re: Germanium & ITO Window shielding effectiveness
Thanks everyone for your replies. Regards Andy Andrew Price Principal Development Engineer (EMC Specialist) BAE SYSTEMS Avionics A125 Christopher Martin Road Basildon, Essex SS14 3EL tel: +44 (0) 1268 883308 email: andrew.p.pr...@baesystems.com This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Germanium & ITO Window shielding effectiveness
Regarding the snippet below from Mr. Maxwell. There is no question and no argument that transitioning from milli- or micro-ohms per square to 14 Ohms per square will cause aperture or seam leakage and a degradation of shielding effectiveness (SE) relative to a contiguous low impedance shield. I was simply saying that 14 Ohms per square will preserve some enclosure SE, it is not completely useless. We are saying the same thing, but like the optimist and the pessimist viewing the glass whose volume is 50% occupied, we see it as either half full or half empty... Which view is more useful depends on how much enclosure SE is necessary for a given design, and how close the ITO gets the designer to his goal. > From: "Chris Maxwell" > Date: Fri, 17 Sep 2004 09:10:36 -0400 > To: "John Woodgate" , > Subject: RE: Germanium & ITO Window shielding effectiveness > > Will ITO provide some shielding? Sure 14 ohms/square will provide an > impedance mismatch with air. You'll get some reflection of plane waves. > But think about some of the other requirements of good shielding. A > well shielded enclosure needs to treat seams and aperatures so that they > won't radiate according to Babinet's principle. For instance, consider > a metal enclosure with an ITO coated window. As surface currents flow > on the enclosure, they will encounter the window. Most of the current > will flow around the window, since the conductivity of the metal is > orders of magnitude below the ITO. When the current flows around the > window, you have charge acceleration (it changes direction)...which > yields radiation. This is why I said ITO isn't so great for shielding. > It provides some, but not much. 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Germanium & ITO Window shielding effectiveness
Forum, I apparently did not express myself as clearly as I would have liked, at least for Mr. Gourari. I said that IF a shield can be arranged so as to cause eddy currents to flow that you would get shielding out of it, even with unity relative permeability. That is a demonstrable statement of fact, as in the magnetic loop shielding example I gave. It is also true, as Mr. Gourari states, that the use of a high permeability shielding material of the same conductivity would increase the shielding effectiveness (SE). One should not draw the conclusion from my earlier message that high permeability materials are never useful, but rather that they are not always necessary. One cannot always arrange a shield so as to induce the flow of eddy currents, and an eddy current-based shield cannot protect against dc fields. In both of these cases, if shielding is required then a high permeability material is necessary. Next, it is not true that an absence of several skin depths means no SE. It means little SE from absorption. Recall that Shelkunoff shielding theory defines total shielding as the product of three different types of shielding. Expressed in log space: S = R + A + B where all quantities are expressed in dBs. S = total shielding R = shielding from reflection (resistivity of shield material vs. wave impedance) A = shielding from absorption (skin depth) B= losses due to re-reflection within the shielding material Even if the value of A = 0, the value of S will still reflect reflection losses. Going back to my magnetic loop electrostatic shielding example, I said that if the shield were made contiguous the pickup of the loop would decrease significantly and that represents shielding without permeability. It is not clear to me what Mr. Gourari means by saying, "Otherwise eddy currents in your shield will not compensate impinging magnetic flux fully." Fully meaning infinite dB? Agreed. Fully meaning not as much SE as if there were absorption? Also agreed. It remains there is significant reflection-based SE when a high conductivity, low permeability material allows eddy currents to flow. Ken Javor > From: "Gourari, Alexandre" > Date: Fri, 17 Sep 2004 13:37:53 +0100 > To: emc-p...@ieee.org > Subject: RE: Germanium & ITO Window shielding effectiveness > > Ken, > > Your approach about eddy currents somewhat true, but not all. We would never > be in need of hign-mu materials then. You forget about skin effect that > limits your shielding effectiveness. As long as can provide enough material > thickness >> skin effect depth you are home free. Otherwise eddy currents in > your shield will not compensate impinging magnetic flux fully. Look at the > skin depth formula > h = ((2*r)/(2*pi*f*u))^0.5 > where r-resistivity (Ohm*in), f - impinging wave frequency, u - magnetic > permeability. > As you can see u can enhance (lower) skin depth big deal. Other approach is > to make r=0 (superconductor). > > Best regards, > > Alex Gourari, > > > > > -Original Message- > From: Ken Javor [mailto:ken.ja...@emccompliance.com] > Sent: Thursday, September 16, 2004 9:54 PM > To: emc-p...@ieee.org > Subject: Re: Germanium & ITO Window shielding effectiveness > > > What Mr. Mellberg says is narrowly true but interpreted broadly it causes > mischief. If a magnetic field is impinging upon a barrier at some distance > then Mr. Mellberg is correct. But if a shield can be arranged such that > eddy currents can be induced to flow, the magnetic field can be shorted out > using nothing but good conductivity - relative permeability identically > equal to unity. Hence the copper bands around transformers, and the > electrostatic shielding configuration for magnetic loops. Note that these > shields circumferentially surround the windings, but there is a narrow gap > so that the shield is not contiguous 360 degrees around the loop. These > shields are obviously not made of any ferrous metal, or more accurately, > they are made of high conductivity materials whose relative permeability is > again identically equal to unity, specifically so that they do not absorb > the field. But if the shield were 360 degrees contiguous, the field > penetrating the plane of the loop would cause eddy currents to flow in the > shield. By Lenz' Law, they would flow in a direction which would oppose the > field that caused them. Hence the net field within the loop would decrease, > with an attendant decrease in the potential output of the loop. That is > magnetic shielding by nonmagnetic materials. The mechanism is different > from a high permeability material. The mechanism is reflection, not > absorption. > >> From: "hansm" >> Date: Thu, 16 Sep 2004 14:30:13 -0700 >> To: "Gary McInturff" ,
Re: Germanium & ITO Window shielding effectiveness
Andrew, My firm has the technology to make optically transparent magnetic shield. Optical transparency is better than 65%. Costs relate to the requirement of how much field of view reduction of field Please contact me directly, off the group. - Robert - Robert A. Macy, PE. . m...@california.com 408 286 3985. . . . . . . fx 408 297 9121 AJM International Electronics Consultants 101 E San Fernando, Suite 402 San Jose, CA 95112 On Thu, 16 Sep 2004 08:21:12 +0100 "Price, Andrew P (UK Basildon)" wrote: > Hello group. > > Can anyone help with finding information on shielding > effectiveness of Germanium and ITO coated windows against > magnetic fields? > > Regards > Andy > > Andrew Price > Principal Development Engineer (EMC Specialist) > BAE SYSTEMS Avionics > A125 > Christopher Martin Road > Basildon, Essex > SS14 3EL > > tel: +44 (0) 1268 883308 > email: andrew.p.pr...@baesystems.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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Germanium & ITO Window shielding effectiveness
To get an idea of metal thickness consider that a CD is coated with 50-80 nanometers of aluminum or gold. You can see through it when you hold it up to a light source. 50 nm is one skin depth thick at 2 TeraHertz. Not much good for us. By the way, next time you get a CD you don't need place it in a microwave oven and run it for 3 seconds. Dave Cuthbert From: owner-emc-p...@listserv.ieee.org [mailto:owner-emc-p...@listserv.ieee.org] On Behalf Of Chris Maxwell Sent: Friday, September 17, 2004 7:11 AM To: John Woodgate; emc-p...@ieee.org Subject: RE: Germanium & ITO Window shielding effectiveness Whew, Everybody is on the beam. My two or three sentence reply has brought up a few questions. Let me just say that I take no exception to anybody debating me regarding electromagnetics...even though my surname is Maxwell. The genes have thinned out over a few generations; so I make many "debateable"...even "questionable"...or "wrong" judgements :-) For Mr Woodgate: Did I mean mu-metal? No, I meant monel. I put the question mark after it because I knew that it was available as a shielding material; but unsure of its permeability. According to Laird technologies website, monel contains Copper Iron and Tin. I assumed that the Iron would impart a permeability higher than 1. Will mu metal shield low frequency better than monel? Sure. But I haven't seen any mu-metal mesh screens for windows. I also don't know how expensive a mu metal mesh screen would be if you could get one. For Mr. Javor: 14 Ohms/square vs 14 Ohms /square inch... You're right, it's 14 Ohms/square. At what thikness of ITO? The usual thickness applied. I don't apply it; you would have to ask someone that applies it...for instance Chomerics (or whatever they are now called, these companies change names faster than I change beard styles). Will ITO provide some shielding? Sure 14 ohms/square will provide an impedance mismatch with air. You'll get some reflection of plane waves. But think about some of the other requirements of good shielding. A well shielded enclosure needs to treat seams and aperatures so that they won't radiate according to Babinet's principle. For instance, consider a metal enclosure with an ITO coated window. As surface currents flow on the enclosure, they will encounter the window. Most of the current will flow around the window, since the conductivity of the metal is orders of magnitude below the ITO. When the current flows around the window, you have charge acceleration (it changes direction)...which yields radiation. This is why I said ITO isn't so great for shielding. It provides some, but not much. Is 14ohms/square a higher conductivity than what's needed to dissipate static.? Sure you could dissipate static with a lower conductivity coating; but would it be as transparent as ITO? (Indium Tin Oxide by the way for readers who are wondering). That's why I consider ITO a good static dissipative coating. How about some tips from experience, since we've used ITO: 1. ITO can cause rings to appear on a window due to refraction (you know those little rainbow rings you see if you put a little oil or water between two pieces of glass). This isn't always a problem. It can happen if you sandwich an ITO coated window with another, or if you put an anti-glare coating on an ITO coated window. We had the anti-glare/ITO coating problem. Our display had little rainbow rings all over it. 1-a. See above. We once had the rainbow ring problem and had a bunch of windows we wanted to rework (i.e remove the ITO). The windows were lexan with ITO coating. We had to scrap the windows since we couldn't find a solvent that would remove the ITO while leaving the lexan intact. 2. ITO can be expensive, but any window shielding can be expensive. 3. ITO can be hard to bond to the bezel. 4. We were paying about 20-30 dollars for an ITO coated lexan window over a 8" display. Once we passed compliance testing, we went back to look at cost reductions. We tried a display windo with no ITO coating. Our results were just as good (this doesn't mean it didn't provide any shielding, it just means it didn't provide much; and the display wasn't a problem area). We were able to eliminate it and bring our window cost down to a few dollars. 5. ITO definitely has a low relative permeability; so it will have problems with absorbing magnetic fields. ITO definitely has a low conductivity, so it will have problems reflecting magnetic fields as well. (it won't readily form eddy currents) So, will ITO provide some magnetic shielding?...sure...but not much. To me, it falls into the category of a marginal fix. If you have a window that needs just a little bit of shielding to pass and you have no other option...then ITO is OK. However, if you need some serious shielding, you
RE: Germanium & ITO Window shielding effectiveness
Chris, A high permeability helps when the coating is thin- 1 skin depth or less. If the coating is much thicker than one skin depth then a non-magnetic conductor will be about as good as a magnetic conductor. If one has the depth, and the opening diameter is not too great (<1/2 wavelength), the waveguide beyond cutoff method works well. The waveguide length needs to be 3X the width. Dave Cuthbert Micron Technology From: owner-emc-p...@listserv.ieee.org mailto:owner-emc-p...@listserv.ieee.org] On Behalf Of Chris Maxwell Sent: Thursday, September 16, 2004 8:34 AM To: Price, Ed; emc-p...@ieee.org Subject: RE: Germanium & ITO Window shielding effectiveness Yeah, you're right. You need to consider the permeability.as well. I assumed that without saying so. Indium Tin Oxide doesn't have a very high permeability, if I remember correctly. It also doesn't have a high conductivity (as I mentioned earlier). So it seems to me that it's only good for dissipating static. Chris Maxwell From: owner-emc-p...@listserv.ieee.org mailto:owner-emc-p...@listserv.ieee.org] On Behalf Of Price, Ed Sent: Thursday, September 16, 2004 9:49 AM To: emc-p...@ieee.org Subject: RE: Germanium & ITO Window shielding effectiveness From: Chris Maxwell [mailto:chris.maxw...@nettest.com] Sent: Thursday, September 16, 2004 5:42 AM To: Barker, Neil; Price, Andrew P (UK Basildon); Emc-Pstc (E-mail) Subject: RE: Germanium & ITO Window shielding effectiveness I agree with Andy. ITO coating has a surface resistivity of 14Ohms/sq inch. You could probably get just as much surface resistivity from a coating of dust :-) ITO coatings are good at dissipating static; but I think that they are pretty much useless for shielding. I shudder to think of how naïve we were back in 1995 when this whole EMC (CE marking) kick began. We had one product with a window about 2" x 2". We had the window ITO coated. We spaced mounting screws every 1/2" around its edge and then used conductive RTV between the edge and the Aluminum panel into which it mounted. We took a $2 window assembly and turned it into a $50 window assembly. (we did this on the advice of someone we trusted) I looked into it a little while later and found the above facts regarding the surface resistivity of the ITO coating. We would have done just as much good by flushing money down the toilet. I would recommend a window with a fine, high mu wire (monel?) mesh shield. Tecknit and Chomerics make some shielded windows like this. Best regards, Chris Maxwell Umm first, what is ITO? (Indium Thorium Oxide , so maybe it also acts like a nightlight?) Sorry, couldn't help that. Anyway, we need to know the permeability of the material too; isn't it possible that even a fairly thin film of a poor conductivity, but permeable material, will give a bit of shielding (redirection) of a magnetic field? The OP was talking only about magnetic field shielding. Regards, Ed Ed Price ed.pr...@cubic.com WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 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/listserv/request/user-guide.html List rules:
Re: Germanium & ITO Window shielding effectiveness
ITO is commonly used to shield windows and anti-reflectance can be used to reduce glare. I suspect the rainbow is due to poor quality and not to all ITO coatings. The original patent holder of applying ITO to glass is Saleem Shaikh of Thin Film Devices in Anaheim. www.tfdinc.com. Copper tape is commonly used to ground the edges of the window with good results. Thin Film Devices can provide more information on thickness and shielding effectiveness if interested. They are a privately held applicator of these types of coatings. Regards, Steve Toyama 925 447-1200 From: "Chris Maxwell" To: "John Woodgate" ; Sent: Friday, September 17, 2004 6:10 AM Subject: RE: Germanium & ITO Window shielding effectiveness > Whew, > > Everybody is on the beam. > > My two or three sentence reply has brought up a few questions. Let me > just say that I take no exception to anybody debating me regarding > electromagnetics...even though my surname is Maxwell. The genes have > thinned out over a few generations; so I make many "debateable"...even > "questionable"...or "wrong" judgements :-) > > For Mr Woodgate: Did I mean mu-metal? > > No, I meant monel. I put the question mark after it because I knew > that it was available as a shielding material; but unsure of its > permeability. According to Laird technologies website, monel contains > Copper Iron and Tin. I assumed that the Iron would impart a > permeability higher than 1. > > Will mu metal shield low frequency better than monel? Sure. But I > haven't seen any mu-metal mesh screens for windows. I also don't know > how expensive a mu metal mesh screen would be if you could get one. > > For Mr. Javor: > > 14 Ohms/square vs 14 Ohms /square inch... You're right, it's 14 > Ohms/square. At what thikness of ITO? The usual thickness applied. I > don't apply it; you would have to ask someone that applies it...for > instance Chomerics (or whatever they are now called, these companies > change names faster than I change beard styles). > > Will ITO provide some shielding? Sure 14 ohms/square will provide an > impedance mismatch with air. You'll get some reflection of plane waves. > But think about some of the other requirements of good shielding. A > well shielded enclosure needs to treat seams and aperatures so that they > won't radiate according to Babinet's principle. For instance, consider > a metal enclosure with an ITO coated window. As surface currents flow > on the enclosure, they will encounter the window. Most of the current > will flow around the window, since the conductivity of the metal is > orders of magnitude below the ITO. When the current flows around the > window, you have charge acceleration (it changes direction)...which > yields radiation. This is why I said ITO isn't so great for shielding. > It provides some, but not much. > > Is 14ohms/square a higher conductivity than what's needed to dissipate > static.? Sure you could dissipate static with a lower conductivity > coating; but would it be as transparent as ITO? (Indium Tin Oxide by > the way for readers who are wondering). That's why I consider ITO a > good static dissipative coating. > > > How about some tips from experience, since we've used ITO: > > 1. ITO can cause rings to appear on a window due to refraction (you > know those little rainbow rings you see if you put a little oil or water > between two pieces of glass). This isn't always a problem. It can > happen if you sandwich an ITO coated window with another, or if you put > an anti-glare coating on an ITO coated window. We had the > anti-glare/ITO coating problem. Our display had little rainbow rings > all over it. > > > 1-a. See above. We once had the rainbow ring problem and had a bunch > of windows we wanted to rework (i.e remove the ITO). The windows were > lexan with ITO coating. We had to scrap the windows since we couldn't > find a solvent that would remove the ITO while leaving the lexan intact. > > > 2. ITO can be expensive, but any window shielding can be expensive. > > 3. ITO can be hard to bond to the bezel. > > 4. We were paying about 20-30 dollars for an ITO coated lexan window > over a 8" display. Once we passed compliance testing, we went back to > look at cost reductions. We tried a display windo with no ITO coating. > Our results were just as good (this doesn't mean it didn't provide any > shielding, it just means it didn't provide much; and the display wasn't > a problem area). We were able to eliminate it and bring our window cost > down to a few dollars. > > 5. ITO definitely has a low relative permea
RE: Germanium & ITO Window shielding effectiveness
Probably not enough to help out the permeability much. Too bad. From: owner-emc-p...@listserv.ieee.org [mailto:owner-emc-p...@listserv.ieee.org] On Behalf Of John Woodgate Sent: Friday, September 17, 2004 9:31 AM To: emc-p...@ieee.org Subject: Re: Germanium & ITO Window shielding effectiveness In article <39f7060a00b5e946b516261c077441c02ea...@utexch1w.gnnettest.co m>, Chris Maxwell writes >No, I meant monel. I put the question mark after it because I knew >that it was available as a shielding material; but unsure of its >permeability. According to Laird technologies website, monel contains >Copper Iron and Tin. I assumed that the Iron would impart a >permeability higher than 1. Fe 2% typical. The data sheets that I looked at don't even mention magnetic properties. -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Germanium & ITO Window shielding effectiveness
In article <39f7060a00b5e946b516261c077441c02ea...@utexch1w.gnnettest.co m>, Chris Maxwell writes >No, I meant monel. I put the question mark after it because I knew >that it was available as a shielding material; but unsure of its >permeability. According to Laird technologies website, monel contains >Copper Iron and Tin. I assumed that the Iron would impart a >permeability higher than 1. Fe 2% typical. The data sheets that I looked at don't even mention magnetic properties. -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Germanium & ITO Window shielding effectiveness
Whew, Everybody is on the beam. My two or three sentence reply has brought up a few questions. Let me just say that I take no exception to anybody debating me regarding electromagnetics...even though my surname is Maxwell. The genes have thinned out over a few generations; so I make many "debateable"...even "questionable"...or "wrong" judgements :-) For Mr Woodgate: Did I mean mu-metal? No, I meant monel. I put the question mark after it because I knew that it was available as a shielding material; but unsure of its permeability. According to Laird technologies website, monel contains Copper Iron and Tin. I assumed that the Iron would impart a permeability higher than 1. Will mu metal shield low frequency better than monel? Sure. But I haven't seen any mu-metal mesh screens for windows. I also don't know how expensive a mu metal mesh screen would be if you could get one. For Mr. Javor: 14 Ohms/square vs 14 Ohms /square inch... You're right, it's 14 Ohms/square. At what thikness of ITO? The usual thickness applied. I don't apply it; you would have to ask someone that applies it...for instance Chomerics (or whatever they are now called, these companies change names faster than I change beard styles). Will ITO provide some shielding? Sure 14 ohms/square will provide an impedance mismatch with air. You'll get some reflection of plane waves. But think about some of the other requirements of good shielding. A well shielded enclosure needs to treat seams and aperatures so that they won't radiate according to Babinet's principle. For instance, consider a metal enclosure with an ITO coated window. As surface currents flow on the enclosure, they will encounter the window. Most of the current will flow around the window, since the conductivity of the metal is orders of magnitude below the ITO. When the current flows around the window, you have charge acceleration (it changes direction)...which yields radiation. This is why I said ITO isn't so great for shielding. It provides some, but not much. Is 14ohms/square a higher conductivity than what's needed to dissipate static.? Sure you could dissipate static with a lower conductivity coating; but would it be as transparent as ITO? (Indium Tin Oxide by the way for readers who are wondering). That's why I consider ITO a good static dissipative coating. How about some tips from experience, since we've used ITO: 1. ITO can cause rings to appear on a window due to refraction (you know those little rainbow rings you see if you put a little oil or water between two pieces of glass). This isn't always a problem. It can happen if you sandwich an ITO coated window with another, or if you put an anti-glare coating on an ITO coated window. We had the anti-glare/ITO coating problem. Our display had little rainbow rings all over it. 1-a. See above. We once had the rainbow ring problem and had a bunch of windows we wanted to rework (i.e remove the ITO). The windows were lexan with ITO coating. We had to scrap the windows since we couldn't find a solvent that would remove the ITO while leaving the lexan intact. 2. ITO can be expensive, but any window shielding can be expensive. 3. ITO can be hard to bond to the bezel. 4. We were paying about 20-30 dollars for an ITO coated lexan window over a 8" display. Once we passed compliance testing, we went back to look at cost reductions. We tried a display windo with no ITO coating. Our results were just as good (this doesn't mean it didn't provide any shielding, it just means it didn't provide much; and the display wasn't a problem area). We were able to eliminate it and bring our window cost down to a few dollars. 5. ITO definitely has a low relative permeability; so it will have problems with absorbing magnetic fields. ITO definitely has a low conductivity, so it will have problems reflecting magnetic fields as well. (it won't readily form eddy currents) So, will ITO provide some magnetic shielding?...sure...but not much. To me, it falls into the category of a marginal fix. If you have a window that needs just a little bit of shielding to pass and you have no other option...then ITO is OK. However, if you need some serious shielding, you'll probably need to look at a wire mesh window insert. If you need some serious magnetic field shielding, then try to find a wire mesh window insert with a high permeability. Of course, these are just my own opinions. Chris Maxwell Nettest 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send m
RE: Germanium & ITO Window shielding effectiveness
Ken, Your approach about eddy currents somewhat true, but not all. We would never be in need of hign-mu materials then. You forget about skin effect that limits your shielding effectiveness. As long as can provide enough material thickness >> skin effect depth you are home free. Otherwise eddy currents in your shield will not compensate impinging magnetic flux fully. Look at the skin depth formula h = ((2*r)/(2*pi*f*u))^0.5 where r-resistivity (Ohm*in), f - impinging wave frequency, u - magnetic permeability. As you can see u can enhance (lower) skin depth big deal. Other approach is to make r=0 (superconductor). Best regards, Alex Gourari, From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Thursday, September 16, 2004 9:54 PM To: emc-p...@ieee.org Subject: Re: Germanium & ITO Window shielding effectiveness What Mr. Mellberg says is narrowly true but interpreted broadly it causes mischief. If a magnetic field is impinging upon a barrier at some distance then Mr. Mellberg is correct. But if a shield can be arranged such that eddy currents can be induced to flow, the magnetic field can be shorted out using nothing but good conductivity - relative permeability identically equal to unity. Hence the copper bands around transformers, and the electrostatic shielding configuration for magnetic loops. Note that these shields circumferentially surround the windings, but there is a narrow gap so that the shield is not contiguous 360 degrees around the loop. These shields are obviously not made of any ferrous metal, or more accurately, they are made of high conductivity materials whose relative permeability is again identically equal to unity, specifically so that they do not absorb the field. But if the shield were 360 degrees contiguous, the field penetrating the plane of the loop would cause eddy currents to flow in the shield. By Lenz' Law, they would flow in a direction which would oppose the field that caused them. Hence the net field within the loop would decrease, with an attendant decrease in the potential output of the loop. That is magnetic shielding by nonmagnetic materials. The mechanism is different >from a high permeability material. The mechanism is reflection, not absorption. > From: "hansm" > Date: Thu, 16 Sep 2004 14:30:13 -0700 > To: "Gary McInturff" , "'Price, Ed'" > , > Subject: Re: Germanium & ITO Window shielding effectiveness > > In order to attain eny significant mangentic shielding, at least Fe, Ni or > Co must be in the alloy. All other metals simply provide electric field > shielding which for low frequencies (long wavelengths), do not do much of H > field shielding. Thickness counts and can be reduced by increasing the > relative permeability at frequency of interest. Hence mu metals. > > Hans Mellberg > Engineering Manager > BACL, a TCB and an EU CAB > 230 Commercial Street > Sunnyvale CA 94085 USA > 408-732-9162 x38 > 408-732-9164 fax > > > 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/listserv/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > 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 > > 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help,
Re: Germanium & ITO Window shielding effectiveness
What Mr. Mellberg says is narrowly true but interpreted broadly it causes mischief. If a magnetic field is impinging upon a barrier at some distance then Mr. Mellberg is correct. But if a shield can be arranged such that eddy currents can be induced to flow, the magnetic field can be shorted out using nothing but good conductivity - relative permeability identically equal to unity. Hence the copper bands around transformers, and the electrostatic shielding configuration for magnetic loops. Note that these shields circumferentially surround the windings, but there is a narrow gap so that the shield is not contiguous 360 degrees around the loop. These shields are obviously not made of any ferrous metal, or more accurately, they are made of high conductivity materials whose relative permeability is again identically equal to unity, specifically so that they do not absorb the field. But if the shield were 360 degrees contiguous, the field penetrating the plane of the loop would cause eddy currents to flow in the shield. By Lenz' Law, they would flow in a direction which would oppose the field that caused them. Hence the net field within the loop would decrease, with an attendant decrease in the potential output of the loop. That is magnetic shielding by nonmagnetic materials. The mechanism is different >from a high permeability material. The mechanism is reflection, not absorption. > From: "hansm" > Date: Thu, 16 Sep 2004 14:30:13 -0700 > To: "Gary McInturff" , "'Price, Ed'" > , > Subject: Re: Germanium & ITO Window shielding effectiveness > > In order to attain eny significant mangentic shielding, at least Fe, Ni or > Co must be in the alloy. All other metals simply provide electric field > shielding which for low frequencies (long wavelengths), do not do much of H > field shielding. Thickness counts and can be reduced by increasing the > relative permeability at frequency of interest. Hence mu metals. > > Hans Mellberg > Engineering Manager > BACL, a TCB and an EU CAB > 230 Commercial Street > Sunnyvale CA 94085 USA > 408-732-9162 x38 > 408-732-9164 fax > > > 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/listserv/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > 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 > > 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Germanium & ITO Window shielding effectiveness
The usual disclaimer about an unwillingness to debate anyone surnamed Maxwell in the field of electromagnetics... I don't understand some of the statements and implications made in this exchange. 1) "ITO coating has a surface resistivity of 14Ohms/sq inch." First off, a nit, but per square inch is irrelevant, it is X Ohms per square. 2) "ITO coating has a surface resistivity of 14Ohms/sq inch." I think the resistivity would depend on the thickness of the deposited layer. A more correct statement would be, "ITO coating has a surface resistivity of 14Ohms/sq inch at a thickness of Y mils. 3) I am pretty sure ITO coatings are used as heaters for windshields/ windscreens. 14 Ohms per square is WAY more conductivity than necessary to dissipate static. I was warned that the conductive deposit Ford used a few years back on some passenger car models for instant windshield de-icing/ defogging would make a radar detector mounted behind the windshield useless. 4) Magnetic fields are by definition those whose field impedance is less than 377 Ohms. Basic Shelkunoff shielding theory says that the reflection portion of shielding is proportional to the mismatch between the wave impedance and the resistivity of the barrier. Clearly 14 Ohms per square is nowhere near as a good a mismatch as a metal enclosure, or a deposited metal coating on plastic, but it is not negligible if the impinging wave is close to far field in nature. > From: "Chris Maxwell" > Date: Thu, 16 Sep 2004 08:41:38 -0400 > To: "Barker, Neil" , "Price, Andrew P \(UK Basildon\)" > , "Emc-Pstc \(E-mail\)" > Subject: RE: Germanium & ITO Window shielding effectiveness > > I agree with Andy. > > ITO coating has a surface resistivity of 14Ohms/sq inch. You could probably > get just as much surface resistivity from a coating of dust :-) > > ITO coatings are good at dissipating static; but I think that they are pretty > much useless for shielding. > > I shudder to think of how naïve we were back in 1995 when this whole EMC (CE > marking) kick began. We had one product with a window about 2" x 2". We had > the window ITO coated. We spaced mounting screws every 1/2" around its edge > and then used conductive RTV between the edge and the Aluminum panel into > which it mounted. We took a $2 window assembly and turned it into a $50 > window assembly. (we did this on the advice of someone we trusted) I looked > into it a little while later and found the above facts regarding the surface > resistivity of the ITO coating. We would have done just as much good by > flushing money down the toilet. > > I would recommend a window with a fine, high mu wire (monel?) mesh shield. > Tecknit and Chomerics make some shielded windows like this. > > Best regards, > > Chris Maxwell > > -Original Message- > From: owner-emc-p...@listserv.ieee.org > [mailto:owner-emc-p...@listserv.ieee.org] On Behalf Of Barker, Neil > Sent: Thursday, September 16, 2004 3:44 AM > To: 'Price, Andrew P (UK Basildon)'; Emc-Pstc (E-mail) > Subject: RE: Germanium & ITO Window shielding effectiveness > > Andy, > > While I have no objective evidence on this subject, I would not expect > either of these to be particularly effective against magnetic fields as they > are both thin films of fairly high resistivity. I suspect that it could be > one of our products behind these windows, so is there any way that we can > help? > > Best regards, > > Neil R. Barker C.Eng. MIEE FSEE MIEEE > Manager > Compliance Engineering > e2v technologies (uk) ltd > 106 Waterhouse Lane > Chelmsford > Essex > CM1 2QU > UK > > Tel: +44 (0)1245 453616 > Fax: +44 (0)1245 453410 > e-mail: neil.bar...@e2v.com > Web: http://www.e2v.com > > > -Original Message- > From: Price, Andrew P (UK Basildon) > [mailto:andrew.p.pr...@baesystems.com] > Sent: 16 September 2004 08:21 > To: Emc-Pstc (E-mail) > Subject: Germanium & ITO Window shielding effectiveness > > > Hello group. > > Can anyone help with finding information on shielding effectiveness of > Germanium and ITO coated windows against magnetic fields? > > Regards > Andy > > Andrew Price > Principal Development Engineer (EMC Specialist) > BAE SYSTEMS Avionics > A125 > Christopher Martin Road > Basildon, Essex > SS14 3EL > > tel: +44 (0) 1268 883308 > email: andrew.p.pr...@baesystems.com > > > > This email and any attachments are confidential to the intended > recipient and may also be privileged. If you are not the intended > recipient please delete it from your system and notify the sender. >
Re: Germanium & ITO Window shielding effectiveness
In article <015001c49c34$5a0cfe90$5101a8c0@hanspc>, hansm writes >In order to attain eny significant mangentic shielding, at least Fe, Ni >or >Co must be in the alloy. Not necessarily; now there are ferromagnetic alloys containing rare- earth elements (lanthanides) but no Fe, Co or Ni. But think . -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Germanium & ITO Window shielding effectiveness
In article <39f7060a00b5e946b516261c077441c02ea...@utexch1w.gnnettest.co
m>, Chris Maxwell writes
>I would recommend a window with a fine, high mu wire (monel?) mesh
>shield. Tecknit and Chomerics make some shielded windows like this.
Monel (various grades, but typically Ni65/Cu33/Fe 2) is a corrosion-
resistant alloy. It appears not to have any special magnetic properties.
Perhaps you meant mu-metal ('Permalloy' etc.), a range of Ni/Fe alloys
that can have very high permeability.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
This message is from the IEEE Product Safety Engineering Society
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Re: Germanium & ITO Window shielding effectiveness
In order to attain eny significant mangentic shielding, at least Fe, Ni or Co must be in the alloy. All other metals simply provide electric field shielding which for low frequencies (long wavelengths), do not do much of H field shielding. Thickness counts and can be reduced by increasing the relative permeability at frequency of interest. Hence mu metals. Hans Mellberg Engineering Manager BACL, a TCB and an EU CAB 230 Commercial Street Sunnyvale CA 94085 USA 408-732-9162 x38 408-732-9164 fax 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Germanium & ITO Window shielding effectiveness
Depending on the enclosure material if its isn't' some high permeability material such as mu metal, the window probably isn't' the greatest concern to magnetic radiation is it? A quick but old example is putting a CRT on top of aluminum or steel CPU chassis over or near the power supplies large input transformers (long before switch mode supplies) used to cause a lot of deflection and 50/60 Hz interference. Either the monitor had to be moved or the CRT yoke magnetically shielded with mu metal. Gary From: Price, Ed [mailto:ed.pr...@cubic.com] Sent: Thursday, September 16, 2004 6:49 AM To: emc-p...@ieee.org Subject: RE: Germanium & ITO Window shielding effectiveness From: Chris Maxwell [mailto:chris.maxw...@nettest.com] Sent: Thursday, September 16, 2004 5:42 AM To: Barker, Neil; Price, Andrew P (UK Basildon); Emc-Pstc (E-mail) Subject: RE: Germanium & ITO Window shielding effectiveness I agree with Andy. ITO coating has a surface resistivity of 14Ohms/sq inch. You could probably get just as much surface resistivity from a coating of dust :-) ITO coatings are good at dissipating static; but I think that they are pretty much useless for shielding. I shudder to think of how naïve we were back in 1995 when this whole EMC (CE marking) kick began. We had one product with a window about 2" x 2". We had the window ITO coated. We spaced mounting screws every 1/2" around its edge and then used conductive RTV between the edge and the Aluminum panel into which it mounted. We took a $2 window assembly and turned it into a $50 window assembly. (we did this on the advice of someone we trusted) I looked into it a little while later and found the above facts regarding the surface resistivity of the ITO coating. We would have done just as much good by flushing money down the toilet. I would recommend a window with a fine, high mu wire (monel?) mesh shield. Tecknit and Chomerics make some shielded windows like this. Best regards, Chris Maxwell Umm first, what is ITO? (Indium Thorium Oxide , so maybe it also acts like a nightlight?) Sorry, couldn't help that. Anyway, we need to know the permeability of the material too; isn't it possible that even a fairly thin film of a poor conductivity, but permeable material, will give a bit of shielding (redirection) of a magnetic field? The OP was talking only about magnetic field shielding. Regards, Ed Ed Price ed.pr...@cubic.com WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Germanium & ITO Window shielding effectiveness
Yeah, you're right. You need to consider the permeability.as well. I assumed that without saying so. Indium Tin Oxide doesn't have a very high permeability, if I remember correctly. It also doesn't have a high conductivity (as I mentioned earlier). So it seems to me that it's only good for dissipating static. Chris Maxwell From: owner-emc-p...@listserv.ieee.org mailto:owner-emc-p...@listserv.ieee.org] On Behalf Of Price, Ed Sent: Thursday, September 16, 2004 9:49 AM To: emc-p...@ieee.org Subject: RE: Germanium & ITO Window shielding effectiveness From: Chris Maxwell [mailto:chris.maxw...@nettest.com] Sent: Thursday, September 16, 2004 5:42 AM To: Barker, Neil; Price, Andrew P (UK Basildon); Emc-Pstc (E-mail) Subject: RE: Germanium & ITO Window shielding effectiveness I agree with Andy. ITO coating has a surface resistivity of 14Ohms/sq inch. You could probably get just as much surface resistivity from a coating of dust :-) ITO coatings are good at dissipating static; but I think that they are pretty much useless for shielding. I shudder to think of how naïve we were back in 1995 when this whole EMC (CE marking) kick began. We had one product with a window about 2" x 2". We had the window ITO coated. We spaced mounting screws every 1/2" around its edge and then used conductive RTV between the edge and the Aluminum panel into which it mounted. We took a $2 window assembly and turned it into a $50 window assembly. (we did this on the advice of someone we trusted) I looked into it a little while later and found the above facts regarding the surface resistivity of the ITO coating. We would have done just as much good by flushing money down the toilet. I would recommend a window with a fine, high mu wire (monel?) mesh shield. Tecknit and Chomerics make some shielded windows like this. Best regards, Chris Maxwell Umm first, what is ITO? (Indium Thorium Oxide , so maybe it also acts like a nightlight?) Sorry, couldn't help that. Anyway, we need to know the permeability of the material too; isn't it possible that even a fairly thin film of a poor conductivity, but permeable material, will give a bit of shielding (redirection) of a magnetic field? The OP was talking only about magnetic field shielding. Regards, Ed Ed Price ed.pr...@cubic.com WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Germanium & ITO Window shielding effectiveness
From: Chris Maxwell [mailto:chris.maxw...@nettest.com] Sent: Thursday, September 16, 2004 5:42 AM To: Barker, Neil; Price, Andrew P (UK Basildon); Emc-Pstc (E-mail) Subject: RE: Germanium & ITO Window shielding effectiveness I agree with Andy. ITO coating has a surface resistivity of 14Ohms/sq inch. You could probably get just as much surface resistivity from a coating of dust :-) ITO coatings are good at dissipating static; but I think that they are pretty much useless for shielding. I shudder to think of how naïve we were back in 1995 when this whole EMC (CE marking) kick began. We had one product with a window about 2" x 2". We had the window ITO coated. We spaced mounting screws every 1/2" around its edge and then used conductive RTV between the edge and the Aluminum panel into which it mounted. We took a $2 window assembly and turned it into a $50 window assembly. (we did this on the advice of someone we trusted) I looked into it a little while later and found the above facts regarding the surface resistivity of the ITO coating. We would have done just as much good by flushing money down the toilet. I would recommend a window with a fine, high mu wire (monel?) mesh shield. Tecknit and Chomerics make some shielded windows like this. Best regards, Chris Maxwell Umm first, what is ITO? (Indium Thorium Oxide , so maybe it also acts like a nightlight?) Sorry, couldn't help that. Anyway, we need to know the permeability of the material too; isn't it possible that even a fairly thin film of a poor conductivity, but permeable material, will give a bit of shielding (redirection) of a magnetic field? The OP was talking only about magnetic field shielding. Regards, Ed Ed Price ed.pr...@cubic.com WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Germanium & ITO Window shielding effectiveness
I agree with Andy. ITO coating has a surface resistivity of 14Ohms/sq inch. You could probably get just as much surface resistivity from a coating of dust :-) ITO coatings are good at dissipating static; but I think that they are pretty much useless for shielding. I shudder to think of how naïve we were back in 1995 when this whole EMC (CE marking) kick began. We had one product with a window about 2" x 2". We had the window ITO coated. We spaced mounting screws every 1/2" around its edge and then used conductive RTV between the edge and the Aluminum panel into which it mounted. We took a $2 window assembly and turned it into a $50 window assembly. (we did this on the advice of someone we trusted) I looked into it a little while later and found the above facts regarding the surface resistivity of the ITO coating. We would have done just as much good by flushing money down the toilet. I would recommend a window with a fine, high mu wire (monel?) mesh shield. Tecknit and Chomerics make some shielded windows like this. Best regards, Chris Maxwell From: owner-emc-p...@listserv.ieee.org mailto:owner-emc-p...@listserv.ieee.org] On Behalf Of Barker, Neil Sent: Thursday, September 16, 2004 3:44 AM To: 'Price, Andrew P (UK Basildon)'; Emc-Pstc (E-mail) Subject: RE: Germanium & ITO Window shielding effectiveness Andy, While I have no objective evidence on this subject, I would not expect either of these to be particularly effective against magnetic fields as they are both thin films of fairly high resistivity. I suspect that it could be one of our products behind these windows, so is there any way that we can help? Best regards, Neil R. Barker C.Eng. MIEE FSEE MIEEE Manager Compliance Engineering e2v technologies (uk) ltd 106 Waterhouse Lane Chelmsford Essex CM1 2QU UK Tel: +44 (0)1245 453616 Fax: +44 (0)1245 453410 e-mail: neil.bar...@e2v.com Web: http://www.e2v.com From: Price, Andrew P (UK Basildon) [mailto:andrew.p.pr...@baesystems.com] Sent: 16 September 2004 08:21 To: Emc-Pstc (E-mail) Subject: Germanium & ITO Window shielding effectiveness Hello group. Can anyone help with finding information on shielding effectiveness of Germanium and ITO coated windows against magnetic fields? Regards Andy Andrew Price Principal Development Engineer (EMC Specialist) BAE SYSTEMS Avionics A125 Christopher Martin Road Basildon, Essex SS14 3EL tel: +44 (0) 1268 883308 email: andrew.p.pr...@baesystems.com This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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...@ie
RE: Germanium & ITO Window shielding effectiveness
Andy, While I have no objective evidence on this subject, I would not expect either of these to be particularly effective against magnetic fields as they are both thin films of fairly high resistivity. I suspect that it could be one of our products behind these windows, so is there any way that we can help? Best regards, Neil R. Barker C.Eng. MIEE FSEE MIEEE Manager Compliance Engineering e2v technologies (uk) ltd 106 Waterhouse Lane Chelmsford Essex CM1 2QU UK Tel: +44 (0)1245 453616 Fax: +44 (0)1245 453410 e-mail: neil.bar...@e2v.com Web: http://www.e2v.com From: Price, Andrew P (UK Basildon) [mailto:andrew.p.pr...@baesystems.com] Sent: 16 September 2004 08:21 To: Emc-Pstc (E-mail) Subject: Germanium & ITO Window shielding effectiveness Hello group. Can anyone help with finding information on shielding effectiveness of Germanium and ITO coated windows against magnetic fields? Regards Andy Andrew Price Principal Development Engineer (EMC Specialist) BAE SYSTEMS Avionics A125 Christopher Martin Road Basildon, Essex SS14 3EL tel: +44 (0) 1268 883308 email: andrew.p.pr...@baesystems.com This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Germanium & ITO Window shielding effectiveness
Hello group. Can anyone help with finding information on shielding effectiveness of Germanium and ITO coated windows against magnetic fields? Regards Andy Andrew Price Principal Development Engineer (EMC Specialist) BAE SYSTEMS Avionics A125 Christopher Martin Road Basildon, Essex SS14 3EL tel: +44 (0) 1268 883308 email: andrew.p.pr...@baesystems.com This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
