Re: Teslars???
To be pedantic, you are mixing units of two different quantities there Mike. Tesla and gauss are units of magnetic flux density, the B field Ampere/metre and oersted are units of magnetic field strength, the H field. Only in a vacuum does 1A/m generate a flux density of exactly 0.4 pi µT In air its pretty close but in ferromagnetic materials it can be thousands of times bigger. The field strengths mentioned in the original question are not all that outrageous. Most transformers, motors and generators with electrical steel laminations operate at peak flux densities of 1.4T to 1.7T within the core. At a boundary between two materials of different permeabilities the tangential component of H and the normal component of B are the same either side of the boundary. The amplitude relative permeability of electrical steels near their maximum working flux density is only about 300 to 800. So with the flux flowing along the core at a flux density of say 1.5T and an amplitude relative permeability of 500, you get a flux density close to the core surface of 3mT. While you are in the near field (distances small with respect to the size of the magnetic circuit) this will not drop very fast. in the far field it drops according to the inverse cube dipole law. Things are even worse at the corners. The flux does not turn smart right angles just because the core does and so the flux is not parallel to the core. This increases the flux density close outside the core. Worse yet are the effects of gaps. Laminations in transformers are commonly made in two parts that fit together to form the complete lamination. C & T shape or E and I shape. This is done so that the winding can be put on the bobbin first and then the core built up. Where the two parts of the lamination meet up there is always a small gap the size of which depends on the quality of the laminations and the care with which the core is assembled. Good practice is to alternate the orientation of the laminations so that the gaps do not align but in some cheap devices the laminations are stacked up with the gaps aligned.These devices also tend to be those using poorly cut laminations. Gaps of half a millimetre are not unknown.they also tend to push the flux density up closer to the limit increasing the external flux even more because of the lower amplitude relative permeability Gaps in rotating machines can be even bigger . Since the flux crosses the gap almost normally the flux in the gap is the same as in the core 1.4T -1.7T At the edge of the core this flux bulges out into a fringing field. Fortunately this enters the far field dipole law at distances large compared to the gap length and width. Even so fields of tens of mT can be found within a few centimetres of the gap. So take a large poorly built transformer or solenoid and push the core hard up against the equipment housing and you could well exceed 0.7 mT nearby. Several metres from a train is a bit less likely but not impossible These figures should be borne in mind the next time you read about the dangers of the magnetic field from overhead power lines. I have several times seen building site welders sitting on their transformers with their testicles dangling over the gap and I haven't seen welders dropping like flies. Nick Rouse - Original Message - , From: "Mike Cantwell" To: "emc-pstc (E-mail)" Sent: Friday, February 08, 2002 2:53 PM Subject: RE: Teslars??? > > > I think the units you're looking to compare to would be Amps/meter. The > conversion from Tesla to A/m is: > > 1 A/m = 1.26 uT = 0.0126 Gauss > > Therefore, a field of .7 mT converts to 555 A/m !!! (it is also equivalent > to 10 Gauss) > > Assuming that your customer is referring to power frequency magnetic fields, > this would be substantial, to say the least. > > I would recommend that you question your customer a little further as to how > they determined this field strength requirement. It seems high by a factor > of about 1000. > > Good luck, > Mike > > -Original Message- > From: marti...@appliedbiosystems.com > [mailto:marti...@appliedbiosystems.com] > Sent: Thursday, February 07, 2002 4:22 PM > To: emc-p...@majordomo.ieee.org > Subject: Teslars??? > > > > We have a customer that is concerned about how our product, laboratory > equipment, will respond to electromagnetic disturbances from a high speed > train that runs close to their lab. The customer states that the > disturbance will be around 0.7-1.2 m Teslar. > > Can someone please explain what the unit Teslar is and how that unit > relates, or if it relates, to the immunity tests of EN 61000-4-3 Radiated > immunity, or any other immunity test. > > Has anyone ever had a similar concern from a customer dealing with this > type of disturbance? > > Your responses are appreciated. > &g
RE: Teslars???
I think the units you're looking to compare to would be Amps/meter. The conversion from Tesla to A/m is: 1 A/m = 1.26 uT = 0.0126 Gauss Therefore, a field of .7 mT converts to 555 A/m !!! (it is also equivalent to 10 Gauss) Assuming that your customer is referring to power frequency magnetic fields, this would be substantial, to say the least. I would recommend that you question your customer a little further as to how they determined this field strength requirement. It seems high by a factor of about 1000. Good luck, Mike -Original Message- From: marti...@appliedbiosystems.com [mailto:marti...@appliedbiosystems.com] Sent: Thursday, February 07, 2002 4:22 PM To: emc-p...@majordomo.ieee.org Subject: Teslars??? We have a customer that is concerned about how our product, laboratory equipment, will respond to electromagnetic disturbances from a high speed train that runs close to their lab. The customer states that the disturbance will be around 0.7-1.2 m Teslar. Can someone please explain what the unit Teslar is and how that unit relates, or if it relates, to the immunity tests of EN 61000-4-3 Radiated immunity, or any other immunity test. Has anyone ever had a similar concern from a customer dealing with this type of disturbance? Your responses are appreciated. Regards Joe Martin EMC/Product Safety Engineer Applied Biosystems marti...@appliedbiosystems.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...@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://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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
RE: Teslars???
There are a series of ENs, 50121, relating to EMC requirements for "railway equipment". That's all I know - I just noted in my records back in 1997 that they were starting to appear. I also note in EN 61000-4-8 Power frequency magnetic field immunity, that 1 A/m corresponds to a free space induction of 1.26 uT, and test levels of 1, 3, 10, 30, and 100 A/m are given for continuous field. Regards, John Crabb, Development Excellence (Product Safety) , NCR Financial Solutions Group Ltd., Discovery Centre, 3 Fulton Road, Dundee, Scotland, DD2 4SW E-Mail :john.cr...@scotland.ncr.com Tel: +44 (0)1382-592289 (direct ). Fax +44 (0)1382-622243. -Original Message- From: marti...@appliedbiosystems.com [mailto:marti...@appliedbiosystems.com] Sent: 07 February 2002 22:22 To: emc-p...@majordomo.ieee.org Subject: Teslars??? We have a customer that is concerned about how our product, laboratory equipment, will respond to electromagnetic disturbances from a high speed train that runs close to their lab. The customer states that the disturbance will be around 0.7-1.2 m Teslar. Can someone please explain what the unit Teslar is and how that unit relates, or if it relates, to the immunity tests of EN 61000-4-3 Radiated immunity, or any other immunity test. Has anyone ever had a similar concern from a customer dealing with this type of disturbance? Your responses are appreciated. Regards Joe Martin EMC/Product Safety Engineer Applied Biosystems marti...@appliedbiosystems.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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: Teslars???
I read in !emc-pstc that Robert Macy wrote (in <013301c1b033$eed45cc0$69e10...@robert.macy.california.com>) about 'Teslars???', on Thu, 7 Feb 2002: > If you're English, 1 tesla is 10,000 gauss. It is, but electronic engineers in Britain use SI units. Magnetic materials suppliers, world-wide, still use CGS units, as do most physicists, it seems, judging by the papers in 'Nature'. They probably get a kick out of writing things like '10^38 ergs'. Since you are in USA, I am surprised that you don't use a unit called, perhaps, the 'franklin', 1 pound force per ampere-foot. (;-) -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. PLEASE do NOT copy news posts to me by E-MAIL! --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: Teslars???
I read in !emc-pstc that Robert Macy wrote (in <013301c1b033$eed45cc0$69e10...@robert.macy.california.com>) about 'Teslars???', on Thu, 7 Feb 2002: >I don't believe those numbers. We have light rail train go by here which is >powered by 600Vac (I believe it's 600 Vac) I haven't seen the fields from >the motors, only the fields from the disturbance to the earth's field >(approx 50uT) as it is being deflected by the large metal vehicles. Much >more an effect than from the power source. > >If those specs you quoted go down to 50 Hz or 60Hz, than they relate, >otherwise doubt if you'lll easily relate them. It would be "susceptibility >to AC mains magnetic fields." > >Might also look at the Swedish MPR II, or is that III now? The limit for a >monitor radiating is 200nT in this bandwidth. > >Underneath high tension wires I've seen fields around 100mG, which >translates to 10uT! and those fields are considered big. > >Again, I question those specs. Maybe they meant 0.6 to 1.7 microtesla. The field due to traction current in overhead power conductors creates a magnetic field that can, for example, disturb CRT displays. Let us assume a distance of r = 10 m between the conductor and the display. The induction B is related to the current I by B = [mu]I/2[pi]r. [mu] is the permeability of free space, 4[pi] x 10^-7 H/m. To get 1 mT at 10 m, the current would need to be 50 000 A. This seems unlikely! Note that in some countries the traction current is not 50 or 60 Hz but 16.67 Hz. There are also still some systems using d.c. This does not affect the induction but does affect the immunity (if any!) shown by the equipment. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. 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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: Teslars???
Martin, I believe they were saying Tesla (units of magnetic flux density) 1 Tesla = 10,000 gauss so 1 mTesla = 10 gauss There is a relationship between flux density (B) and magnetic field (H) in A/m B = mu H (Greek letter mu represents permeability of the material) EN 61000-4-8 for power line magnetic field immunity testing is probably what your customer would like to see. This test is commonly done for devices using Hall effect transducers, coil transducers or which use magnetic field deflection techniques (CRT products) best regards Tom Cokenias T.N. Cokenias Consultingt...@tncokenias.org P.O. Box 1086 El Granada CA 94018 tel 650 726 1263 cell 650 302 0887 fax 650 726 1252 At 2:21 PM -0800 2/7/2002, marti...@appliedbiosystems.com wrote: We have a customer that is concerned about how our product, laboratory equipment, will respond to electromagnetic disturbances from a high speed train that runs close to their lab. The customer states that the disturbance will be around 0.7-1.2 m Teslar. Can someone please explain what the unit Teslar is and how that unit relates, or if it relates, to the immunity tests of EN 61000-4-3 Radiated immunity, or any other immunity test. Has anyone ever had a similar concern from a customer dealing with this type of disturbance? Your responses are appreciated. Regards Joe Martin EMC/Product Safety Engineer Applied Biosystems marti...@appliedbiosystems.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...@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://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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: Teslars???
In the MKS system of units, also known as SI(International System), 1 Tesla = 1 Weber per square meter. Relating it to more usual units, 1 T = 10,000 Gauss, which was the unit in the older cgs measurement system. The equation defining the relationship between magnetic field and the currents which cause them is B = uH, where B is the magnetic induction field in Tesla or Wb/m^2, H is the magnetic field in Amperes per meter, and u (actually Greek letter mu) is the permeability of the medium, which is the relative permeability of the medium (a dimensionless number) multiplied by the permeability of free space or non-magnetic materials which in the MKS system is 4*pi* 1e-7 Henries per meter. Hope that's all perfectly clear... on 2/7/02 5:21 PM, marti...@appliedbiosystems.com at marti...@appliedbiosystems.com wrote: > > We have a customer that is concerned about how our product, laboratory > equipment, will respond to electromagnetic disturbances from a high speed > train that runs close to their lab. The customer states that the > disturbance will be around 0.7-1.2 m Teslar. > > Can someone please explain what the unit Teslar is and how that unit > relates, or if it relates, to the immunity tests of EN 61000-4-3 Radiated > immunity, or any other immunity test. > > Has anyone ever had a similar concern from a customer dealing with this > type of disturbance? > > Your responses are appreciated. > > Regards > > Joe Martin > EMC/Product Safety Engineer > Applied Biosystems > marti...@appliedbiosystems.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...@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://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" > -- 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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
RE: Teslars???
I did a search on Hotbot to see what a Teslar is. Some interesting references come up about watches and protection against EMFs. Here is an example: < http://www.lessemf.com/schumann.html > Regards, +=+ |Ronald R. Wellman|Voice : 408-345-8229 | |Agilent Technologies |FAX : 408-553-2412 | |5301 Stevens Creek Blvd.,|E-Mail: ron_well...@agilent.com| |Mailstop 54L-BB |WWW : http://www.agilent.com | |Santa Clara, California 95052 USA| | +=+ | "Common sense is the collection of prejudices acquired by age | | eighteen." - Albert Einstein | +=+ -Original Message- From: marti...@appliedbiosystems.com [mailto:marti...@appliedbiosystems.com] Sent: Thursday, February 07, 2002 2:22 PM To: emc-p...@majordomo.ieee.org Subject: Teslars??? We have a customer that is concerned about how our product, laboratory equipment, will respond to electromagnetic disturbances from a high speed train that runs close to their lab. The customer states that the disturbance will be around 0.7-1.2 m Teslar. Can someone please explain what the unit Teslar is and how that unit relates, or if it relates, to the immunity tests of EN 61000-4-3 Radiated immunity, or any other immunity test. Has anyone ever had a similar concern from a customer dealing with this type of disturbance? Your responses are appreciated. Regards Joe Martin EMC/Product Safety Engineer Applied Biosystems marti...@appliedbiosystems.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...@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://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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: Teslars???
That's Tesla, which is a weber per sq meter. It is a measure of the B field, flux per area. If you're English, 1 tesla is 10,000 gauss. I don't believe those numbers. We have light rail train go by here which is powered by 600Vac (I believe it's 600 Vac) I haven't seen the fields from the motors, only the fields from the disturbance to the earth's field (approx 50uT) as it is being deflected by the large metal vehicles. Much more an effect than from the power source. If those specs you quoted go down to 50 Hz or 60Hz, than they relate, otherwise doubt if you'lll easily relate them. It would be "susceptibility to AC mains magnetic fields." Might also look at the Swedish MPR II, or is that III now? The limit for a monitor radiating is 200nT in this bandwidth. Underneath high tension wires I've seen fields around 100mG, which translates to 10uT! and those fields are considered big. Again, I question those specs. Maybe they meant 0.6 to 1.7 microtesla. - Robert - Robert A. Macy, PEm...@california.com 408 286 3985 fx 408 297 9121 AJM International Electronics Consultants 619 North First St, San Jose, CA 95112 -Original Message- From: marti...@appliedbiosystems.com To: emc-p...@majordomo.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: Thursday, February 07, 2002 3:15 PM Subject: Teslars??? > >We have a customer that is concerned about how our product, laboratory >equipment, will respond to electromagnetic disturbances from a high speed >train that runs close to their lab. The customer states that the >disturbance will be around 0.7-1.2 m Teslar. > >Can someone please explain what the unit Teslar is and how that unit >relates, or if it relates, to the immunity tests of EN 61000-4-3 Radiated >immunity, or any other immunity test. > >Has anyone ever had a similar concern from a customer dealing with this >type of disturbance? > >Your responses are appreciated. > >Regards > >Joe Martin >EMC/Product Safety Engineer >Applied Biosystems >marti...@appliedbiosystems.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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: Teslars???
Hi Joe: > We have a customer that is concerned about how our product, laboratory > equipment, will respond to electromagnetic disturbances from a high speed > train that runs close to their lab. The customer states that the > disturbance will be around 0.7-1.2 m Teslar. I believe you mean "tesla" (with a lower-case t), not "Teslar." The symbol for tesla is upper case T. According to ISO Standards Handbook 2, the tesla is a unit of magnetic flux density. "The magnetic flux density is an axial vector quantity such that the force exerted on an element of current is equal to the vector product of this element and the magnetic flux density." 1 T = 1 N/(A*m) 1 T = 1 Wb/m^2 1 T = 1 V*s/m^2 I'm sure your customer is referring to an electric train. I recall a suburban electric train line where the stations had color TV monitors to announce the train and its schedule. A few minutes before the train arrived in the station (and usually before you could see the train), the monitor's colors would go awry. The degradation would increase until the train arrived, at which time the normal colors were restored. Upon departure, the colors would again go awry, and then gradually return to normal. The color degradation was due to the magnetic field around the overhead wire. Best regards, Rich --- 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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
