Yes, Gert, there is a fine line. The alarm systems standards are written around performance. It would be highly unlikely that the failure of a CCTV camera to comply with the increased immunity standards would create a physical hazard from the camera itself. Rather, failure of the camera to perform as intented might result in an hazard caused by external conditions that occur undetected (e.g., fire, robbery, intrusion, etc).
Richard Woods Sensormatic Electronics Tyco International -----Original Message----- From: CE-TEST [mailto:cet...@cetest.nl] Sent: Monday, January 07, 2002 9:13 AM To: richwo...@tycoint.com; emc-p...@majordomo.ieee.org Subject: RE: EMC-related safety issues Hi Richard, Group I agree that those requirements look safety related, but they are strictly functional. The difference is subtle: As this standard is concerned with equipment used for safety purposes, the requirements are thus safety related in THAT sense, but not in the sense of equipment's safety or safety risks CAUSED by using the equipment. These are not considered, althouigh testin according to EN 50130 may contribute to increased product safety. Most safety topics can be found in LVD related standards, such as EN 60730 (not for EN 50130 equipment). Many LVD standards are not very elaborate about EM Safety, and directly point to a deviation of the Generic standards. I might say that "EM and safety of equipment" is an area that is completely unexplored. (i do not use the abbreviation EMC as this topic is not about compatibility. I should use EMS (afety) but this abbreviation has already been taken...) Gert Gremmen -----Original Message----- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of richwo...@tycoint.com Sent: maandag 7 januari 2002 14:13 To: emc-p...@majordomo.ieee.org Subject: RE: EMC-related safety issues John, I have to disagree with your statement, "As far as CENELEC is concerned, it was a conscious decision not to incorporate 'EMC and Safety' issues into EMC standards, but to treat it as a separate subject." If this is true, how do you explain the fact that the Alarm Systems immunity standard EN 50130-4 requires a higher immunity levels and that, per clause 6, the acceptance criteria is per the requirements of a CENELEC performance standard if it is published - e.g. EN 50132-2-1 (CCTV cameras), EN50132-4-1 (Access Control). This certainly appears to be safety related. Richard Woods Sensormatic Electronics Tyco International -----Original Message----- From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Friday, January 04, 2002 11:49 AM To: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues I read in !emc-pstc that cherryclo...@aol.com wrote (in <167.698dddc.296 70...@aol.com>) about 'EMC-related safety issues', on Fri, 4 Jan 2002: > As my paper at the IEEE's EMC Symposium in Montreal and my recent article in > ITEM UPDATE 2001 show - at present EMC standards don't address safety > issues, and most safety standards don't address EMC-related functional > safety issues. As far as CENELEC is concerned, it was a conscious decision not to incorporate 'EMC and Safety' issues into EMC standards, but to treat it as a separate subject. Some people may find a clarification helpful. We have EMC matters, concerned with compatibility between items of equipment, ensuring that they continue to work (Criterion A in the Generic Standards) or fail gracefully (Criteria B and C). These criteria do not address safety issues, as indicated in paragraph 1 above. However, the Generic Standards do have a limited 'blanket' requirement, that equipment must not become unsafe *during testing*. We also have safety matters per se, which don't involve EMC. We ALSO have the separate subject, called 'EMC and Safety' or reasonable variants thereof. This addresses the matter of equipment becoming unsafe *in service* due to excessive emission levels in the environment, or lack of sufficient immunity to acceptable emission levels. So far, this seems perfectly reasonable. BUT it stops seeming reasonable when the question 'What could go wrong?' is asked and statistical data is used to attempt to answer it. To take a very simple example (maybe over-simplified), we might say that the probability of an unsafe occurrence should be less than 10^-9. That immediately means that the designer of the equipment has to look at ALL risk scenarios down to the billion-to-one against level of probability. To say that that is difficult is surely a great understatement. But some experts in the field seem to ignore that great difficulty, and simply (or maybe not so simply) state that if the designer fails to take into account ANY scenario that subsequently results in an unsafe condition, the designer has failed in his professional responsibility, and may be held criminally responsible for negligence. Well, let us be very circumspect designers and look at what immunity levels we might need to get down to that 10^-9 probability. For radiated emissions, the necessary test levels seem to be of the order of 100 V/m. Test levels for other disturbances seem to be equally distantly related to the levels normally experienced and to the test levels in pure EMC standards. We might conclude that assessment of EMC immunity per se is completely unnecessary, because testing for 'EMC and Safety' requires test levels of the order of 30 dB higher! One could go, with the sort of reasoning advocated by some experts, further into the realms of fantasy. Suppose, for a particular piece of equipment, the designer, with great diligence, identifies a million threat scenarios, each of which has a probability of 10^-9. The cumulative probability of ANY ONE of them occurring is only 10^-3. Bit risky, that! If the above reasoning seems flawed, consider a specific case, a lottery with 2000 tickets, numbered 0000 to 1999. One person can buy up to 5 tickets, and all tickets are sold. Consider the probability of a 'remarkable occurrence'. This might be the drawing of the number '0000' or '1111' or '1234' or even '1010', depending on what you think is 'remarkable'. OK, we already have a cumulative probability down from 1 in 2000 to 1 in 667 or 1 in 500. Now add in the probability that a participant in the lottery is chosen at random to draw the winning number, and draws (one of) his or her own numbers ...... You shouldn't be able to get very long odds on a 'remarkable occurrence'! -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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