Yes indeed. The question of limits may reduce to WHERE [a device] must perform its function. If the only exceptional circumstance is a railway crossing or station platform, perhaps the limit need not be raised at all. That's what I thought when I saw the paper, anyway. U.S. firms and marketers, meanwhile, have for consumer devices only a ONE V/m *voluntary* immunity to contend with/ignore. Cheers, Cortland Richmond KA5S
----- Original Message ----- From: Ken Javor <mailto:ken.ja...@emccompliance.com> To: Untitled <mailto:emc-p...@ieee.org> Sent: 11/2/2009 8:57:25 AM Subject: Re: Where does 3V/m & 10V/m in RI come from? As Mr. Woodgate has been tirelessly pointing out, the limits are set to minimize complaints, but also cost. And safety isn’t an issue. If a medical device must wok anywhere under any circumstances, then it is like the safety-critical features of an automobile and the limits must go WAY up. Ken Javor Phone: (256) 650-5261 ________________________________ From: Cortland Richmond <k...@earthlink.net> Reply-To: <k...@earthlink.net> Date: Mon, 2 Nov 2009 08:40:31 -0500 To: <emc-p...@ieee.org> Subject: RE: Where does 3V/m & 10V/m in RI come from? How old is the 3V/m,10V/m requirement? It was, what, 25 years ago?, the FCC and EPA here surveyed fields in Spokane, Washington, and concluded that levels in the AM broadcast band were not a threat to health (never mind arcs >from ungrounded metal structures) at ~600 V/m. But would a AED work there? I've seen a paper regarding AED malfunction due to 16.67 Hz fields under overheard railway power in continental Europe. Is the standard immunity level really sufficient? Cortland Richmond KA5S ----- Original Message ----- From: Haynes, Tim (SELEX GALILEO, UK) <mailto:tim.hay...@selexgalileo.com> <mailto:tim.hay...@selexgalileo.com> To: emc-p...@ieee.org Sent: 11/2/2009 4:52:33 AM Subject: RE: Where does 3V/m & 10V/m in RI come from? Dear All, Where does 3V/m come from? I do not know but if I run some numbers? E(dBV/m)=P(dbW)+14.77+G+20log(1/Distance) How close would you put a 10kW transmitter to housing? 300m? what antenna gain? 6dB? E=40+14.77+6+20log(1/300) E=60.77-49.5 = 11.27 dBV/m =3.66V/m Try some other realistic examples then take a „view‰ on what number you would set as an immunity limit. There will be some occasions where 3V/m is too low but do you! make all equipment meet higher levels or do you set levels that satisfies most situations most of the time? Remember, most of the equipment that these limits apply to are semi permanent as far as their location is concerned. Somebody in the thread mentioned cars. Now cars are different. EMC tests (as per standards) can NEVER be used for safety certification as the tests do not simulate the „real world‰, either in maximum potential exposure levels, not in terms of the multiple exposures that can occur. If you want more on this, take a look at Keith Armstrong‚s presentation at http://www.theiet.org/events/2009/dig sts/emcuk/armstrong-vehicles.cfm?type=pdf Regards Tim ************************ Tim Haynes A1N10 Electromagnet ic Engineering Specialist SELEX Sensors and Airborne Systems 300 Capability Green Luton LU1 3PG ( Tel : +44 (0)1582 886239 7 Fax : +44 (0)1582 795863 ) Mob : +44 (0)7703 559 310 * E-mail : tim.hay...@selexgalileo.com P Please consider the environment before printing this email. There are 10 types of people in the world-those who understand binary and those who don't. J. Paxman ________________________________ SELEX Sensors and Airborne Systems Limited Registered Office: Sigma House, Christopher Martin Road, Basildon, Essex SS14 3EL A company registered in England & Wales. Company no. 02426132 ******************************************************************** This email and any attachments are confidential to the intended recipient and may also be privileged. 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