Dear Ken Any electromagnetic emissions, whether conducted or radiated, including spurious emissions (however you wish to define the word 'spurious') can be demodulated by the non-linear processes in semiconductors, vacuum tubes, and the like. So the spread of possible problems goes beyond merely preventing the reception of radio communications.
I didn't catch the previous correspondence on this issue, but it seems to me that a very narrow definition of the word 'intrinsic' is being used - and this could be misconstrued by some engineers (or their managers) who are more semantically challenged and possibly lead to possible safety hazards for the users of their products or systems, or third parties. Regards, Keith Armstrong www.cherryclough.com In a message dated 31/12/01 15:46:21 GMT Standard Time, ken.ja...@emccompliance.com writes: > Subj:Re: EMC-related safety issues > Date:31/12/01 15:46:21 GMT Standard Time > From: ken.ja...@emccompliance.com (Ken Javor) > Sender: owner-emc-p...@majordomo.ieee.org > Reply-to: <A > HREF="mailto:ken.ja...@emccompliance.com";>ken.ja...@emccompliance.com</A> > (Ken Javor) > To: cherryclo...@aol.com, emc-p...@majordomo.ieee.org > > All of this message is very interesting and I have no problem with it at > all. That doesn't change the fact that, as I and others stated earlier, > there is no intrinsic safety issue with a spurious emission. Spurious > emissions only affect the ability to receive a radio signal. That was and > is the only issue. The fact that sometimes reception of that radio signal > is safety-critical is another matter entirely. > > ---------- > From: cherryclo...@aol.com > To: emc-p...@majordomo.ieee.org > Subject: EMC-related safety issues > Date: Mon, Dec 31, 2001, 7:12 AM > > > >> Dear all >> There was a discussion about electromagnetic emissions and safety issues a >> couple of weeks ago which I only caught the tail end of, so I hope my >> comments below are relevant and useful. >> I would also like to make a plea for assistance. >> >> Spurious emissions and safety. >> Even if we ignore 'leakages' from intentional transmitters and industrial >> RF processing equipment (such as dielectric heaters) and also ignore >> biological (human health) hazards, it is quite clear that spurious >> emissions can increase the risks of some safety hazards. >> >> I have worked on problems where spurious emissions from >> microprocessor-based systems were interfering with safety-related radio >> communications, and also on a pulsed-laser welder that interfered with >> helicopter air traffic control radio communications. The laser could only >> be operated when the nearby airport was closed to helicopters during the >> night. >> >> Section 7 of the 'core' of the IEE's professional guidance document on >> 'EMC and Functional Safety' includes an example of a airplane passenger's >> laptop significantly affecting the pilot's compass reading. You can >> download this useful guide for free from >> www.iee.org.uk/Policy/Areas/Electro (note: this URL may be case >> sensitive). >> >> Another useful source of interference anecdotes is the "Banana Skins" >> column in the EMC and Compliance Journal, which may be read at >> www.compliance-club.com. The two most recent issues are 'live' on the site >> and the others can be read by searching its archives. >> >> The IEE's Guide on EMC and Functional Safety. >> This guide adopts much the same approach to dealing with EMC-related >> safety issues as IEC/TS 61000-1-2:2001 "Electromagnetic Compatibility >> (EMC) - Part1-2: General - Methodology for the achievement of the >> functional safety of electrical and electronic equipment with regard to >> electromagnetic phenomena". >> (A key member of the IEC 61000-1-2 committee is a very senior safety >> expert and also a key member of the IEE Working Group that created this >> guide - helping to ensure compatibility between the two documents.) >> I understand that - after any modifications found necessary during its >> trial period - IEC/TS 61000-1-2 will probably become harmonised under the >> Low Voltage and Machinery safety directives. >> >> The IEE's guide on EMC and Functional Safety has been published for 18 >> months and downloaded by many thousands of professionals. I chaired a >> well-attended one-day seminar on it in London UK in February 2001 and >> presented a well-attended paper on it at the IEEE EMC International EMC >> Symposium in Montreal Canada last August (pages 774-779 in Volume 2 of the >> Proceedings). A number of articles about this IEE guide and the issues >> associated with EMC-related functional safety have appeared during 2000 >> and 2001 in international trade journals, most recently in ITEM UPDATE >> 2001 (pages 52-59). >> >> The IEE has received many congratulations on this guide but so far has >> received no negative comments or suggestions for improvement - but of >> course it is far from perfect and the WG that wrote it expects to update >> and improve it during 2002 and 2003. >> >> All suggestions for corrections, additions, or improvements from emc-pstc >> members or anyone else are most welcome. If you don't want to share your >> input with the whole emc-pstc group please send it to me directly at >> keith.armstr...@cherryclough.com or cherryclo...@aol.com, or else send >> them directly to Robert Croll in the Policy Division of the IEE: >> rjecr...@iee.org.uk. >> >> Many thanks! >> >> Finally, I wish you all a wonderful 2002! >> >> Keith Armstrong >> Cherry Clough Consultants >> http://www.cherryclough.com >>
