emi shielding
hello: as we know, threre are two main component of shielding effectiveness. (Absorbtion and Reflection). is there any way to find out.. what percentage of overall shielding is due to absorbtion / reflection for a given material? thank you in advance. Vijay Wani Dow Chemical --- 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: emi shielding
If you are using the coaxial test fixture per the ASTM SE test method you could insert a directional coupler with reverse power tap just before the fixture and measure how much power is getting splashed back. With that number, plus the total loss in the system measured as the power getting through the fixture vs. the known power out of the signal source, you can back out what is reflected and what is absorbed. -- >From: "Wani, Vijay (V)" >To: "'emc-p...@majordomo.ieee.org'" , "'si-l...@freelists.org'" >Subject: emi shielding >Date: Fri, Nov 9, 2001, 9:36 AM > > > hello: > > as we know, threre are two main component of shielding effectiveness. > (Absorbtion and Reflection). is there any way to find out.. what percentage > of overall shielding is due to absorbtion / reflection for a given material? > > thank you in advance. > > Vijay Wani > Dow Chemical > > --- > 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: emi shielding
Absorbtion loss is given by A(dB) = 3.34 t (f(Mhz)Gu) where t = thickness in mils (sorry, my book is not metric based) G = conductivity relative to copper (G = 1 for copper) u = relative permeability to vacuum Reflection loss is given by R(dB) 20 log [(K_1)^2/4K] which is approx 20 log [Z(w)/4Z(b)] for K>10 where Zw is the wave impedance and Zb is the surface impedance. For plane waves R(dB) = 108 + 10 log [G/uf(MHZ)] All this is from EMC Handbook, Vol 3, Don White Consultants, 1973. Richard Woods Sensormatic Electronics Tyco International -Original Message- From: Wani, Vijay (V) [mailto:vw...@dow.com] Sent: Friday, November 09, 2001 10:36 AM To: 'emc-p...@majordomo.ieee.org'; 'si-l...@freelists.org' Subject: emi shielding hello: as we know, threre are two main component of shielding effectiveness. (Absorbtion and Reflection). is there any way to find out.. what percentage of overall shielding is due to absorbtion / reflection for a given material? thank you in advance. Vijay Wani Dow Chemical --- 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.
[SI-LIST] Re: emi shielding
The mechanism for reflection is that em fields incident on a surface induce currents to flow such that the flow of current opposes the field which caused it. The material must have enough absorption and homogeneity (i.e., limited apertures) such that the induced currents remain on the side of the material where they were induced and do not re-radiate. That is the function of absorption and aperture control above 30 MHz. -- >From: "Wani, Vijay (V)" >To: "'ghery.pet...@intel.com'" , "'emc-p...@majordomo.ieee.org'" , "'si-l...@freelists.org'" >Subject: RE: [SI-LIST] Re: emi shielding >Date: Fri, Nov 9, 2001, 11:52 AM > > > all:thanks for your time and response. > > I understand the frequency range we worry about (30MHz - 2GHz), any metal > (or metallized plastic) would be overkill and effect of apertures will be > mostly determing factor for shielding effectiveness. > but, the shielding mechanism of conductive metals (or metallized plastics) > is mostly reflective rather than absorbtion. > > if we have a meterial with absorbtion shielding mechanism (in 30 MHz-2GHz > frequency range), is there any advantage? i would guess, that will reduce > antenna effect in the system. would appreciate any thoughts. > > vijay wani > Dow Chemical > > -Original Message- > From: Pettit, Ghery [mailto:ghery.pet...@intel.com] > Sent: Friday, November 09, 2001 12:14 PM > To: 'Wani, Vijay (V)'; 'emc-p...@majordomo.ieee.org'; > 'si-l...@freelists.org' > Subject: [SI-LIST] Re: emi shielding > > > Vijay, > > The relative proportions are a function of frequency and the relative > conductivity and relative permittivity of the material. > > The attached file is from a MathCAD 7.0 model that I put together a while > back. The equations came from a Technit design guide published about 20 > years ago. > > You will note that in the frequency range that we usually worry about almost > any metal you might use is overkill. It is the apertures that create the > problems. The example in the document is copper. > > I hope this helps. > > Ghery Pettit, NCE > > > > -Original Message- > From: Wani, Vijay (V) [mailto:vw...@dow.com] > Sent: Friday, November 09, 2001 7:36 AM > To: 'emc-p...@majordomo.ieee.org'; 'si-l...@freelists.org' > Subject: emi shielding > > > > hello: > > as we know, threre are two main component of shielding effectiveness. > (Absorbtion and Reflection). is there any way to find out.. what percentage > of overall shielding is due to absorbtion / reflection for a given material? > > thank you in advance. > > Vijay Wani > Dow Chemical > > --- > 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. > > > > > -- > To unsubscribe from si-list: > si-list-requ...@freelists.org with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > http://www.freelists.org/webpage/si-list > > For help: > si-list-requ...@freelists.org with 'help' in the Subject field > > List archives are viewable at: > http://www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: >http://www.qsl.net/wb6tpu > > > --- > 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:pst
[SI-LIST] Re: emi shielding
Vijay, The relative proportions are a function of frequency and the relative conductivity and relative permittivity of the material. The attached file is from a MathCAD 7.0 model that I put together a while back. The equations came from a Technit design guide published about 20 years ago. You will note that in the frequency range that we usually worry about almost any metal you might use is overkill. It is the apertures that create the problems. The example in the document is copper. I hope this helps. Ghery Pettit, NCE -Original Message- From: Wani, Vijay (V) [mailto:vw...@dow.com] Sent: Friday, November 09, 2001 7:36 AM To: 'emc-p...@majordomo.ieee.org'; 'si-l...@freelists.org' Subject: emi shielding hello: as we know, threre are two main component of shielding effectiveness. (Absorbtion and Reflection). is there any way to find out.. what percentage of overall shielding is due to absorbtion / reflection for a given material? thank you in advance. Vijay Wani Dow Chemical --- 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. -- To unsubscribe from si-list: si-list-requ...@freelists.org with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-requ...@freelists.org with 'help' in the Subject field List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu
[SI-LIST] Re: emi shielding
Vijay, Check out FloEMC, http://www.floemc.com/. You can have the software determine this by integrating the losses in the material, whether they are resistive or dielectric to find the absorption. Jeff Walden -- To unsubscribe from si-list: si-list-requ...@freelists.org with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-requ...@freelists.org with 'help' in the Subject field List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu
RE: [SI-LIST] Re: emi shielding
all:thanks for your time and response. I understand the frequency range we worry about (30MHz - 2GHz), any metal (or metallized plastic) would be overkill and effect of apertures will be mostly determing factor for shielding effectiveness. but, the shielding mechanism of conductive metals (or metallized plastics) is mostly reflective rather than absorbtion. if we have a meterial with absorbtion shielding mechanism (in 30 MHz-2GHz frequency range), is there any advantage? i would guess, that will reduce antenna effect in the system. would appreciate any thoughts. vijay wani Dow Chemical -Original Message- From: Pettit, Ghery [mailto:ghery.pet...@intel.com] Sent: Friday, November 09, 2001 12:14 PM To: 'Wani, Vijay (V)'; 'emc-p...@majordomo.ieee.org'; 'si-l...@freelists.org' Subject: [SI-LIST] Re: emi shielding Vijay, The relative proportions are a function of frequency and the relative conductivity and relative permittivity of the material. The attached file is from a MathCAD 7.0 model that I put together a while back. The equations came from a Technit design guide published about 20 years ago. You will note that in the frequency range that we usually worry about almost any metal you might use is overkill. It is the apertures that create the problems. The example in the document is copper. I hope this helps. Ghery Pettit, NCE -Original Message- From: Wani, Vijay (V) [mailto:vw...@dow.com] Sent: Friday, November 09, 2001 7:36 AM To: 'emc-p...@majordomo.ieee.org'; 'si-l...@freelists.org' Subject: emi shielding hello: as we know, threre are two main component of shielding effectiveness. (Absorbtion and Reflection). is there any way to find out.. what percentage of overall shielding is due to absorbtion / reflection for a given material? thank you in advance. Vijay Wani Dow Chemical --- 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. -- To unsubscribe from si-list: si-list-requ...@freelists.org with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-requ...@freelists.org with 'help' in the Subject field List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu --- 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.
Thin metallic sheet for efficient EMI shielding
Hello All, We are looking for a not common kind of a very thin metallic sheet with a special shape to be used inside the chassis of amplifiers, over the thin-walls which separate the different PCB sections. Thus, we try to achieve a perfect electric contact between the thin metallic sheet and the thin-walls and hence, an efficient EMI shielding. The main features of this thin sheet should be: -Material: Bronze-Beryl (or maybe Copper-Beryl) -Great elasticity, to overcome the differences in height of the thin-walls. -It mustn´t become deformed after pressing it. -Application: TV distribution amplifiers of big size (40x50 cm2). Questions: 1.- We consider that the shape of this thin sheet should be with straight corrugations or ondulations (ups and downs), like an accordion. Do you agree? 2.- Does anybody know the name of any company which manufacture and/or distribute this kind of material? (all over the world, but preferably in Europe-Spain). Any help would be greatly appreciated. Thanks in advance. Jacobo Campos jcam...@tsc.uvigo.es R&D Engineer Televes, Spain - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.com with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, ri...@sdd.hp.com, or roger.volgst...@compaq.co (the list administrators).
Re: Thin metallic sheet for efficient EMI shielding
Jacobo, Try Instrument Specialties. Their Belgium office is at +32 41 877170. They make beryllium copper strips as well as elastomeric and woven wire gaskets. Dick Shultz On 9/9/98 6:16 AM ANT said >Hello All, > >We are looking for a not common kind of a very thin metallic sheet with a >special shape to be used inside the chassis of amplifiers, over the >thin-walls which separate the different PCB sections. Thus, we try to >achieve a perfect electric contact between the thin metallic sheet and >the thin-walls and hence, an efficient EMI shielding. > >The main features of this thin sheet should be: > -Material: Bronze-Beryl (or maybe Copper-Beryl) > -Great elasticity, to overcome the differences in height of the > thin-walls. > -It mustn¥t become deformed after pressing it. > -Application: TV distribution amplifiers of big size (40x50 cm2). > >Questions: > >1.- We consider that the shape of this thin sheet should be with straight >corrugations or ondulations (ups and downs), like an accordion. >Do you agree? > >2.- Does anybody know the name of any company which manufacture and/or >distribute this kind of material? (all over the world, but preferably >in Europe-Spain). > >Any help would be greatly appreciated. Thanks in advance. > >Jacobo Campos >jcam...@tsc.uvigo.es >R&D Engineer >Televes, Spain > >- >This message is coming from the emc-pstc discussion list. >To cancel your subscription, send mail to majord...@ieee.com >with the single line: "unsubscribe emc-pstc" (without the >quotes). For help, send mail to ed.pr...@cubic.com, >ri...@sdd.hp.com, or roger.volgst...@compaq.co (the list >administrators). > > - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.com with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, ri...@sdd.hp.com, or roger.volgst...@compaq.co (the list administrators).
[PSES] Surface Resistance Test of metal used for EMI shielding
Dear List Members, At an EMC lab several years ago I was shown that to properly check for continuity of metal shielding and parts that one needed to just set the probes of an Ohm meter on the surface to be measured, Do not push the probe tips into the surface. Could anyone point to a standard or published technical procedure to correctly perform "Surface Resistance Testing." Thank you in advance for reply's. Chuck August-McDowell NOTICE: This email may contain confidential information. Please see https://meyersound.com/legal/#email-ms for our complete policy. - 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://www.ieee-pses.org/list.html (including how to unsubscribe) 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:
