I too have found that to be the case, namely that the analogue circuits play a greater role in EMC immunity than the digital .
Ralph McDiarmid, AScT Compliance Engineering Group Xantrex Technology Inc From: [email protected] [mailto:[email protected]] On Behalf Of ce-test, qualified testing bv - Gert Gremmen Sent: Monday, August 24, 2009 11:48 AM To: Kunde, Brian; [email protected] Subject: RE: Ring Of Fire? Cell Phone Turns On Oven - Popcorn II? I have done quite a bit of digital equipment testing, and I have not often see a microprocessor being susceptible in the 10-20-30 V/m range. And yes cellphones above 1-2 Watts can easily generate 20-40 volts/m when emitting max power. What causes the problem in many cases is the analog circuitry associated with microprocessors: - scanned keyboards - supply voltage monitoring circuits - analog inputs (like temperature sensors) Where I would give the first category a big chance of having caused the problems. The problem is that digital designers do not uncommonly no nothing about: - current flowing through ground - current flowing in loops - other voltages then 1 and 0 - other signals then wanted signals Working at companies that: - do not think about their responsibilities unless penalized - focus on maximizing revenues and lowering costs - minimize on test costs "judged" superfluous ("because we never had any problem" , sounds familiar?) These companies are managed by "managers" that focus on: - Lowering the costs of education "hardware" - Maximizing their personal revenues - Minimizing their personnel revenues Digital designers are educated by schools that prefer: - Simulating electronics instead of experimenting - Simulating instead of soldering - Checking functional specifications only Which are managed by modern managers (ex bank?) that focus on: - Lowering the costs of education "hardware" - Maximizing their personal revenues - Minimizing their personnel revenues The lists above are in no way: - complete - objective - conclusive So don't judge the good old microprocessor and blame the managers ! ;<)) Gert Gremmen Ce-test Van: [email protected] [mailto:[email protected]] Namens Kunde, Brian Verzonden: maandag 24 augustus 2009 20:24 Aan: [email protected] Onderwerp: RE: Ring Of Fire? Cell Phone Turns On Oven - Popcorn II? Can anyone confirm that a cell phone can generate 10V/m or more at any reasonable distance? [lets say 1 meter]. I didn't think the transmitter was that powerful. We played around with a cell phone and our isotropic probe and we couldn't get a reading over a few V/m unless we put the phone right up against the antenna cone. And then, the maximum we read was around 30V/m, but again, that was with the phone touching the antenna of the probe. Curious. The Other Brian From: [email protected] [mailto:[email protected]] On Behalf Of John McAuley Sent: Monday, August 24, 2009 12:11 PM To: 'John Woodgate'; [email protected] Subject: RE: Ring Of Fire? Cell Phone Turns On Oven - Popcorn II? It was me, I thought I was replying to all. John McAuley DISCLAIMER: The information contained in this e-mail may be confidential and is intended solely for the use of the named addressee. Access, copying or re-use of the e-mail or any information contained therein by any other person is not authorised. If you are not the intended recipient please notify us immediately by returning the e-mail to the originator From: [email protected] [mailto:[email protected]] On Behalf Of John Woodgate Sent: 24 August 2009 16:33 To: [email protected] Subject: Re: Ring Of Fire? Cell Phone Turns On Oven - Popcorn II? In message <9d04b979323dcd428297dda95108893e0287f...@bb-corp-ex2.corp.cubic.cub>, dated Mon, 24 Aug 2009, "Price, Edward" <[email protected]> writes: >OTOH, I would expect to see 5 to 10 V/M at two meters distance from a >cell phone, so at a half-meter or less, I would be surprised to NOT see >some interaction. > >And then, on yet another hand, proximity of cell phones should be >expected for household systems. It was pointed out to me in a private email (why not to the list I don't know) that the relevant IEC/EN safety standard IEC 60335-1, applying to all household appliances, imposes in clause 19.11.4 'EMC for functional safety' requirements beyond those of CISPR 14-2, including an RF immunity test at 10 V/m (but you need to refer to yet another standard, IEC/EN 61000-4-3, to find the actual figure!). -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Things can always get better. But that's not the only option. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. 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