Re: duty cycle closure
No. You aren't applying the rule correctly. As I stated earlier: log a*b = log a + log b log b^n = n log b Combining, it is clear that log (a*b^n) = log a + n log b. -- From: umbdenst...@sensormatic.com To: emc-p...@majordomo.ieee.org, dmck...@corp.auspex.com Subject: duty cycle closure Date: Fri, Oct 19, 2001, 2:33 PM Going back to fundamentals -- Given a = duty cycle = average power and define ^2 = squared Then P[ave] = a P[ref] P = V^2/R V[ave]^2/R = aV[ref]^2/R, the Rs cancel leaving V[ave]^2 = aV[ref]^2 10 log(V[ave]^2) = 10 log (aV[ref]^2), which is equivalent to 20 log (V[ave]) = 20 log (aV[ref]) = 20 log (a) + 20 log (V[ref]) In the last equation one sees the duty cycle isolated as 20 log (a) when referring to power in terms of voltage. Best regards, Don Umbdenstock Sensormatic -- From: Doug McKean[SMTP:dmck...@corp.auspex.com] Reply To: Doug McKean Sent: Friday, October 19, 2001 2:41 PM To: emc-p...@majordomo.ieee.org Subject: Re: Is This Right? More to the proof discussion launched by the duty cycle question, given dB = 10 log (P1/P2) Let a be the duty cycle ratio, with 0a1, so that P1 = aP2. Then dB = 10 log (aP2/P2) = 10 log (a). Eq. (1) If 10 log (P1/P2) = 10 log (V1^2/V2^2) = 10 log (V1/V2)^2 = 20 log (V1/V2), Then does it follow that, dB = 10 log (aV2^2/V2^2) = 10 log (aV2/V2)^2 = 20 log (a) ? Eq. (2) If this is true, then duty cycle a = 10 log (a) from Eq. (1) and = 20 log (a) from Eq. (2) What am I missing? The original intention of the calculations. The first relation, dB = 10 log (aP2/P2) = 10 log (a) is a power relation. The second relation, dB = 10 log (aV2^2/V2^2) = 20 log (a) is a voltage relation. Equating the two is invalid since you're trying to equate two different concepts. Doesn't mean anything. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: Light Emission from Professional Photography Flashes
Hi Peter: Any limitations/requirements for amount of light emitted from professional photography flashes? Any UL, IEC or European standards which specify limitations? I know how many you like being photographed - but imagine what harm one of these flashes can cause to your eyes! The root question is what is the maximum safe optical energy as a function of time for the eye? I suspect there are many research documents for this eye parameter. Check out this optical radiation safety calculator: http://vision.arc.nasa.gov/personnel/jbm/home/exps/java/safe_txt.html The calculator is described for situations such as when the eye is illuminated for photography. I suspect this is for steady- state and not for flash. But, it should provide some references. Good luck, and best regards, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
duty cycle closure
Going back to fundamentals -- Given a = duty cycle = average power and define ^2 = squared Then P[ave] = a P[ref] P = V^2/R V[ave]^2/R = aV[ref]^2/R, the Rs cancel leaving V[ave]^2 = aV[ref]^2 10 log(V[ave]^2) = 10 log (aV[ref]^2), which is equivalent to 20 log (V[ave]) = 20 log (aV[ref]) = 20 log (a) + 20 log (V[ref]) In the last equation one sees the duty cycle isolated as 20 log (a) when referring to power in terms of voltage. Best regards, Don Umbdenstock Sensormatic -- From: Doug McKean[SMTP:dmck...@corp.auspex.com] Reply To: Doug McKean Sent: Friday, October 19, 2001 2:41 PM To: emc-p...@majordomo.ieee.org Subject: Re: Is This Right? More to the proof discussion launched by the duty cycle question, given dB = 10 log (P1/P2) Let a be the duty cycle ratio, with 0a1, so that P1 = aP2. Then dB = 10 log (aP2/P2) = 10 log (a). Eq. (1) If 10 log (P1/P2) = 10 log (V1^2/V2^2) = 10 log (V1/V2)^2 = 20 log (V1/V2), Then does it follow that, dB = 10 log (aV2^2/V2^2) = 10 log (aV2/V2)^2 = 20 log (a) ? Eq. (2) If this is true, then duty cycle a = 10 log (a) from Eq. (1) and = 20 log (a) from Eq. (2) What am I missing? The original intention of the calculations. The first relation, dB = 10 log (aP2/P2) = 10 log (a) is a power relation. The second relation, dB = 10 log (aV2^2/V2^2) = 20 log (a) is a voltage relation. Equating the two is invalid since you're trying to equate two different concepts. Doesn't mean anything. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: Is This Right?
More to the proof discussion launched by the duty cycle question, given dB = 10 log (P1/P2) Let a be the duty cycle ratio, with 0a1, so that P1 = aP2. Then dB = 10 log (aP2/P2) = 10 log (a). Eq. (1) If 10 log (P1/P2) = 10 log (V1^2/V2^2) = 10 log (V1/V2)^2 = 20 log (V1/V2), Then does it follow that, dB = 10 log (aV2^2/V2^2) = 10 log (aV2/V2)^2 = 20 log (a) ? Eq. (2) If this is true, then duty cycle a = 10 log (a) from Eq. (1) and = 20 log (a) from Eq. (2) What am I missing? The original intention of the calculations. The first relation, dB = 10 log (aP2/P2) = 10 log (a) is a power relation. The second relation, dB = 10 log (aV2^2/V2^2) = 20 log (a) is a voltage relation. Equating the two is invalid since you're trying to equate two different concepts. Doesn't mean anything. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: Light Emission from Professional Photography Flashes
If there aren't standards there probably should be. I remember seeing a NOVA episode in which Dr. Harold Edgerton, inventor of the strobe, demonstrated a strobe similar to that used during WWII to photograph German positions from the air at night. He fired the strobe at a newspaper 3 feet away and it instantly burst into flames! Makes the little green dot in front of your eye seem pretty trivial. Dan -Original Message- From: Peter Merguerian [mailto:pmerguer...@itl.co.il] Sent: Friday, October 19, 2001 11:46 AM To: EMC-PSTC (E-mail) Subject: Light Emission from Professional Photography Flashes Dear All, Any limitations/requirements for amount of light emitted from professional photography flashes? Any UL, IEC or European standards which specify limitations? I know how many you like being photographed - but imagine what harm one of these flashes can cause to your eyes! This e-mail message may contain privileged or confidential information. If you are not the intended recipient, you may not disclose, use, disseminate, distribute, copy or rely upon this message or attachment in any way. If you received this e-mail message in error, please return by forwarding the message and its attachments to the sender. PETER S. MERGUERIAN Technical Director I.T.L. (Product Testing) Ltd. 26 Hacharoshet St., POB 211 Or Yehuda 60251, Israel Tel: + 972-(0)3-5339022 Fax: + 972-(0)3-5339019 Mobile: + 972-(0)54-838175 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: high temperature circuit breaker
Neither endorsing or rejecting these breakers I just happen to be doing a little research of my own and have a spec sheet open in front of me on these things. Square D has a Multi-9 series of breakers that shows an operating temperature of -30 to -70 C. and tropical treatment 2 for 95% rh of 95% at 55C. I haven't looked any further to see if they are Listed/Certified to those temperatures or if those are just the marketing numbers so you'll want to follow-up on that. They have a wider range of amperage ratings than the others I have quickly reviewed. I happen to be looking at a 2 amp breaker and typically those have only been Listed for Supplemental Protectors rather than Branch Circuit protection. You also want to consider whether they are thermal or magnetic breakers. If your worried about high temperatures you probably want to look at the magnetic breakers because they are less heat sensitive. Here is a link http://www.squared.com/us/products/circuit_breakers.nsf/unid/B7E8BB545346010 D85256AA30051A705/$file/multi9ul489breakersFrameset.htm Good luck Gary -Original Message- From: kristiaan.carpent...@alcatel.be [mailto:kristiaan.carpent...@alcatel.be] Sent: Friday, October 19, 2001 7:24 AM To: emc-p...@majordomo.ieee.org Subject: high temperature circuitbreaker Hello group, Circuit breakers and residual current operated circuitbreakers for house-hold applications are typically cetified at 40 degree Celcius. If these types are built into other products, they do not comply with their temperature rating as specified in the safety certificate. Does any-one know about references to circuit-breakers(230V ac, 10A) that can work safely at higher temperatures (70...90 degrees) Regards, Kris Carpentier --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: 60601-1-2
For the latest developments on CENELEC (EN) standards you can go directly to their website search and just type in the standard number in the Standard reference field (http://www.cenelec.org/BASIS/celis/free/project/SF). Nick Momcilovic Product Safety Coordinator QTI N64W23110 Main Street Sussex, WI 53089-5301 USA Phone: +1-414-566-7915 Fax: +1-262-246-5376 mailto:nick.momcilo...@qtiworld.com http://www.qtiworld.com -Original Message- From: rehel...@mmm.com [mailto:rehel...@mmm.com] Sent: Friday, October 19, 2001 9:31 AM To: emc-p...@majordomo.ieee.org Subject: 60601-1-2 I heard that the IEC has issued the new 60601-1-2 EMC standard for medical equipment on the 30th of September. Does anyone know when the EN will follow and when its DOW will be? Thanks, Bob Heller 3M Product Safety, 76-1-01 St. Paul, MN 55107-1208 Tel: 651- 778-6336 Fax: 651-778-6252 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
Corrected text Re: What is minimum dBA measured difference above ambient noise for pulsing alarm.
Folks, It was pointed out that my quote from SEMI S2-0200e is incorrect. I would like to restate my question to include the correction. I apologize for any inconvenience my error has caused. My corrected question is as follows. . Can anyone cite a reference document / standard that determines if there is a minimum dBA sound level variation above an expected ambient environment that is suitable for a pulsing alarm. In my review , I have found that SEMI S2-0200E Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment states in Para. 27.1 ...Equipment should be designed to control exposures to sound pressure levels equal to or greater than 80 dBA continuous or intermittent sound pressure level, and 120 dB instantaneous (impulse) sound pressure level. Further, 29 CFR 1910.95 Occupational noise exposure states . 2.) If the variations in noise level involve maxima at intervals of 1 second or less, it is to be considered continuous. Are there any industry standards that recommends a pulse level variation? Your input on this subject is greatly appreciated. Best Regards,Paul J Smith Teradyne, Inc., Boston, MA 02111 paul.j.sm...@teradyne.com Voice 617-422-2997 Fax 603-843-7526 Paul J Smith 10/19/2001 09:56 AM To: SEHS Grapevine s...@semi.org, emc-p...@majordomo.ieee.org cc: Subject: Re: What is minimum dBA measured difference above ambient noise for pulsing alarm. (Document link: Paul J Smith) Folks, Can anyone cite a reference document / standard that determines if there is a minimum dBA sound level variation above an expected ambient environment that is suitable for a pulsing alarm. In my review , I have found that SEMI S2-0200E Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment states in Para. 27.1 ...Equipment should be designed to control exposures to sound pressure levels equal to or greater than sound pressure levels equal to or greater than 80 dBA continuous or intermittent sound pressure level, and 120 dB instantaneous (impulse) sound pressure level. Further, 29 CFR 1910.95 Occupational noise exposure states 2.) If the variations in noise level involve maxima at intervals of 1 second or less, it is to be considered continuous. Are there any industry standards that recommends a pulse level variation? Your input on this subject is greatly appreciated. Best Regards,Paul J Smith Teradyne, Inc., Boston, MA 02111 paul.j.sm...@teradyne.com Voice 617-422-2997 Fax 603-843-7526 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: high temperature circuitbreaker
Kristiaan In my experience when CBs operate above or close to 40degC, they will potentially operate below the rating trip point, leading to spurious trips. Especially on start up with in rush current. A CB manufacturer should be able to provide you with the devices performance curves, fault current vs time, along with a performance band for working temperature. From an approval point of view, the concern is exceeding the temp rating of the insulation and plastic body. Personally I have never had a problem with the agencies rejecting a CB fitted into a product and sitting in ambient of 50degC. After all a CB a product that does not start because a warm CB keeps tripping, remains fairly safe. Best bet though is to speak to the CB manufacturers. They will know exactly what there products are capable of, and potentially be able to offer you a high temperature version. A search on the UL web site under the CCN codes of QVNU2 or DIVQ, will produce a big list of approved CB manufacturers. kristiaan.carpent...@alcatel.be wrote: Hello group, Circuit breakers and residual current operated circuitbreakers for house-hold applications are typically cetified at 40 degree Celcius. If these types are built into other products, they do not comply with their temperature rating as specified in the safety certificate. Does any-one know about references to circuit-breakers(230V ac, 10A) that can work safely at higher temperatures (70...90 degrees) Regards, Kris Carpentier --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server. -- Andrew Carson - Product Safety Engineer, Xyratex, UK Phone: +44 (0)23 9249 6855 Fax: +44 (0)23 9249 6014 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: Motor Drive Grounding Scheme
In typical testing of DC units, the two inputs are floating when doing for example: current checks and hipot to chassis ground. Yet, in a CO, the return lead is grounded, so you have a test lab condition ( return floating ) and a real condition, return tied to CO earth ground in service. The only thing unusual might be the delta in the ground connections, causing an impedance change, thus a voltage swing. In this case its 74vdc, so its hazardous, I would think doing appropriate fault testing @ UL would be sufficient. Just saying its unsafe and NO is not reasonable. Richard, -Original Message- From: Peter Merguerian [mailto:pmerguer...@itl.co.il] Sent: Friday, October 19, 2001 3:45 AM To: 'Mark Haynes'; IEEE EMC-PSTC Discussion List (E-mail) Cc: Peter Deneault (E-mail); Tom Brenner; Doug Harris Subject: RE: Motor Drive Grounding Scheme Mark, If you think your product is safe, you must be able to prove it. For starters, I suggest you read UL60950. Somewhere in the Appendix, it allows one side of the input supply to telecommunication equipment intended for central office applications to be earthed. However, special markings andf instructions are required. Regret I do not have the time to commit for a full reasearch at this time. But, once you read the UL60950 standard, I am sure you will have a better case to explain to UL. Also, I recommend that you talk to an expert at UL rather than a low level engineer - you may try calling Jimmy Wong at UL Melville. This e-mail message may contain privileged or confidential information. If you are not the intended recipient, you may not disclose, use, disseminate, distribute, copy or rely upon this message or attachment in any way. If you received this e-mail message in error, please return by forwarding the message and its attachments to the sender. PETER S. MERGUERIAN Technical Director I.T.L. (Product Testing) Ltd. 26 Hacharoshet St., POB 211 Or Yehuda 60251, Israel Tel: + 972-(0)3-5339022 Fax: + 972-(0)3-5339019 Mobile: + 972-(0)54-838175 -Original Message- From: Mark Haynes [mailto:mhay...@dlsemc.com] Sent: Thursday, October 18, 2001 6:44 PM To: IEEE EMC-PSTC Discussion List (E-mail) Cc: Peter Deneault (E-mail); Tom Brenner; Doug Harris Subject: Motor Drive Grounding Scheme Greetings All, I work for a product safety consulting firm/test lab/agent. I am currently having some difficulties with UL relating to one of our customer's products. The grounding scheme of the products has become a barrier which has halted the planned testing. In our opinion, the engineering rationale behind this position is not very strong or clear. The products are small open-type stepper and servo motor drives (rated up to 6 A) which are intended to be used within another enclosure. They are powered by an 18 - 74 V dc external source which is supplied by the user. The drive output is a DC pulse width modulated waveform. UL 508C and UL 840 are the standards being used. The main issue is the fact that the DC - (common) input supply lead is connected internally to the input ground (PE) lead. UL has referenced UL 508C requirements (not really applicable to these particular products since we have agreed to use UL 840 for spacings) that indicate that spacings are required within the product between these two leads. This implies that this grounding scheme cannot be used. The manufacturer has indicated that the drives will not operate properly without this grounding connection. The product designers made this connection internally to prevent the common from floating above/below ground potential and for EMI purposes. The customer and my company do not agree with UL's position. One possible hazard UL stated was that the heatsink was connected to the grounded DC - (common) internal bus and could be electrically live. Since the heatsink is referenced to ground potential, it is not live during normal operation. If an internal fault does occur, the circuitry is designed such that the fault current will flow through the ground, as intended. In addition, a hint of possibly increasing the risk of shock was also mentioned. No one involved has been able to identify any real safety issues resulting from this grounding scheme. In order to address all potential safety hazards, we have recommended that testing be conducted to confirm compliance with the intent of the standards. This would hopefully show that the products are safe and that all foreseeable safety hazards (during normal and fault conditions) have been identified and minimized/eliminated. After weeks of research and discussions, we have not been able to convince UL that this grounding scheme should be allowed and that we should proceed with the testing. Does anyone know of any similar UL certified motor drives (or other similar DC powered products) that employ this grounding scheme? The closest examples we could find were AC powered products with DC ground referenced secondary
Re: What is minimum dBA measured difference above ambient noise for pulsing alarm.
Hi Paul, Sound pressure level (SPL) is normally given for sustained or peak levels for different environments. The dB(A) unit for SPL is relative to the threshold of hearing. The A in the dB(A) indicates the measurement is taken with an A-weighted filter which shapes the frequency response in a prescribed manner. Sound pressure level above ambient would be quite a different concept. For instance, room conversation is roughly 60dB(A). To get 80dB above that ambient, you'll end up with 140 dB(A)!This would be extremely loud and unsafe in my estimate. - Dan Kwok, P.Eng. Principal Engineer Electromagnetic Compatibility Intetron Consulting, Inc. Ph (604) 432-9874 E-mail dk...@intetron.com Internet http://www.intetron.com - Original Message - From: paul_j_sm...@notes.teradyne.com To: SEHS Grapevine s...@semi.org; emc-p...@majordomo.ieee.org Sent: Friday, October 19, 2001 6:56 AM Subject: Re: What is minimum dBA measured difference above ambient noise for pulsing alarm. Folks, Can anyone cite a reference document / standard that determines if there is a minimum dBA sound level variation above an expected ambient environment that is suitable for a pulsing alarm. In my review , I have found that SEMI S2-0200E Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment states in Para. 27.1 ...Equipment should be designed to control exposures to sound pressure levels equal to or greater than sound pressure levels equal to or greater than 80 dBA continuous or intermittent sound pressure level, and 120 dB instantaneous (impulse) sound pressure level. Further, 29 CFR 1910.95 Occupational noise exposure states ... 2.) If the variations in noise level involve maxima at intervals of 1 second or less, it is to be considered continuous. Are there any industry standards that recommends a pulse level variation? Your input on this subject is greatly appreciated. Best Regards,Paul J Smith Teradyne, Inc., Boston, MA 02111 paul.j.sm...@teradyne.com Voice 617-422-2997 Fax 603-843-7526 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
Light Emission from Professional Photography Flashes
Dear All, Any limitations/requirements for amount of light emitted from professional photography flashes? Any UL, IEC or European standards which specify limitations? I know how many you like being photographed - but imagine what harm one of these flashes can cause to your eyes! This e-mail message may contain privileged or confidential information. If you are not the intended recipient, you may not disclose, use, disseminate, distribute, copy or rely upon this message or attachment in any way. If you received this e-mail message in error, please return by forwarding the message and its attachments to the sender. PETER S. MERGUERIAN Technical Director I.T.L. (Product Testing) Ltd. 26 Hacharoshet St., POB 211 Or Yehuda 60251, Israel Tel: + 972-(0)3-5339022 Fax: + 972-(0)3-5339019 Mobile: + 972-(0)54-838175 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: Is This Right?
Your eqn (2) is in error. This is how it works. 10 log (aV2^2/V2^2) = 10 log (a) + 10 log (V2/V2)^2 = 10 log (a) + 20 log (V2/V2) = 10 log (a) -- From: umbdenst...@sensormatic.com To: emc-p...@majordomo.ieee.org Subject: RE: Is This Right? Date: Fri, Oct 19, 2001, 8:37 AM More to the proof discussion launched by the duty cycle question, given dB = 10 log (P1/P2) Let a be the duty cycle ratio, with 0a1, so that P1 = aP2. Then dB = 10 log (aP2/P2) = 10 log (a). Eq. (1) If 10 log (P1/P2) = 10 log (V1^2/V2^2) = 10 log (V1/V2)^2 = 20 log (V1/V2), Then does it follow that, dB = 10 log (aV2^2/V2^2) = 10 log (aV2/V2)^2 = 20 log (a) ? Eq. (2) If this is true, then duty cycle a = 10 log (a) from Eq. (1) and = 20 log (a) from Eq. (2) What am I missing? Don -- From: UMBDENSTOCK, DON Sent: Thursday, October 18, 2001 5:03 PM To: UMBDENSTOCK, DON; emc-p...@majordomo.ieee.org; stu...@timcoengr.com; 'Ken Javor' Subject: RE: duty cycle correction factors Perhaps I oversimplified. The definitions may be conditioned by what the FCC is looking for. And in general, I have always tested my understandings for a sanity check, not as a proof. So, going back to the origins of the question, in some sections the FCC refers to an averaging detector, and a preference to use duty cycle with peak detection to provide the averaging detector reading. The FCC commented that they preferred math over averaging detectors due to linearity issues (per comments on a submission). So let's test the understanding: Given a 100uV signal measured by the peak detector in my spectrum analyzer. Given a 15 % duty cycle. The FCC would call this a signal equivalent to an averaging detector output of 15uV, 100 x .15 = 15 uV. If I wanted to simplify the handling of factors, I would apply the formula 10 log (P1/P2) or 10 log (V1^2/V2^2) = 10 log (V1/V2)^2 = 2*10 log (V1/V2) or in general, 20 log (V). The signal converted to dB would be 20 log (15) or 23.5dB If I want to simplify the handling of factors, I would apply the formula to the given value, 20 log (100) or 40 dB. If I apply the test to Ken's formula 10 log (a) = 10 log (.15) we have -8.2dB. As we are multiplying in linear terms, that means we are adding in log terms. 40 + (-8.2) = 31.8 dB If we apply the formula 20 log (.15) we have -16.5 dB. 40 + (-16.5) = 23.5 dB, which compares to 23.5 dB above. There is a piece missing somewhere as demonstrated when a test is applied. Don Umbdenstock -- From: Ken Javor[SMTP:ken.ja...@emccompliance.com] Sent: Thursday, October 18, 2001 3:37 PM To: umbdenst...@sensormatic.com; emc-p...@majordomo.ieee.org; stu...@timcoengr.com Subject: Re: duty cycle correction factors I wasn't going to weigh in on this but... what was presented by Mr. Umbdenstock is equivalent to saying that since 2 + 2 = 4, then 2 x 2 = 4. It is tautological. The decibel scale is a power ratio. If a signal has a particular duty cycle then it is the total power that is affected by the duty cycle ratio. If something is on 100% and then you reduce the on-time to 50%, clearly you consume half the previous POWER. dB = 10 log (P1/P2) Let a be the duty cycle ratio, with 0a1, so that P1 = aP2. Then dB = 10 log (aP2/P2) = 10 log (a). QED. -- From: umbdenst...@sensormatic.com To: emc-p...@majordomo.ieee.org, stu...@timcoengr.com Subject: RE: duty cycle correction factors Date: Thu, Oct 18, 2001, 12:26 PM Stuart, Duty cycle in 15.231 is related to a voltage ratio, therefore 20 log(duty cycle) will provide the correct factor. Demonstrate it to yourself. Start with a given value (say 100V), multiply this by some duty cycle (say 15% or .15). Convert the result to dB. This is your reference result. Now take 20 log of a duty cycle (.15). Convert your given value (100V) to dB. Add the numbers together, duty cycle dBs to the given value dBs, and behold -- the same answer as the reference result. Best regards, Don -- From: Stuart Lopata[SMTP:stu...@timcoengr.com] Reply To: Stuart Lopata Sent: Thursday, October 18, 2001 12:00 PM To: emc Subject: duty cycle correction factors Part 15.231 devices use a duty cycle correction factor to adjust peak readings. The duty cycle represents the fractional on-time over a given period of time (that must be under some limit). Anyways, given this fractional time, d, how do you make the conversion to dB? 10log(d) or 20log(d)? There have been some misinterpretations, since the readings are made at a span of zero hertz (voltage readings). Normally, a reduction in voltage would use the 20log scale. However, since the duty cycle does not represent a scale down (it represents the off-time versus on-time), the 10log scale seems more appropriate.
RE: Is This Right?
You are missing the fact you have your brackets wrong in: dB = 10 log (aV2^2/V2^2) = 10 log (aV2/V2)^2 = 20 log (a) ? Eq. (2) should be dB = 10 log (a (V2^2/V2^2)) = 10 log a ((V2/V2)^2) = 10 log (a)Eq. (2) -Original Message- From: umbdenst...@sensormatic.com [mailto:umbdenst...@sensormatic.com] Sent: 19 October 2001 14:38 To: emc-p...@majordomo.ieee.org Subject: RE: Is This Right? More to the proof discussion launched by the duty cycle question, given dB = 10 log (P1/P2) Let a be the duty cycle ratio, with 0a1, so that P1 = aP2. Then dB = 10 log (aP2/P2) = 10 log (a). Eq. (1) If 10 log (P1/P2) = 10 log (V1^2/V2^2) = 10 log (V1/V2)^2 = 20 log (V1/V2), Then does it follow that, dB = 10 log (aV2^2/V2^2) = 10 log (aV2/V2)^2 = 20 log (a) ? Eq. (2) If this is true, then duty cycle a = 10 log (a) from Eq. (1) and = 20 log (a) from Eq. (2) What am I missing? Don -- From: UMBDENSTOCK, DON Sent: Thursday, October 18, 2001 5:03 PM To: UMBDENSTOCK, DON; emc-p...@majordomo.ieee.org; stu...@timcoengr.com; 'Ken Javor' Subject: RE: duty cycle correction factors Perhaps I oversimplified. The definitions may be conditioned by what the FCC is looking for. And in general, I have always tested my understandings for a sanity check, not as a proof. So, going back to the origins of the question, in some sections the FCC refers to an averaging detector, and a preference to use duty cycle with peak detection to provide the averaging detector reading. The FCC commented that they preferred math over averaging detectors due to linearity issues (per comments on a submission). So let's test the understanding: Given a 100uV signal measured by the peak detector in my spectrum analyzer. Given a 15 % duty cycle. The FCC would call this a signal equivalent to an averaging detector output of 15uV, 100 x .15 = 15 uV. If I wanted to simplify the handling of factors, I would apply the formula 10 log (P1/P2) or 10 log (V1^2/V2^2) = 10 log (V1/V2)^2 = 2*10 log (V1/V2) or in general, 20 log (V). The signal converted to dB would be 20 log (15) or 23.5dB If I want to simplify the handling of factors, I would apply the formula to the given value, 20 log (100) or 40 dB. If I apply the test to Ken's formula 10 log (a) = 10 log (.15) we have -8.2dB. As we are multiplying in linear terms, that means we are adding in log terms. 40 + (-8.2) = 31.8 dB If we apply the formula 20 log (.15) we have -16.5 dB. 40 + (-16.5) = 23.5 dB, which compares to 23.5 dB above. There is a piece missing somewhere as demonstrated when a test is applied. Don Umbdenstock -- From: Ken Javor[SMTP:ken.ja...@emccompliance.com] Sent: Thursday, October 18, 2001 3:37 PM To: umbdenst...@sensormatic.com; emc-p...@majordomo.ieee.org; stu...@timcoengr.com Subject:Re: duty cycle correction factors I wasn't going to weigh in on this but... what was presented by Mr. Umbdenstock is equivalent to saying that since 2 + 2 = 4, then 2 x 2 = 4. It is tautological. The decibel scale is a power ratio. If a signal has a particular duty cycle then it is the total power that is affected by the duty cycle ratio. If something is on 100% and then you reduce the on-time to 50%, clearly you consume half the previous POWER. dB = 10 log (P1/P2) Let a be the duty cycle ratio, with 0a1, so that P1 = aP2. Then dB = 10 log (aP2/P2) = 10 log (a). QED. -- From: umbdenst...@sensormatic.com To: emc-p...@majordomo.ieee.org, stu...@timcoengr.com Subject: RE: duty cycle correction factors Date: Thu, Oct 18, 2001, 12:26 PM Stuart, Duty cycle in 15.231 is related to a voltage ratio, therefore 20 log(duty cycle) will provide the correct factor. Demonstrate it to yourself. Start with a given value (say 100V), multiply this by some duty cycle (say 15% or .15). Convert the result to dB. This is your reference result. Now take 20 log of a duty cycle (.15). Convert your given value (100V) to dB. Add the numbers together, duty cycle dBs to the given value dBs, and behold -- the same answer as the reference result. Best regards, Don -- From: Stuart Lopata[SMTP:stu...@timcoengr.com] Reply To: Stuart Lopata Sent: Thursday, October 18, 2001 12:00 PM To: emc Subject: duty cycle correction factors Part 15.231 devices use a duty cycle correction factor to adjust peak readings. The duty cycle represents the fractional on-time over a given period of time (that must be under
60601-1-2
I heard that the IEC has issued the new 60601-1-2 EMC standard for medical equipment on the 30th of September. Does anyone know when the EN will follow and when its DOW will be? Thanks, Bob Heller 3M Product Safety, 76-1-01 St. Paul, MN 55107-1208 Tel: 651- 778-6336 Fax: 651-778-6252 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
high temperature circuitbreaker
Hello group, Circuit breakers and residual current operated circuitbreakers for house-hold applications are typically cetified at 40 degree Celcius. If these types are built into other products, they do not comply with their temperature rating as specified in the safety certificate. Does any-one know about references to circuit-breakers(230V ac, 10A) that can work safely at higher temperatures (70...90 degrees) Regards, Kris Carpentier --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: What is minimum dBA measured difference above ambient noise for pulsing alarm.
Folks, Can anyone cite a reference document / standard that determines if there is a minimum dBA sound level variation above an expected ambient environment that is suitable for a pulsing alarm. In my review , I have found that SEMI S2-0200E Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment states in Para. 27.1 ...Equipment should be designed to control exposures to sound pressure levels equal to or greater than sound pressure levels equal to or greater than 80 dBA continuous or intermittent sound pressure level, and 120 dB instantaneous (impulse) sound pressure level. Further, 29 CFR 1910.95 Occupational noise exposure states 2.) If the variations in noise level involve maxima at intervals of 1 second or less, it is to be considered continuous. Are there any industry standards that recommends a pulse level variation? Your input on this subject is greatly appreciated. Best Regards,Paul J Smith Teradyne, Inc., Boston, MA 02111 paul.j.sm...@teradyne.com Voice 617-422-2997 Fax 603-843-7526 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: Is This Right?
More to the proof discussion launched by the duty cycle question, given dB = 10 log (P1/P2) Let a be the duty cycle ratio, with 0a1, so that P1 = aP2. Then dB = 10 log (aP2/P2) = 10 log (a). Eq. (1) If 10 log (P1/P2) = 10 log (V1^2/V2^2) = 10 log (V1/V2)^2 = 20 log (V1/V2), Then does it follow that, dB = 10 log (aV2^2/V2^2) = 10 log (aV2/V2)^2 = 20 log (a) ? Eq. (2) If this is true, then duty cycle a = 10 log (a) from Eq. (1) and = 20 log (a) from Eq. (2) What am I missing? Don -- From: UMBDENSTOCK, DON Sent: Thursday, October 18, 2001 5:03 PM To: UMBDENSTOCK, DON; emc-p...@majordomo.ieee.org; stu...@timcoengr.com; 'Ken Javor' Subject: RE: duty cycle correction factors Perhaps I oversimplified. The definitions may be conditioned by what the FCC is looking for. And in general, I have always tested my understandings for a sanity check, not as a proof. So, going back to the origins of the question, in some sections the FCC refers to an averaging detector, and a preference to use duty cycle with peak detection to provide the averaging detector reading. The FCC commented that they preferred math over averaging detectors due to linearity issues (per comments on a submission). So let's test the understanding: Given a 100uV signal measured by the peak detector in my spectrum analyzer. Given a 15 % duty cycle. The FCC would call this a signal equivalent to an averaging detector output of 15uV, 100 x .15 = 15 uV. If I wanted to simplify the handling of factors, I would apply the formula 10 log (P1/P2) or 10 log (V1^2/V2^2) = 10 log (V1/V2)^2 = 2*10 log (V1/V2) or in general, 20 log (V). The signal converted to dB would be 20 log (15) or 23.5dB If I want to simplify the handling of factors, I would apply the formula to the given value, 20 log (100) or 40 dB. If I apply the test to Ken's formula 10 log (a) = 10 log (.15) we have -8.2dB. As we are multiplying in linear terms, that means we are adding in log terms. 40 + (-8.2) = 31.8 dB If we apply the formula 20 log (.15) we have -16.5 dB. 40 + (-16.5) = 23.5 dB, which compares to 23.5 dB above. There is a piece missing somewhere as demonstrated when a test is applied. Don Umbdenstock -- From: Ken Javor[SMTP:ken.ja...@emccompliance.com] Sent: Thursday, October 18, 2001 3:37 PM To: umbdenst...@sensormatic.com; emc-p...@majordomo.ieee.org; stu...@timcoengr.com Subject:Re: duty cycle correction factors I wasn't going to weigh in on this but... what was presented by Mr. Umbdenstock is equivalent to saying that since 2 + 2 = 4, then 2 x 2 = 4. It is tautological. The decibel scale is a power ratio. If a signal has a particular duty cycle then it is the total power that is affected by the duty cycle ratio. If something is on 100% and then you reduce the on-time to 50%, clearly you consume half the previous POWER. dB = 10 log (P1/P2) Let a be the duty cycle ratio, with 0a1, so that P1 = aP2. Then dB = 10 log (aP2/P2) = 10 log (a). QED. -- From: umbdenst...@sensormatic.com To: emc-p...@majordomo.ieee.org, stu...@timcoengr.com Subject: RE: duty cycle correction factors Date: Thu, Oct 18, 2001, 12:26 PM Stuart, Duty cycle in 15.231 is related to a voltage ratio, therefore 20 log(duty cycle) will provide the correct factor. Demonstrate it to yourself. Start with a given value (say 100V), multiply this by some duty cycle (say 15% or .15). Convert the result to dB. This is your reference result. Now take 20 log of a duty cycle (.15). Convert your given value (100V) to dB. Add the numbers together, duty cycle dBs to the given value dBs, and behold -- the same answer as the reference result. Best regards, Don -- From: Stuart Lopata[SMTP:stu...@timcoengr.com] Reply To: Stuart Lopata Sent: Thursday, October 18, 2001 12:00 PM To: emc Subject: duty cycle correction factors Part 15.231 devices use a duty cycle correction factor to adjust peak readings. The duty cycle represents the fractional on-time over a given period of time (that must be under some limit). Anyways, given this fractional time, d, how do you make the conversion to dB? 10log(d) or 20log(d)? There have been some misinterpretations, since the readings are made at a span of zero hertz (voltage readings). Normally, a reduction in voltage would use the 20log scale. However, since the duty cycle does not represent
Passive Laser Devices
Hi Guys, I've been in a lot of trouble this week and had a lot of questions. But, my way of thinking is...if you're not in a little trouble, you're not in the game. Anyway...we want to purchase fiber optic switches for use with our OTDR (Optical Time Domain Reflectometer) modules. The switches and OTDR modules mount in a Compact PCI chassis as separate cards. We have always labeled our OTDR modules with their respective laser classification, submitted to the CDRH... Our current modules are all Class I according to CDRH and EN 60825-1. There may be some future modules with Class III power levels. From this point, assume that the modules are labeled and compliant with CDRH and EN 60825-1. Now, what about the fiber optic switch cards that route the OTDR output? My thinking is this... the cards should be labelled with a generic laser radiation warning label without a specific classification. This warning label would refer the user to the manual where verbage such as...Treat the all output ports of the switch with caution appropriate to the class of the source fed to the input (paraphrased) Others have said that we should label the switches at the time of sale with the laser classification of their accompanying module. I have two problems with this... 1. The switch is not a laser device. It has no classification of its own. 2. There is no guarantee in the field that the switch will always be used to route radiation within the power levels of its marked classification. For example, what if a user buys an OTDR and switch combination both labeled Class I. Then, later, they upgrade their OTDR to a Class III module. In this case I believe that the Class I label on the switch would be misleading and give a false sense of security. Knowledgable users know that Class I is eye safe. I also don't want to rely on us trying to track units and send new labels to the user for their switch if they upgrade their OTDR. There is no guarantee that they would get installed. There is no guarantee that we could track units that well. I would rather have the switch give no classification at all and force the user to find out what power levels are routed through it.(by reading the laser class tags on the source feeding it). My other line of thinking is that all switches could be marked with the worst case classification (Class III). But I still don't like that because we don't have control at the user level. The worst case module that WE would sell them with a switch is Class III. But who knows what other signals the user could route through? They could always route a higher power through the switch and render our labeling misleading and inappropriate. Again, I fall back to the generic label and forcing the user to know what power levels they are dealing with. As always, the advice and experience of my colleagues (comiserators) is welcomed and appreciated. Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: Motor Drive Grounding Scheme
Mark, If you think your product is safe, you must be able to prove it. For starters, I suggest you read UL60950. Somewhere in the Appendix, it allows one side of the input supply to telecommunication equipment intended for central office applications to be earthed. However, special markings andf instructions are required. Regret I do not have the time to commit for a full reasearch at this time. But, once you read the UL60950 standard, I am sure you will have a better case to explain to UL. Also, I recommend that you talk to an expert at UL rather than a low level engineer - you may try calling Jimmy Wong at UL Melville. This e-mail message may contain privileged or confidential information. If you are not the intended recipient, you may not disclose, use, disseminate, distribute, copy or rely upon this message or attachment in any way. If you received this e-mail message in error, please return by forwarding the message and its attachments to the sender. PETER S. MERGUERIAN Technical Director I.T.L. (Product Testing) Ltd. 26 Hacharoshet St., POB 211 Or Yehuda 60251, Israel Tel: + 972-(0)3-5339022 Fax: + 972-(0)3-5339019 Mobile: + 972-(0)54-838175 -Original Message- From: Mark Haynes [mailto:mhay...@dlsemc.com] Sent: Thursday, October 18, 2001 6:44 PM To: IEEE EMC-PSTC Discussion List (E-mail) Cc: Peter Deneault (E-mail); Tom Brenner; Doug Harris Subject: Motor Drive Grounding Scheme Greetings All, I work for a product safety consulting firm/test lab/agent. I am currently having some difficulties with UL relating to one of our customer's products. The grounding scheme of the products has become a barrier which has halted the planned testing. In our opinion, the engineering rationale behind this position is not very strong or clear. The products are small open-type stepper and servo motor drives (rated up to 6 A) which are intended to be used within another enclosure. They are powered by an 18 - 74 V dc external source which is supplied by the user. The drive output is a DC pulse width modulated waveform. UL 508C and UL 840 are the standards being used. The main issue is the fact that the DC - (common) input supply lead is connected internally to the input ground (PE) lead. UL has referenced UL 508C requirements (not really applicable to these particular products since we have agreed to use UL 840 for spacings) that indicate that spacings are required within the product between these two leads. This implies that this grounding scheme cannot be used. The manufacturer has indicated that the drives will not operate properly without this grounding connection. The product designers made this connection internally to prevent the common from floating above/below ground potential and for EMI purposes. The customer and my company do not agree with UL's position. One possible hazard UL stated was that the heatsink was connected to the grounded DC - (common) internal bus and could be electrically live. Since the heatsink is referenced to ground potential, it is not live during normal operation. If an internal fault does occur, the circuitry is designed such that the fault current will flow through the ground, as intended. In addition, a hint of possibly increasing the risk of shock was also mentioned. No one involved has been able to identify any real safety issues resulting from this grounding scheme. In order to address all potential safety hazards, we have recommended that testing be conducted to confirm compliance with the intent of the standards. This would hopefully show that the products are safe and that all foreseeable safety hazards (during normal and fault conditions) have been identified and minimized/eliminated. After weeks of research and discussions, we have not been able to convince UL that this grounding scheme should be allowed and that we should proceed with the testing. Does anyone know of any similar UL certified motor drives (or other similar DC powered products) that employ this grounding scheme? The closest examples we could find were AC powered products with DC ground referenced secondary circuits. However, this is not the same since a transformer usually provides the required isolation. Does anyone have any comments/information on this grounding scheme that might be helpful in building a stronger case either way? The closest thing we could reference was a grounded DC distribution system in the 1999 National Electrical Code (NEC - NFPA 70). Please respond at your earliest convenience. Thanks in advance for your assistance, Mark A. Haynes Senior Product Safety Engineer D.L.S. Conformity Assessment, Inc. 1250 Peterson Drive Wheeling, IL 60090-6454 (847) 537-6400 (Ext. 157) Fax (847) 537-6488 mhay...@dlsemc.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your
RE: Motor Drive Grounding Scheme
Mark. As described, the situation to me sounds no worse than any other earthed connection. The only hazard would seem to be as a return for hazardous voltages - exactly the same situation as the sheet metal enclosure that surrounds it. In my experience sometimes the approver's representative makes a snap judgement when confronted with something unfamiliar. It then becomes difficult for them to back down without losing face. I would suggest gently trying to convince the representative of the logic of your position. Scott Lacey -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Mark Haynes Sent: Thursday, October 18, 2001 12:44 PM To: IEEE EMC-PSTC Discussion List (E-mail) Cc: Peter Deneault (E-mail); Tom Brenner; Doug Harris Subject: Motor Drive Grounding Scheme Greetings All, I work for a product safety consulting firm/test lab/agent. I am currently having some difficulties with UL relating to one of our customer's products. The grounding scheme of the products has become a barrier which has halted the planned testing. In our opinion, the engineering rationale behind this position is not very strong or clear. The products are small open-type stepper and servo motor drives (rated up to 6 A) which are intended to be used within another enclosure. They are powered by an 18 - 74 V dc external source which is supplied by the user. The drive output is a DC pulse width modulated waveform. UL 508C and UL 840 are the standards being used. The main issue is the fact that the DC - (common) input supply lead is connected internally to the input ground (PE) lead. UL has referenced UL 508C requirements (not really applicable to these particular products since we have agreed to use UL 840 for spacings) that indicate that spacings are required within the product between these two leads. This implies that this grounding scheme cannot be used. The manufacturer has indicated that the drives will not operate properly without this grounding connection. The product designers made this connection internally to prevent the common from floating above/below ground potential and for EMI purposes. The customer and my company do not agree with UL's position. One possible hazard UL stated was that the heatsink was connected to the grounded DC - (common) internal bus and could be electrically live. Since the heatsink is referenced to ground potential, it is not live during normal operation. If an internal fault does occur, the circuitry is designed such that the fault current will flow through the ground, as intended. In addition, a hint of possibly increasing the risk of shock was also mentioned. No one involved has been able to identify any real safety issues resulting from this grounding scheme. In order to address all potential safety hazards, we have recommended that testing be conducted to confirm compliance with the intent of the standards. This would hopefully show that the products are safe and that all foreseeable safety hazards (during normal and fault conditions) have been identified and minimized/eliminated. After weeks of research and discussions, we have not been able to convince UL that this grounding scheme should be allowed and that we should proceed with the testing. Does anyone know of any similar UL certified motor drives (or other similar DC powered products) that employ this grounding scheme? The closest examples we could find were AC powered products with DC ground referenced secondary circuits. However, this is not the same since a transformer usually provides the required isolation. Does anyone have any comments/information on this grounding scheme that might be helpful in building a stronger case either way? The closest thing we could reference was a grounded DC distribution system in the 1999 National Electrical Code (NEC - NFPA 70). Please respond at your earliest convenience. Thanks in advance for your assistance, Mark A. Haynes Senior Product Safety Engineer D.L.S. Conformity Assessment, Inc. 1250 Peterson Drive Wheeling, IL 60090-6454 (847) 537-6400 (Ext. 157) Fax (847) 537-6488 mhay...@dlsemc.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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: No longer online until our new server is brought online and the old messages are imported into the new server.
