which part of the ASIC logic is latching up. I > have tried adding low value decoupling capacitors to power supply, but it > has no effect on the problem. > > Any suggestions on what I should I try next. > > Regards, Ravinder > Server PCB and Flex Development > Hitachi Global Storage Technologies > > *** > Always do right. This will gratify some people and astonish the rest. > Mark Twain > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Racing Car EMC
Ed, the ignition systems on race cars are formidable EMI sources. Furthermore racers tend to disdain of EMI suppression. I have heard many of a mechanic say with reference to stock cars, the first thing they do is to soap one up is "Rip out all that suppresser crap" (meaning EMI suppression). Fiberglass bodies such as used on the Corvette are very difficult to quite down because of the lack of a good frame ground and shielding. As for standard I don't have a political recommendation but from a operational standpoint I would recommend aviation standards. Fred Townsend "Price, Ed" wrote: > >-Original Message- > >From: Peter Conboy [mailto:peter.con...@piresearch.co.uk] > >Sent: Monday, March 17, 2003 1:50 AM > >To: 'emc-p...@majordomo.ieee.org' > >Subject: Racing Car EMC > > > > > > > >Anyone out there got an opinion on what standards should be > >applied for the > >electronics fitted to racing cars - F1, CART, IRL etc.? > > > >Because of the environment, the need for absolute reliability, and the > >safety critical application (e.g. throttle, clutch, steering, chassis > >control) we take things seriously, but do not actually "CE" or > >"e" mark. The > >tests I do generally cover "e" and exceed most standards as > >actually I try > >and "break" the box rather than just go to the standards limit. > > > >I am having a bit of a debate inside my company, because > >95/54/EC refers to > >only vehicles on rhe road, and racing cars are "off road" and therfore > >implies "CE" as a catch all This to me is wrong as patently > >its a vehicle, > >"CE" may be broader on the immunities, but is less severe on > >the radiated > >stuff. Given the self contained nature of the car, it is the radiated > >immunities I feel I should be most concerned with once I'm sure engine > >sourced interferences have been dealt with. > > > >Also CE and "e" are EU, whats the legal U.S. position? - I > >stress legal > >because the teams themselves don't care. > > > >Thanks > > > >Peter > > > > Peter: > > What kind of an RF environment does a race car experience? There's an audio > link to the driver, a telemetry link for structural data, and possibly a > video link for a car camera. And then all the similar links for the other > cars. Does the car see any special exposures on the course (Doppler radar?) > or in the pits (noisy service tools)? And, are there any unusual operational > conditions, like running without a battery (saves weight, more ripple) or > operation of heavy actuators or solenoids? > > Regards, > > Ed > > Ed Price > ed.pr...@cubic.com > Electromagnetic Compatibility Lab > Cubic Defense Systems > San Diego, CA USA > 858-505-2780 (Voice) > 858-505-1583 (Fax) > Military & Avionics EMC Is Our Specialty > Shake-Bake-Shock - Metrology - Reliability Analysis > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Swissair 111 error in reporting
You caught the error. For those who didn't here is an explanation. Notice how the error effects perception. Here is the text clip: ...heat generated by the system made the hard drives hot enough to fail. Aboard an airplane, the hard drives would probably get 10-20 degrees Celsius (50 to 68 degrees Fahrenheit) hotter than in a laboratory, he said. The reference here is to temperature rise, not absolute temperature. No doubt the author didn't know the difference and when he added the conversion in parentheses used a conversion table instead of a conversion factor. It should read (18 to 36 degrees Fahrenheit). The significance is 36 degrees F (rise) is within the manufactures limits but 68 degrees F (rise) is probably not. Putting it in terms that are a little easier to understand using the manufacture's data sheet to calculate maximum ambient temperature for the quoted rises, the cabin temp must be maintained at 63 F as the author wrote it. The correct maximum is 95F. I think the author has significantly distorted the perspective unless you never pay attention to temperature in Fahrenheit degrees. Fred Townsend "Price, Ed" wrote: Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis >-----Original Message- >From: Fred Townsend [ mailto:f...@poasana.com] >Sent: Wednesday, February 19, 2003 12:42 AM >To: Ken Javor >Cc: Gary McInturff; EMC-PSTC (E-mail) >Subject: Re: Swissair 111 - long winded even by my standards but an >interesting article > > > >Scary! I squirmed in my seat as I read the article. You see I did the >electrical design part of a similar system. Our system had a >critical design >flaw. It was a mechanical error so I was not responsible for >the error but it >could have crashed the airplane. Luckily we did not use a >contractor for >certification. We submitted straight to the FAA. The FAA >spotted the problem >and it was soon fixed. It makes me wonder what would have >happened if we used a >contractor to certify. > >In another vein, did anyone else pick up the error in the >article? It related to >the disk drive. It probably was the reporter's error. I see >errors of this >kind so frequently when you have a journalist or English major >writing about >scientific issues. They are not equipped to do the job. > >Fred Townsend Do you mean: "Aboard an airplane, the hard drives would probably get 10-20 degrees Celsius (50 to 68 degrees Fahrenheit) hotter than in a laboratory, he said." I just assumed that it was the reporter having a problem with arithmetic. I was more interested in the comment that the heat rise "observed in the laboratory" would probably have been even hotter in a real installation. So why didn't they get a typical seat, stick it in an altitude chamber, and find out what the heat rise really was? I'm not very familiar with the certification process for adding a gadget to an aircraft. But, it seems to me that the aircraft modifiers, like SBA, are supposed to use only accepted or certified parts in the modification. It seems like there's a gap, from the time that the manufacturer's first FAA consultant bailed out of the job, and the time when SBA started installing the systems onto aircraft. I didn't see anywhere in the story that the entertainment systems were ever "certified" or whatever they call it, to be used by anyone. Ed Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis
Re: Swissair 111 - long winded even by my standards but an interesting article
Scary! I squirmed in my seat as I read the article. You see I did the electrical design part of a similar system. Our system had a critical design flaw. It was a mechanical error so I was not responsible for the error but it could have crashed the airplane. Luckily we did not use a contractor for certification. We submitted straight to the FAA. The FAA spotted the problem and it was soon fixed. It makes me wonder what would have happened if we used a contractor to certify. In another vein, did anyone else pick up the error in the article? It related to the disk drive. It probably was the reporter's error. I see errors of this kind so frequently when you have a journalist or English major writing about scientific issues. They are not equipped to do the job. Fred Townsend Ken Javor wrote: > I drove from Huntsville, AL to Ft. Wayne, IN, today mostly because flying > is such a pain these days. Now I'm glad I drove from a safety viewpoint as > well. > > Seriously, there is something wrong if gov't oversight is necessary to make > sure an aircraft is put together right. I think there is a very simple, > very old fix for this problem. Accountability. They had it back in > Babylon. The Code of Hammurabi. If an architect builds a house, and that > house collapses and kills the owner, then the architect's life is also > forfeit... > > on 2/18/03 7:50 PM, Gary McInturff at gary.mcintu...@worldwidepackets.com > wrote: > > > > > http://www.usatoday.com/travel/news/2003/2003-02-17-swissair.htm > > > > > > > > > > --- > > This message is from the IEEE EMC Society Product Safety > > Technical Committee emc-pstc discussion list. > > > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > > > To cancel your subscription, send mail to: > > majord...@ieee.org > > with the single line: > > unsubscribe emc-pstc > > > > For help, send mail to the list administrators: > > Ron Pickard: emc-p...@hypercom.com > > Dave Heald: davehe...@attbi.com > > > > For policy questions, send mail to: > > Richard Nute: ri...@ieee.org > > Jim Bacher: j.bac...@ieee.org > > > > Archive is being moved, we will announce when it is back on-line. > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc > > > > -- > > Ken Javor > EMC Compliance > Huntsville, Alabama > 256/650-5261 > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: best screw/washer choices for attaching PCB to Chassis?
Kim, you ask some interesting and well thought out questions. I'm sure you will get a lot of diverse opinions. You have entered into the domain of system grounding. System grounding may be governed by a number of codes, such as NEC, UL, and CSE for the North American continent. A lot more for the rest of the world. More importantly the ground system will impinge on the signal integrity of the PCB circuit. Hopefully the circuit designer has already addressed these issues although, from your question I suspect he/she hasn't fully addressed them. Let me tell you what has worked for me. Kim Flint wrote: > Hi- > > We have a fairly straightforward requirement of mounting a PCB into a steel chassis. The chassis has PEM type standoffs and the PCB is held to them with machine screws. These connections provide an electrical ground path between the PCB and the chassis. > > In other words, we have what seems to be the fairly ordinary and common set of requirements. We need to have mechanical reliability (so the PCB is held in place), nothing should break during assembly, the screws should not be able to work themselves out, and electrical conductivity should be low for a low impedance ground path. Seems simple, yet all of us here have a different opinion about how to do this properly, we've all done it a variety of ways in our past, and none of us seems to have the right expertise to really claim to know the definitive answer. > > I'm hoping to get some expert opinions from this group, or at least some idea of what others do assuming there is some reasonable justification for it. Can you help? Or perhaps point me towards some good discussion on the subject? (I did search the 2+ years of mail I have from this group, since the archives don't seem to be online...) > > The questions are: > > Screw/Washer choice: > - should a washer be used or not? > - if a washer is used, should it be a locking washer? > - Is it possible for a locking washer to cause unwanted damage to the PCB? > - Is an adhesive like Loctite a reasonable alternative to lock washers in this case? > - should the screw be zinc plated? or some other plating? > IPC (www.ipc.org) has many documents that will clarify your questions. Washers are always a good idea but may be made part of the PCB, the screw or as a separate part. Split locks may be used on top of flat washers. If split locks are used directly against the PCB it will tend to gouge or craze the PCB gel coat. Loctite, preferably blue can be used but I do not recommend it unless there is no way to use a lock washer. It is more expensive, hard to QC, and generally a pain to use. It also increases the ground resistance in some instances and may represent a latent defect. Loctite is also dependent on the type of plating used. I use stainless steel, binding head or washer head screws for normal applications. I use nickel plated brass screws with internal tooth star lock washers for high current applications. > > PCB layout: > - Should we use a plated through-hole with ground planes connected inside the hole? > - or a non-plated hole with vias in the surface layer pad connecting to the ground plane? > - What electrical or reliability concerns relate to this choice? > - how large should the surface pad be assuming a 4-40 screw? > > anything else we should be considering? > Again, we are dealing with the system ground circuit design which will dictate whether the mounting holes are grounded or not. My preference is for unplated and ungrounded. Wherever possible I like to use mounting holes for tooling holes. This is easy to do if unplated. It also saves a manufacturing step since unplated holes don't have to be plugged for wave soldering. I like to use as big a pad as possible, somewhere between .150" and .180" since big pads are great for automatic screw drivers and such. In no way should the system ground be floated. By using an unplated hole it is assumed there is a system ground through a connector or other scheme. If there is no other ground, then by all means use a plated hole to connect as necessary. Finally, don't forget to an ESD (Electrostatic Discharge) analysis. You may find ESD avoidance driving your overall grounding plan. Fred Townsend > > Thanks for any input you have! > > kim > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For poli
Re: Maintaining conductivity of freshly machined aluminum
Check out Alodyne. It's a machine shop process like anodize but conductive. Fred Townsend Scott Lacey wrote: > To the group, > > Does anyone know of any conductive coating, preferably spray-on, > that could be used on mating aluminum chassis surfaces? We > manufacture (in very low volume) test equipment that is housed in a > commercially manufactured anodized aluminum enclosure. Our > machine shop mills the anodizing from mating surfaces and adds > additional screw holes to improve bonding. The concern is that the > surfaces will not remain conductive over time. > > Conventional dip alodyne is out of the question. The process would > mar the black anodized finish on the exposed portions. We are > considering using a wipe-on alodyne that Dupont sells to the > autobody trade but have concerns as to its suitability for this > application. > > The ideal would be a spray-on conductive coating that we could > apply to the exposed aluminum after masking the anodized parts. > We would abrade the surfaces with fine Scotch Brite just pryor to > painting. Does anyone know of such a product? > > Scott Lacey > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: BeCu problem
John, tubes are like vacuum deposition chambers. I have difficulty believing that a fancy form of carbon would be of any use in molded structures, HV, or HVAC. These conditions are all found in radar tubes. Also, thanks to Greggs comment about fancy screw drivers, I remembered that BeCu screw drivers, wrenches, etc. are used by the military in explosive environments because of their no sparking characteristics. Fred Townsend John Woodgate wrote: > I read in !emc-pstc that Fred Townsend wrote (in > <3e3a35fb.6ecc...@poasana.com>) about 'BeCu problem' on Fri, 31 Jan > 2003: > >BeO has seven times better thermal conductivity than AlO (alumina). There is > >no real substitute for BeO at high power levels. It is still used by the > >Military in high power radar applications such as tubes. > > Vapour Phase Deposition of diamond may replace BeO, with improved > thermal properties, AIUI, and no toxicity problem. > -- > Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk > Interested in professional sound reinforcement and distribution? Then go to > http://www.isce.org.uk > PLEASE do NOT copy news posts to me by E-MAIL! > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: BeCu problem
I can't help you with the regulations but I can clarify the usage of Beryllium a bit. When Beryllium is added to copper it makes it very hard. It is used in gaskets to make them springy. Stainless steel is a poor substitute because it lacks both the electrical and thermal conductivity. So far as I know there is no handling hazard unless you saw or grind it. Beryllium oxide BeO has similar restrictions on grinding. I don't know if it can be sawed. It would probably take a diamond blade in a liquid bath to have a chance at sawing. BeO has seven times better thermal conductivity than AlO (alumina). There is no real substitute for BeO at high power levels. It is still used by the Military in high power radar applications such as tubes. Fred Townsend Jan Vercammen wrote: > Hello EMC/PSTC-list, > > I have a question concerning Berylium Copper (BeCu). Even though this is > not a direct > EMC oriented question, it is or could be, indirectly, a serious problem in > the EMC shielding of our > products. > > I have been asked if BeCu can still be used in Europe and the USA (and the > rest-of-the world) as > the material for shielding gaskets and fingers. > > The main issue here is that Berylium (probably in combination) is > classified as an carcinogen and > it is also know to cause lung diseases (e.g. CDB or chronic Berylium > disease). Note that this is only the > case if small particles are inhaled into the lungs. However, I have also > received conflicting information > that it is BeO (Berylium Oxide) which is or could be the cultprit. BeO is > used as an electronic packaging material. > > Therefore I assume that the BeCu gaskets and fingers are not an health > hazard when used as a > shielding part in our products, but are (or could be) hazardeous during > manufacturing and recycling. > > I have been told on several occasions that BeCu is not allowed any more, > but one can not provide > me with standards or legal texts to substantiate the above statements. I > have also been told that > we need to change the BeCu shielding parts asap to stainless steel parts. > However, personally > I do not feel convinced and was hoping that EMC experts on the > EMC/PSTC-list could help me out with the > following questions: > > -1- is it correct that BeCu fingers/gaskets are considered a hazardeous > substance and that they will > be abolished from electronic equipment? > -2- if question 1 is correct, what is then the exact argument for not > using BeCu?? > -3- are there (world wide) legal standards/regulations published that state > that BeCu (as a finished product) > cannot be used anymore and by which date??? > -4- what is your experience with the conversion of BeCu to stailess steel > gaskets/fingers for non-dynamical > shielding applications (cost, problems, ...)??? > > Kind regards, > > Jan Vercammen > Agfa-Gevaert NV > Mortsel, Belgium > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: AV terminations... dropping the other shoe
With 1 K sources you would leave them unterminated. Fred Townsend John Woodgate wrote: > I read in !emc-pstc that Dan Pierce wrote (in > <77181e93ba2ad41187650090279c18a002c00...@exchsrvr1.indy.escient.com>) > about 'AV terminations' on Wed, 11 Dec 2002: > >I was wondering what the typical load termination to use for audio and video > >RCA connections on a typical receiver, both in and out. > > Sources are 1 kohm to 2 kohm, inputs are 10 k to 22 k. > -- > Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk > Interested in professional sound reinforcement and distribution? Then go to > http://www.isce.org.uk > PLEASE do NOT copy news posts to me by E-MAIL! > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: High Speed Clock Routing
It is difficult to generalize without knowing more of the specifics such as logic family, clock rate, edge rate, trace impedance, etc. but I'll try. ;) scott@jci.com wrote: > All, > > I have a question regarding trace routing for high-speed clock signals. > > I have one driver, and two receivers. The distance between the driver and > 1st receiver is roughly 2.5cm, the distance between 1st receiver and 2nd > receiver is 3cm, and the distance between driver and 2nd receiver is 3.5cm. > > I actually have 2 questions: > > 1) What is a good rule of thumb for routing and termination of this > high-speed clock trace? Do it carefully. Sorry to be so obtuse but without knowing what the "speed" is in "high-speed" I don't know what else to say. > > 2) Is daisy chain routing preferred (meaning driver to 1st receiver, > then 2nd receiver), or should 2 traces of equal length be routed, 1 to each > receiver (each of these two traces will have twice the impedance of the > single trace emanating from the driver so that impedance matching will be > maintained)? Daisy chaining is to be avoided since it increases clock skew but it is much simpler to drive and terminate. Termination reduces reflections but leads to higher static and dynamic current flow. EMI is related to current flow so it is possible to increase EMI by terminating. Double the traces and you more than double the termination problems. There are partial solutions such as partial termination and diode clamping techniques such as "Forced perfect" but none are simple. This is why SI Engineers make good money. For your geometry your 2t reflection on a daisy chain would occur around 300 ps. This is probably acceptable unless you have some sub nanosecond logic in your circuit. Ok to generalize, you don't need to daisy chain if the total path is not over say 5 cm in length. (This assumes you are not running sub nanosecond or TTL logic.) You can probably get by without terminating or by partially terminating in say 200 ohms. Fred Townsend DC to Light Consulting > > > Any information, in general, or in specific on the subject is greatly > appreciated. > > Thank you. > > Best Regards, > > Scott Mee > Johnson Controls Inc. > Automotive Systems Group > EMC Product Compliance > > 616.394.2565 > scott@jci.com > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: Ground Fill on Multi-Layer PCBs
Darrell, one can only guess whether it is necessary to fill unused ground area. You haven't supplied enough information to tell. If the ground is a reference ground plane for establishing impedance anywhere then you must fill the plane. If thermal considerations exist then fill it. If current considerations exist then fill it. It's hard to make a case for not filling. To consider this trade-off at all makes me wonder how hard it is to do the "extra work". Ground fill is a simple thing to do in most modern CAD systems and would be an automatic for me unless I had some excess capacitance in a circuit to worry about. Fred Townsend Darrell Locke wrote: > Group, > > On two layer boards its always good to fill unused area with ground (signal > return) for tight coupling. What about a six layer board with high speed > traces sandwiched between two ground/power planes. Should the layer with > only signals have ground fill? I don't think it would hurt EMC performance, > but is the gain in decoupling worth the extra work? Anyone have expereince > with this or know of technical papers on the subject? > > Thanks > > Darrell Locke > Advanced Input Devices > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: Lightning Protection for PA System
Scott it sounds like you have a tiger by the tail in that you are in a particularly hot lightning location. Your efforts to date sound reasonable. I will expand on a few statements. First, your system is a good deal like a telephone system and many of the techniques used in telephony may help you. You might like to check out the US Printing office for REA documents relating to lightning protection. For the 70 volt outputs I am thinking of using gas tubes to earth where the wires enter the building supplemented by MOV, Tranzorb, or other devices near the amplifier location. I welcome suggestions as to device types. Tranzorbs are a very good product. They also come in a wide range of voltages which make them applicable to almost all applications. They are fastest devices available and the only ones that stand a chance of reacting to the leading edge of the current pulse. MOVs are the heavy lifters but are generally too slow to offer much leading edge lightning protection. They are labeled transient protectors as opposed to lightning protectors for this reason. Gas protectors fall in the middle for speed and are only available for higher voltages. All of these devices will fail in time if subjected to repeated lightning strikes. Diodes (Tranzorbs) fail shorted. Gas tubes fail open. MOVs may fail open or low resistance. Ordinary silicon signal diodes can be used to protect microphone inputs. Fast shockly power diodes can be used too. Remember the bigger the diode the slower it reacts. All of the above components are network devices meaning they are not designed to absorb the total energy of the lightning strike by themselves. They are designed to work in conjunction with other components in the protection network. The protection components, particularly diodes, need to react with some resistance or inductance to limit current. The copper resistance of the wire and transformers may be enough but adding a few ohms more, say 4.7 ohms, 1 or 2 watts, in series with each side of the line, will usually allow the diodes to survive a direct hit. Inductors and inductive resistors (wire wound) sound like a neat idea since inductance will slow down the wave front and provide an impedance for the protection devices to react with. In reality inductors do not survive well. This is because magnetostrictive reaction, particularly in solenoid wound resistor or inductors, can explosively shatter the coil form. However, I have seen dual segment wound, toridal, common mode chokes successfully used. The ferrite cores do not shatter. Good luck, Fred Townsend Scott Lacey wrote: > To the group, > > I am seeking advice as to the best methods of protecting a Public Address > system > against recurring lightning damage. The system uses several commercial PA > amplifiers, each driving several speakers at indoor and outdoor locations. > There are > also several locations where microphones can be plugged in. The longest > speaker > wires may be up to 250 yards long. It is believed that the charge is being > coupled to > the speaker wires where it then returns to ground at the amplifier location > within the > building, destroying the solid state devices within the amplifier. A > technician has > added fuses to all external microphone inputs and speaker outputs. While these > have blown several times during storms without obvious damage to the > amplifiers it > is my belief that fuses are generally too slow to protect semiconductor > devices. I am > seeking advice as to surge suppression devices. > System particulars are as follows: > > 1) The PA amplifiers have 70 volt outputs. All speakers are transformer > coupled. > > 2) All microphones use standard XLR connectors. They plug into metallic > conduit > mounted jacks at locations inside and outside the building. The outside > microphones > are unplugged during storms. > > 3) The amplifiers are located on the second floor of the building. Each > amplifier is > dedicated to a set of speakers at one location. The amplifier driving the > longest wires > is the one which most often has to be replaced. > > 4) The building is in a location known to be susceptible to lightning > activity. Electrical > appliances have been destroyed on at least two occasions. > > 5) All protective grounding efforts to date have been made to the conduit. I > am > recommending that this be supplemented by driven rods. > > It is pretty easy to buy commercial surge suppression devices for the ac > lines. I feel I > need advice as to the best methods to protect the audio inputs and outputs. > > For the 70 volt outputs I am thinking of using gas tubes to earth where the > wires > enter the building supplemented by MOV, Tranzorb, or other devices near the > amplifier location. I welcome su
Re: An ESD question
It is interesting to see how easy it is to lose focus. The problem is not the humidity, approach speed, etc. as Richard has suggested. Yes, they are factors but not the problem. The problem is a massive design flaw. 800 volts is way too low. The fact there are multiple failure modes supports the conclusion something major is wrong. The designers needs to review their ESD suppression and grounding of this product. You may need to call in an ESD or SI expert. This product is not ready for prime time. This discussion would be relevant if we were trying to sneak through a product that passed at 4 KV but failed at 5 KV but not at 0.8KV. Fred Townsend Chris Maxwell wrote: > Vic, > > I agree, your product is probably seeing field failures because of the dry > conditions. These dry conditions make the probability of an ESD event > higher. This is due to the fact that, as personnel walk across carpets or > rub their clothing on chairs, there is no humidity in the air to help bleed > and equalize charge. So, they have a higher probability of charging up and a > higher probability of discharging to your equipment. (You probably already > know this.) > > Of course, your problems may not be due to people discharging to your > equipment. It could be due to some other source of ESD. It could be a > discharge from a nearby object. However, the same argument holds. The dry > atmosphere increases the probability. (Hence the static cling present in > clothes that come out of a dryer.) > > So, in both cases, you are probably seeing more failures in a dry atmosphere > because the probability of an ESD event is higher. Higher failure rates in > dry atmospheres are due to this probability increase. The higher failure > rate is probably not due to a dry atmosphere ESD event being different from a > humid atmosphere ESD event. > > For testing, you are already generating the ESD event with a simulator. The > ESD generator takes probability out of the equation. You can generate a > discharge whenever you want. So, in my humble opinion you don't need to > simulate the dry conditions. I would simply follow IEC 1000-4-2, which > recommends test conditions with a humidity level between 30% and 60%. With > this combination of ESD generator and humidity, you should get a discharge > whenever you want; and it should couple to the victim in proper fashion. > > I agree that you will see different performance at different levels. I have > seen failures at 4KV air discharge that are not repeatable with 8KV air > discharge. So it is worth the time to test at lower levels until you get up > to the compliance level that you are shooting for. > > Chris Maxwell | Design Engineer - Optical Division > email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 > > NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA > web www.nettest.com | tel +1 315 797 4449 | > > > -Original Message- > > From: Gibling, Vic [SMTP:vic.gibl...@marconi.com] > > Sent: Wednesday, June 12, 2002 3:26 AM > > To: emc-p...@majordomo.ieee.org > > Subject: An ESD question > > > > > > > > Dear Group > > > > I tried to find David Pommerenke article's in the Journal of ESD on the Web > > but alas no downloadable version was found, so may I ask the group a > > question? > > > > We have an ESD field failure which is occurring in dry hot countries ( no > > surprise )which can be recreated with an ESD of -800V. In an attempt to get > > a high incidence of discharges we used a dehumidifier to create a dry > > environment. The result was a reduction in discharges. > > > > Thinking the problem through -now- as a dry atmosphere will encourage the > > production of high level ESD and a humid environment inhibits the charge to > > a lesser level, presumably because it 'leaks' away. Then is it wrong for us > > to attempt to 'dry' the local atmosphere in the hope of gaining consistent > > ESD from an ESD gun, that is to say the more humid the environment the more > > efficiently the discharge will transfer to the victim? > > > > Incidentally, to add to the thread regarding intermediate level testing for > > ESD and EFT. This exercise has revealed different failure mechanisms at > > different ESD levels. > > > > Your views would be appreciated. > > > > Vic Gibling > > Compliance Engineer > > Marconi Applied Technologies > > > > > > > > --- > > This message is from the IEEE EMC Society Product Safety > > Technical Committee emc-pstc discussion list. > > > >
Re: DOC "Assembled from tested components"
Rocky: It is not clear what information you are looking for. Are you looking for hook-up information or trying to write a driver? If you want to know how to hook it up, both Sony and Teac have such documents. If you are writing a driver, the data sheet on the old NEC 765 controller chip may be of some help. No one uses the 765 any more because they use multifunction chips but the data sheet is still the most comprehensive for the driver writer. Fred Townsend "Gonzalez, Kenneth P (Rocky)" wrote: > All, > Has anyone successfully issued a DOC using the "assembled from tested > components" method for a personal computer? I have not been able to find a > floppy disk drive manufacturer that has any DOC documentation for their > device; even the ones marketing directly to home users. Have I just not > found the right manufacturer? > > Best regards, > > Rocky > -)-(- > > Kenneth P. Gonzalez (Rocky) > Intergraph Solutions Group > Integrated Products Division > 170 Graphics Drive > Madison, Alabama, USA 35758 > phone (256) 730-2131 > fax (256)730-2424 > kpgon...@ingr.com > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: stun guns on aircraft
Peter: Let me answer your questions and then I have a question for you. "FLOWERDEW, Peter" wrote: > > > I am reading this thread in the UK. I am a trained marksman, trained > by our police, but I can not believe what I am reading. How many > murders per day in New York? Unless you count the murders at the World Trade center where there were no guns involved, about 200 per year. How does that compare with London? > How many in any European capital? > How many school massacres in USA? Per capita about as many as Germany. > How many in Europe? In Europe the police carry guns, not the next guy > who is going to object to my driving. My question for Peter is since Europe has had many extermination camps in the last century, who at the extermination camps had guns and who did not? Lots of guns in America but no extermination camps. Do think there might be a connection? Fred Townsend > > > I also happen to be a karate instructor, a professional doorman > (bouncer) and I train nurses and counsellors, working with addicts and > alcoholics off the streets, in low-arousal defence techniques and > situation de-escalation - as well as being an FIEE emc engineer. I get > scared in Houston at night (that's where an English engineer got lost, > knocked on the door of a house to ask directions and was shot dead > through the door - anyone want to talk to his wife?), but in four > years I have never faced a gun on the nightclub doors in Bristol. > Also, our gun enthusiasts do not own handguns, combat rifles or > pump-action shotguns - they still have fun. > > I will not be the only UK professional reading this thread and from > the reactions in my company, which is American owned, the ease with > which people are willing to deprive another human of their life is > shocking. > > All that said, I do not see what the topic has to do with meeting > health and safety regulations. Which standard are you referring to? > > Peter > > -Original Message- > From: Sam Davis [mailto:sda...@ptitest.com] > Sent: Tuesday, May 07, 2002 2:51 PM > To: Gert Gremmen; Pettit, Ghery; 'Ted Rook'; < > Subject: RE: stun guns on aircraft > > > This has nothing to do with EMC or Product safety, but with personal > and > public safety. > > I'm with Ghery. Gert, your misrepresentation of his statement is > ludicrous. > Statistics bear this out. Crime rates drop drastically in nations > where > guns are freely owned by the PUBLIC. Look at Australia. The gov't > took the > gun ownership rights away, and violent crime rose horribly. > > Guns are not only offensive weapons, but defensive weapons as well. > If some > criminal approaches your wife with a gun, would you prefer her to have > a > pistol, or a whistle? > > What do you want your cops to defend your streets with? What about > your > military, to guard your ability to go to work, make a living, support > your > family, without having to worry if you'll be a captive prisoner of > war, or > worse? What about the security force at your airport? > > Guns even the playing field. > > When you outlaw guns, only outlaws have guns. Law abiding citizens > turn > them in, and can no longer defend their homes with the NECESSARY > force. > Fortunately, I live in a locale where gun ownership is not only > allowed, but > almost expected. Statistically, there are more guns than people per > household. There is also a very low rate of home invasion. > Since concealed carry permits have been issued, all violent crimes > have > dropped. > > Hijackers take planes because law-abiding travelers are not packing > heat. > > I own multiple guns, legally, and I pray I never have to fire them in > self > defense, but I pray I don't have to use my AD&D policy either. > > BTW, Ted, your statement "Unfortunately America was taken by force and > is > defended by force and is unlikely ever to change", I disagree with > your > first syllable. The reason we're the prime superpower is because the > world > knows we will use it if we have to. The reason our allies like us is > because we've got their back, (and we've thrown billions of dollars to > bail > them out without actually expecting payback, but that's a completely > different thread). > > Remember grade school, who got picked on? The kid that couldn't (or > wouldn't) defend himself. The guys that were obviously able to return > > injury never had to fight. Think about that. > > If any of my statements offend you because of your national pride, I'm > > sorry. My national pride is what brought me in here. I mean no > offense to &
Re: Stun Guns on Aircraft.
the voltage. > > > 5- TASER versus Stun gun - thanks for correcting my misunderstanding - > Two > comments - First - if the stun gun is discharged through the airframe there > will be an induced potential in local electronic systems. Correction. There will be an induced current. The potential will be almost zero across the very low resistance of airframe. > Second - if I must > turn off my tape recorder (powered but a single AA cell) because it may > affect systems then how is discharging 50k considered to be safe and OK??? It may interest you to know there is no FAA requirement to turn off your tape recorder. Instead the FAA allow airlines to set their own rules. You can not prove the negative case of never, ever causing a problem but I have never seen a documented case of a problem (to flight systems) caused by a tape recorder or even a cell phone. I think the reasoning of most airlines is to error on the side of safety. Besides without the earphones in your ears you can hear the crew instructions. > > > 6- Design of interfaces to cope - some of the prototype systems that I > did > safety and reliability work on in (1995)uses surface mount components to > provide lightening protection - these devices would not provide Creepage > distances of more than a couple of millimeters. I'm not sure what your point is here. SMD does not relate to safety and usually has better reliability. > > > 7- Ground computers - I agree that this is worrying - the UK has even > more > out of date equipment and then the new system (that will control air traffic > in the South of England) used equipment (and software) purchased in the late > 80's early 90's. I just hope that it still works when they take it out of > the box. The point is that RANDOM failures exist and there procedures have > been developed (and practiced) to deal with them. Anything that induces > non-random and multiple failures is - I suggest - another ball game. > > 8- The chances are low - I agree - I was flying back from the west coast > the > morning of 9-11 and I did not get a warm fuzzy feeling about probability > when I watched the news footage - but I have made many flights since and it > will not stop me from flying. I am grateful for the fact that Europe and the > middle East are sharing their security experiences with the US. Security is > a cultural thing and the US has a long way to go before it provides the same > level of security from officials AND MORE IMPORTANTLY from passengers. I strongly agree. Fred Townsend > > > These are Gregg's four pointers to improve security at ZERO cost: > Security guards most NOT walk around together. > ALL alarms must be investigated by security (a telephone call saying OK - is > negligence). > ALL unattended baggage MUST be treated as a bomb. > ANYONE asking me to "keep and eye" on their baggage will be told to take it > with them or I will report it as a bomb. > > Security is the responsibility of everyone that flies - Please help to keep > me safe and I will do my best for everyone else. > > Best regards > > Gregg > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: Stun Guns on Aircraft.
Do you think the EMI from a stun gun can compare to the airplane being hit by lightning? World wide, airplanes are hit by lightning every day. They don't crash. Relax If you want something to worry about... worry about the FAA flight tracking computers that were built the 1970s that fail every day somewhere across the USA. Be very worried. Fred Townsend Gregg Kervill wrote: > There have been several reports here (in the US) that airlines are placing > guns or stun-guns on aircraft. > > I understand the risk of a bullet - I understand that the risk can be > reduced by using a flat, disc-shaped, rubber projectile. BUT, the though of > ANYONE discharging a stun gun on a flight deck full of mission critical > (and sometimes not well buffered) electronics scares me more that the though > of a terrorist. > > Please can someone tell me that I should not worry - or to stop flying. > > Best regards > > Gregg > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: radar
I think what you saw was a strobe light that was flashing. It has nothing to do with the mechanics, only the image. It appears that the CHP feels that when you see someone getting a ticket you speed up since you regard that officer as otherwise engaged. When you see a CHP with his radar gun cocked, everyone slows down. He doesn't even have to turn it on to be effective. In fact if he leaves it off, it enforcesthe image of steal technology that can't be detected by radar detectors. Fred Townsend Jim Freeman wrote: > Hi All, > I apologize for being off subject but I was driving to work and > noticed aCalifornia Highway Patrol officer on the opposite of the > freeway an about 500 yards away. What brought him to my attention was > what appeared to be a strobe light that was flashing. I have been > thinking about and I was wondering if the new radar has some ways of > taking pictures or if the strobe light really is the radar source. Any > help would be appreciated. > > Thanks > Jim Freeman > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson:pstc_ad...@garretson.org > Dave Healddavehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server.
Re: Something a little different - Car Radio question
This is not normal. I know of no normal situation where you would lose your AM reception. Sounds like the installer is "tuned out". Complain to Best Buy management ASAP. Fred Townsend Charles Grasso wrote: > Hello all, > > Well Xmas has come and gone and I got a nice new car stereo > for Christmas. I dutifully went up to Best Buy - had it installed > only to be informed that I can no longer receive AM. I happen > to enjoy AM radio so this was a bit of a blow. I inquired as > to what the possible cause might be and the answer I got was.. > "Some cars do this.." which is no answer at all. My car has an > antenna in the windshield and the original radio worked > just fine. I am a little confused soI thought I would ask the > expert EMC community for ideas. ANyone want to hazard a guess as to > what is going on?? > > Chas > > _ > Join the worlds largest e-mail service with MSN Hotmail. > http://www.hotmail.com > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson:pstc_ad...@garretson.org > Dave Healddavehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: Microwave Cable assembly
http://www.goreelectronics.com/products/cable_assemblies/micro_test.cfm "KC CHAN [PDD]" wrote: > Hi all > > I am looking for a K-type connector cable that is for measurement up to 26.5 > GHz, any recommendation of the suppliers? Try http://www.goreelectronics.com/products/cable_assemblies/micro_test.cfm. You can dowload a catalog covering your requirements. Keep in mind that all coax is extremely lossie at Ku band and correction factors must be used for measurements. Fred Townsend > > > By the way, does anyone know that if Horn antenna up to 40 GHz with SMA or > N-type connector available in the market? Such a high frequency range, I > think SMA or N-type might not be suitable choices. > > Thank You > KC Chan > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson:pstc_ad...@garretson.org > Dave Healddavehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: questions on strip line current carrying capacity
I'm wondering why does she want to know. Stripline is not normally used in power circuits. Are you using this in a transmitter? If so, there many factors to consider. First, there is skin effect which reduces the DC resistance considerably at high frequencies. Silver plating rather than solder is used when skin effect is a problem. Then reflection coefficients are important because standing waves greatly reduce current carrying capacity. You will want to check dielectric absorption too. Of course all of these factors vary as a function of the operating frequency. Now do you see why the books don't discuss current carrying capacity for stripline? Fred Townsend shbe...@rockwellcollins.com wrote: > Does anyone of a good reference for quantifying strip line and its current > carrying capacity? Most references I have seen primarily discuss the > calculations for characteristic impedance control only. > > Susan Beard > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson:pstc_ad...@garretson.org > Dave Healddavehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: question of flex circuit materials
>From an EMC prospective they are all the same, because they are the same! >Kapton is a Dupont trade name for polyamide. Fred Townsend shbe...@rockwellcollins.com wrote: > >From an EMC standpoint, are there any flex circuit materials (e.g., kapton > vs. polyimide vs. other) that are preferred? > > Susan Beard > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson:pstc_ad...@garretson.org > Dave Healddavehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: looking for used power supply
Brian O'Connell wrote: > Sir, > > Please do not take as flame. No incineration here. > > > I've yet to work at a company, that make products for connection to AC > mains, intended for use in multiple countries, and being both serious & > professional about testing for compliance and performance, that did not have > at least one of these instruments in the lab. Did Mike say this was his intended use? > > > Please visit the web pages of Elgar, Pacific Power, Agilent, etc. The > requirement should be obvious. I am very familiar with this type equipment. If you are familiar with this type equipment you should also know that an Elgar covering this power range, variable from say 40 to 400 Hz costs upwards of $25K, takes 5 rack bays to house, and 6 weeks to order in. On the other hand if Mike is simply looking for something to make 50 Hz from 60 Hz then a simple motor gen set costing a few $K will do the job. Finally if Mike is really trying to hook up a single phase load to a 3 phase main, then all he needs is the right transformer. <$1K The operative word here is "variable" and in what context. It seemed obvious to me that Mike was not familiar with this subject and could have mis-specificed his requirements, i.e. did he say variable when he meant compatible? Fred Townsend > > > > > -Original Message- > From: Fred Townsend [mailto:f...@poasana.com] > Sent: Thursday, May 10, 2001 1:42 PM > To: Mike Stone > Cc: emc-p...@majordomo.ieee.org > Subject: Re: looking for used power supply > > I can see why you might have difficulty finding such a device. Your > specifications are ambiguous. > Do you really mean variable frequency or the ability to operate from either > 50 or 60 Hz mains. > Ditto for variable voltage. > 3000VA makes no sense in the context of 120VAC or 230VAC at 16 amps. > > It is not clear what commercial benefit such a device would have (except to > separate a fool and his money) so I am skeptical you would ever find such a > device used. > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson:pstc_ad...@garretson.org > Dave Healddavehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://www.rcic.com/ click on "Virtual Conference Hall," --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
Re: looking for used power supply
I can see why you might have difficulty finding such a device. Your specifications are ambiguous. Do you really mean variable frequency or the ability to operate from either 50 or 60 Hz mains. Ditto for variable voltage. 3000VA makes no sense in the context of 120VAC or 230VAC at 16 amps. It is not clear what commercial benefit such a device would have (except to separate a fool and his money) so I am skeptical you would ever find such a device used. Fred Townsend Silicon Valley Mike Stone wrote: > Good Day,I am looking into purchasing a used power supply.Minimum > requirements are: 3 phase input, single phase outputvariable > frequency, 50/60 Hzvariable voltage, 120VAC, 230 VAC3 KVA16 Amps I > have tried a number of resellers, with not much luck.Thank you in > advance for your help. Best Regards, Michael Stone > L. S. Compliance > W66 N220 Commerce Court > Cedarburg, WI 53012 > V 262-375-4400 > F 262-375-4248
Re: AC Power Primer?
I can't speak for the European community but in the US the circuit you describe is single phase. If I put a phase meter or scope on it I will not be able to measure a phase difference. I can buy split phase as Jim suggests . There are split phase motors that run from a single phase that use a capacitor to shift the phase. Calling such a circuit "two phase" is somewhat dangerous in that there really are 2 phase circuits (180 degree) as well as 6 phase (65 degree) around! I suspect most of these even phased circuits are relegated to museums by now since they are holdovers from the days when the "AC boys" battled Edison's "DC" at the turn of the century. Think where we would be today if Edison had won. Fred Townsend Silicon Valley rbus...@es.com wrote: > I am in the process of assisting our publications group with documenting an > ac power configuration. As simple as this sounds, it turns out there are > varying opinions in our engineering group regarding the naming convention > for input power, in particular single phase verses two phase. > > We all probably agree that a phase to neutral connection is single phase and > devices that use all thee phases, whether they are 208V 60Hz or 400V 50Hz, > are truly three phase. The discussion heats up when you are talking about a > phase to phase connection on a three phase distribution (208 or 400V). Is > this called single phase or two phase? It has been suggested that in the > European community it is called two phase, while in the U.S. we call it > single phase. I am looking for opinions or discussion on this issue. > > On a related note in the U.S. we have 240V 60Hz (two 120V drops) coming into > our into our homes. This is provided by a transformer with a center taped > winding. On the outside legs of the transformer we have 240V but between > either outside leg and neutral (center tap) we have 120V. I would call this > a single phase system with two additive (in phase) 120V windings. Again > others have called this two phase. > > My apologies to the group if this is a stupid question. Its just one of > those nagging questions. > > Rick Busche > Evans & Sutherland > Salt Lake City, Utah > > rbus...@es.com > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson:pstc_ad...@garretson.org > Dave Healddavehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://www.rcic.com/ click on "Virtual Conference Hall," --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
Re: consumer electronics used on board aircraft
I did both the FCC and FAA submittals for the system that Qualcomm did the front end system design for. It was one of the more interesting systems I have ever worked on because of the blend of commercial avionics and consumer electronics. Let me clarify a few issues. Airborne cellar shares the same band (NOT the same frequencies) as the ground based cell systems. However, the transmitter power levels were around 25 watts making the system substantially more powerful than a ground type mobil cell phone. Therefore if there was no EMI to the aircraft systems (several octaves lower in frequency) from the airborne cell system, then it is highly unlikely the lower powered ground cell phones would cause any interference to the aircraft systems either. It was never a concern to the FAA. So why not allow ground based cell phone usage while in the air? The answer is ground based systems rely on FM radio's capture characteristic to allow very heavy frequency reuse. The low powered ground units depend on the mobil unit seeing only a few cell sites so they can reuse the same frequencies at other cell sites. The system measures the power level at the individual cell site and determines which antennae (and cell site) to use. If the power levels are saturating at more than one cell site, (as is typical when the aircraft can see many cell sites) the system can not determine which antenna to use and locks up. There are issues too. Cell sites are designed for slow moving mobiles where there is plenty of time to anticipate of the hand off to another cell site. Airborne units quickly overtake a cell sites causing existing mobil connections to be dropped. One airborne mobile cell phone can wipe out many ground mobile cell sites. So the real answer to the question of airborne mobile cell phone usage is not interference to the aircraft or aircraft navigation system; rather it is interference of ground based mobile units. Fred Townsend Brent DeWitt wrote: > It's conceivable, but the folks at Qualcomm I did base station testing for > seemed to think the problem was real, and they don't make aircraft systems. > > -Original Message- > From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf > Of rbus...@es.com > Sent: Thursday, January 25, 2001 10:26 AM > To: emc-p...@majordomo.ieee.org > Subject: RE: consumer electronics used on board aircraft > > I may regret saying this, but isn't it conceivable that the FCC Rules that > make it illegal to use a cell phone in the air has more to do with the right > of the airline to sell expensive phone time, than the technical issues? :( > > -Original Message- > From: Brent DeWitt [mailto:bdew...@ix.netcom.com] > Sent: Thursday, January 25, 2001 10:08 AM > To: Mike Hopkins; 'Colgan, Chris'; 'Emc-Pstc' (E-mail) > Subject: RE: consumer electronics used on board aircraft > > My background is the pretty much the same as Mike's, which is probably why I > agree with his response. I just wanted to add that the prohibition on cell > phone usage (in the US at least) is not FAA or airline driven, but mandated > by the FCC. The architecture of the cellular system is rather carefully > planned. The placement of antenna sites, coverage and hand-off algorithms > are based on the propagation from land based phones, which is quite > different from a phone in an airliner 25000' feet up. The FCC has therefore > made it illegal to operate a cell phone after the wheels of the plane leave > the ground. > > Regards, > > Brent DeWitt > > "Takeoffs are optional. Landings are mandatory" > > -Original Message- > From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf > Of Mike Hopkins > Sent: Wednesday, January 24, 2001 11:38 AM > To: 'Colgan, Chris'; 'Emc-Pstc' (E-mail) > Subject: RE: consumer electronics used on board aircraft > > As a frequent flyer and private pilot with some knowledge of EMC, I'll throw > in a few comments: > > It is clear to me that consumer electronics can interfere with aircraft > electronics, and I've probably heard all the same horror stories -- DC10 > finds itself off course on landing, false engine warnings, interrupted > communications, etc... It isn't clear to me how prevalent this problem is or > if it happens often enough to be considered a problem. One instance of > electronic interference is enough to have everyone up in arms against the > use of ANY electronics in ANY airplane. > > On a 747 flight to the Pacific, I'd bet there are as many as 30 to 40 lap > top computers operating together at some point during the flight. > Additionally, there are probably another 40 to 50 walkman tape players or CD > players in operation, plus the on-board
Re: VHF oscillator circuit design Questions
Sarmad you describe a complex design involving many tradeoffs that is probably beyond the scope of this forum to fully analyze. I will offer a few comments and hope that others will do the same. sarmad Albanna wrote: > Hello everyone, > > I really apprecaite any inputs on that subjects, thanks in advance: > > This is problem, I hope that I would not bore you will very much details. > > We are designing a 12 layer board that has a @ 2.5 Ghz circuit. The circuit > contains a source crystal oscillator a ~ 78 Mhz PECL signal ,this feeds into > a PECL/TTL converter (plastic with no metal case), then the output of the > converter is feeding into a CLK multilayer (plastic with no metal case)that > generated a differential output of 2.5 Ghz. All the power and Clk ( ref and > others) are on the first layer (however very short ( electrically, the > maximum length of 5 mm). The GND for all those chips are done through the > voltage return pins ONLY for each one to Digital DGND ground that is on the > 2nd layer. There is no shielding or localized grounding for those three > components. Emission is measured at 2.5 Ghz is quite high, and we relaying > the board by doing the following: > > 1. Introduce a localize GND on the 1st layer that is a solid Cu plane, all > three components will sit on that GND. The GND will have vias connected > to the DGND in the 2nd layer. > > 2. All the traces that going to and/from those chips will be buried in the > forth layer ( layer 3 is Voltage plane). So effectively will be slightly > longer than 5 mm ( <6mm)). > > 3. we are putting a metal SMT can on top this circuit will completely Seal > the components and preventing them from radiating. > > Q1. Do I need to barry those traced or can I run them through the localized > GND in the 1st layer? I'm not sure how you would do this but it sounds like you would cut up your ground plane if you ran traces through it. It sounds like your may already be floating. You have not mentioned decoupling. It is essential you decouple the RF energy from the power supply traces if you are going to keep the whole assembly from becoming an antenna. Impedance inverts every quarter wave length. Using the formula: lambda = 300M / f(MHz) we get a wavelength of 120 mm. A quarter wavelength would be 30 mm. This means a short (0 Ohms) would have infinite impedance 30 mm away. Practically, ground trace lengths of over 5 mm will be ineffective at 2.5 GHz. > > > Q2> If I need to use a heat sink on the multilayer, How can use it without > defeating the purpose of the metal RF can? What is the purpose of the metal can? Perhaps you are thinking it will serve as a shield? Not likely. With effective grounds you may be able to contain the electric fields but it will do very little to contain magnetic fields. > > > Q3> Did I miss any thing interms of the layout, for better EMC? > Electromagnetic fields are best reduced by keeping 1) current low, preventing 2) impedance discontinuities, and 3) preventing antenna like constructions. Practically there is very little you can do to control current (1) because to prevent discontinuities (2) and antennas (3) you must use matched transmission lines. (Transmission lines limit impedance (and thereby current) to a relatively narrow range.) I suggest you address these issues in your design. Transmission line rules are well embodied by microstrip or stripline construction techniques found in many texts . You do not mention any of these terms in your proposed solution so it is unlikely your changes will produce good EMC. > > Q4> how much should I expect of reduction in EM radiation, when adding that > change? It sounds like your changes are a start in the correct direction but it is not clear you will have any reduction. It may be better or again it may be worse. Fred Townsend Consultant f...@poasana.com > > Any helpful inputs will be very appreciated. > > THanks very much for your responses. > > Sami Alkar > Compliance Engineer > samii...@hotmail.com > > _ > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. > > Share information about yourself, create your own public profile at > http://profiles.msn.com. > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson:pstc_ad...@garretson.org > > For policy quest
Re: Common Mode Choke
I've read your message twice and I still don't get your point. Saturation is a disaster, EMI wise, (not to mention what it can do to the current in some semiconductor devices) so as a designer you have to make sure you never go there. If you have a 6 amp peak current then use a choke rated for 6 amps RMS. Using any device outside it's rated parameters is cruising for a bruising. Fred Townsend DC to Light Consulting Services Derek Walton wrote: > Good day all, > > I'm refining the input filter of a 150 watt SMPS. Nothing flashy, just a > few caps and a common mode choke. > > The current is drawn by the supply in short bursts as the DC link cap is > charged. I've shown that peak current reaches 6 amps for up to 2 ms. > I've also demonstrated that the CM choke, while rated for the RMS > current ( a 2 amp device ), does saturate when the current exceeds about > 4 amps. > > I've been trying to find out from the vendors, what current it takes to > saturate the CM choke. I've had answers from CM chokes can't saturate to > "that's not an important parameter, use the rms figure" > > My question is, with over 20 potential vendors of this type of > component, is there any way I can find out saturation performance > without buying one of each type and testing it. I've played with 3 so > far, the most expensive was NOT the best! I guess, I'm curious why more > folks don't know about this effect also. > > Thanks, > > Derek Walton > Owner > L. F. Research EMC Design and Test Facility > 12790 Route 76, > Poplar Grove, > IL 61065. > www.lfresearch.com > > - > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > jim_bac...@monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Rodents et al
Where are the Texans? I thought the snake stories always brought the "They're bigger in Texas" stories. Brian Harlowe wrote: > Just to add a note from the European side of the pond regarding > "wildlife and cables" > > In another life I was involved in installing some towers with cables > going up them in a remote part of the North of Scotland. > > The local sheep got a taste for PVC and we had to put metal sheathing > up to 10 ft over the cables to stop them getting to the insulation. > > The only other advantage was that apart from the occassional bite the > end effects were not fatal > > Brian Harlowe > * opinions expressed here are personal and in no way reflect the position of > VG Scientific > > - > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > jim_bac...@monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Altitude
rbus...@es.com wrote: > > This is not a safety or EMI question, but because this group has such > broad backgrounds and diversity I am hoping that someone can comment. > > I have been asked by one of our customers to ensure that our equipment > is capable of being shipped in an un-pressurized aircraft for altitudes > of 30K to 40 K feet. This is a non operational requirement, but are > there other concerns I should be aware of? I recall hearing that some > commercial grade electrolytic could explode at high altitudes. Your concerns are valid. Not just electrolytic. Many types of electronic components, particularly capacitors, will fail, usually not explosively, just a latent defect as Robert Macy describes. Most components are certified for operation or storage to 10K feet. You can sometimes find parts certified for high vacuum but I doubt if you will find electrolytics. Your solution is to specify only pressured cargo airplanes. I am told that most airplanes are pressurized in the cargo area but I have not idea which airplanes are not. Fred Townsend DC to Light Silicon Valley
Re: Noise in Power Lead
Bob Tims wrote: > > Happy New Year All, > > I have an interesting noise problem brought to me. > The noise is a 500-900 mV pulse seen at 50 MHz on a > power lead from a DC to DC converter (48V to 5V) to a > VME cage. > There were two scenarios: first, both the power supply > and the cage are earth-grounded, and the pulse is seen > at both the power supply and the cage. Second, the cage > is left floating, and the pulse is only seen at the > power supply. > The noise seems to be a ring, and the leads between the > supply and cage are fairly long. > Has anybody seen something like this before, or does anybody > have any suggestions or comments? > We have several ideas, but not much time. > The frequency and the fact that the pulse reaches almost a volt > concerns us greatly. You didn't say how you are measuring .5-.9 volts but about the only thing you can be sure of is things are not as you have indicated. For instance if we had just one 0.01uf bypass capacitor across this power lead, its reactance at 50 MHz = 1/(2pi f C) = 0.31 ohms It's highly unlikely the noise source could drive almost a volt into this reactance. It is more likely you have a common mode propagation along the cable. It's also likely you are measuring the common rejection factor, or lack thereof, in your measuring instrument. (scope?) If so, slapping a common choke (ferrite block) on the cable should change the reading. You may need to place the converter in a Faraday shield with an appropriate RFI filter on the power I/O to block the noise. I suggests you look up Henry Ott's book on noise. He suggests so methods for tracing your problems. Fred Townsend DC to Light Consulting f...@luxtron.com
Re: Positions Available For EMC Engineers/Technicians
Gentleman: Please accept this criticism in the friendly spirit it is intended. IMHO, your ad does not give the potential applicant any reason to apply. Nothing about your company and Northern California is a large area. I know, I live there. It's bigger than several states. In case you haven't figured it out by the lack of response, it's a seller's market. Mark Briggs wrote: > > ** Positions Available In Northern California For EMC > Technicians/Engineers ** > > Openings for Technicians and Engineers, with either an EMC or RF > background, to perform EMC emissions/immunity testing and debug. > Experience preferred, but all prospective employees with the right > aptitude and attitude will be considered. > > > EMail resumes to: epa...@elliottlabs.com > Fax resumes to: (408) 245 7800 > > ** Positions Available In Northern California For EMC > Technicians/Engineers ** > > Mark Briggs > mbri...@elliottlabs.com
