Re: [PSES] classification of the output
Hi Mick: In 1961, James J. Gibson published a paper entitled “The contribution of experimental psychology to the formulation of the problem of safety: a brief for basic research.” This paper reported his studies of injury causation in automobile accidents: “Injuries to a living organism can be produced only by some energy interchange. Consequently, a most effective way of classifying sources of injury is according to the forms of physical energy involved. The analysis can thus be exhaustive and conceptually clear. Physical energy is either mechanical, thermal, radiant, chemical, or electrical.” In other words, Joules transferred to (or from) a body cause injury. Actually, Joules per second. In an automobile accident, a lot of kinetic energy can be transferred to a body in a short time. Wikipedia gives some practical examples of one Joule of energy: https://en.wikipedia.org/wiki/Joule Gibson’s thesis is the basis for IEC 62368. So, we have ES, electrical energy source, MS, mechanical (kinetic) energy source, PS, power source (fire), RS, radiation energy source, and TS, thermal energy source. For ES, a watt-second is a Joule. E x I is a watt. The standard limits both E and I individually (but we always have both and therefore have watts transferred to the body). Time is forever. For higher voltages and currents, we limit the time, such as a GFCI (but not in IEC 62368). All of the other energy sources can be similarly shown to be based on Joules per second. For the most part, the standard assumes the energy available for transfer to the body is steady state. Note that the body can safely absorb energy when Joules/second is small. The body has several thresholds for energy which depend on the energy format. In IEC 62368, three thresholds for each energy format are given: detectable, painful, and injurious, hence ES1, ES2, and ES3, etc. The requirements are based on the body response to a parameter, which is why there is no reference to TNV or similar parameter. Hope this helps. Best regards, Rich From: Mick Maytum Sent: Thursday, March 14, 2019 10:09 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] classification of the output Pete, Glad to see your thoughts agree with mine. With large amplitude voltage pulses there must be some EMC considerations that come into play for equipment EMC compliance. I really wish that some alternative abbreviation had been created instead of ES. Many engineers would be looking for a Joule parameter for an energy source, yet Joules don't get a direct mention in the IEC 62368-1 body text description (Why no entry in definitions?). Expressing ES as a voltage, current and charged capacitance (no inductive current) makes it multi-option classification. Further when it comes to telecommunications TNV circuits, those are classified by DC working voltage alone. Thus they are ES1 or ES2 DC working voltage circuits not simply ES1 or ES2 circuits as that would drag all the other ES factors in. - 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] classification of the output - SawStop
Hi, Ed. I expect it senses current, whether that's through a resistance or a capacitance. Best wishes John Woodgate OOO-Own Opinions Only J M Woodgate and Associates www.woodjohn.uk Rayleigh, Essex UK On 2019-03-15 04:19, Edward Price wrote: *Pete:* ** *Does the SawStop operate by sensing leakage current through the human finger to ground, or does it sense the human body’s capacitance (like those touch sensors that control small table lamps)?* ** *Also, I read their literature, but I didn’t see any mention of false-positive actions. Is there some white-paper that SawStop has which might have some better technical details?* ** */Ed Price /**WB6WSN**/ /**Chula Vista, CA USA* ** *From:*Pete Perkins [mailto:0061f3f32d0c-dmarc-requ...@listserv.ieee.org] *Sent:* Thursday, March 14, 2019 5:26 PM *To:* EMC-PSTC@LISTSERV.IEEE.ORG *Subject:* Re: [PSES] classification of the output Joe, I am familiar with this product that stops the saw blade and protects fingers. I talked with them during development; their primary problem was that the product wasn’t explicitly covered under the standards for the product they were intending this for. We discussed paths to changing the standard (which takes years, too long) or convincing major customers that the product was acceptable even without the 3^rd party approval. It all seemed too long range so they proceeded on their own and were eventually successful. I’ve seen the demo video but don’t have it or know where it might reside; the demo was amazing and convincing. Has there been a search on You-tube yet? Maybe Rich Nute knows where such might be hidden. :>) br, Pete Peter E Perkins, PE Principal Product Safety & Regulatory Affairs Consultant PO Box 23427 Tigard, ORe 97281-3427 503/452-1201 IEEE Life Fellow p.perk...@ieee.org <mailto:p.perk...@ieee.org> Entropy ain’t what it used to be - 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 mailto:emc-p...@ieee.org>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas mailto:sdoug...@ieee.org>> Mike Cantwell mailto:mcantw...@ieee.org>> For policy questions, send mail to: Jim Bacher mailto:j.bac...@ieee.org>> David Heald mailto:dhe...@gmail.com>> - 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] classification of the output - SawStop
Pete: Does the SawStop operate by sensing leakage current through the human finger to ground, or does it sense the human body’s capacitance (like those touch sensors that control small table lamps)? Also, I read their literature, but I didn’t see any mention of false-positive actions. Is there some white-paper that SawStop has which might have some better technical details? Ed Price WB6WSN Chula Vista, CA USA From: Pete Perkins [mailto:0061f3f32d0c-dmarc-requ...@listserv.ieee.org] Sent: Thursday, March 14, 2019 5:26 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] classification of the output Joe, I am familiar with this product that stops the saw blade and protects fingers. I talked with them during development; their primary problem was that the product wasn’t explicitly covered under the standards for the product they were intending this for. We discussed paths to changing the standard (which takes years, too long) or convincing major customers that the product was acceptable even without the 3rd party approval. It all seemed too long range so they proceeded on their own and were eventually successful. I’ve seen the demo video but don’t have it or know where it might reside; the demo was amazing and convincing. Has there been a search on You-tube yet? Maybe Rich Nute knows where such might be hidden. :>) br, Pete Peter E Perkins, PE Principal Product Safety & Regulatory Affairs Consultant PO Box 23427 Tigard, ORe 97281-3427 503/452-1201 IEEE Life Fellow p.perk...@ieee.org<mailto:p.perk...@ieee.org> Entropy ain’t what it used to be - 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] classification of the output
Pete, Glad to see your thoughts agree with mine. With large amplitude voltage pulses there must be some EMC considerations that come into play for equipment EMC compliance. I really wish that some alternative abbreviation had been created instead of ES. Many engineers would be looking for a Joule parameter for an energy source, yet Joules don't get a direct mention in the IEC 62368-1 body text description (Why no entry in definitions?). Expressing ES as a voltage, current and charged capacitance (no inductive current) makes it multi-option classification. Further when it comes to telecommunications TNV circuits, those are classified by DC working voltage alone. Thus they are ES1 or ES2 DC working voltage circuits not simply ES1 or ES2 circuits as that would drag all the other ES factors in. Regards, Mick Safety and Telecom Standards mjmay...@gmail.com https://ict-surge-protection-essays.co.uk/ -- Original Message -- From: "Pete Perkins" To: "Mick Maytum" ; EMC-PSTC@listserv.ieee.org Sent: 13/03/2019 06:11:38 Subject: RE: [PSES] classification of the output Mick, Thanx for the reply given on this thread. I am familiar with the 60479 clauses you describe. My overall comment is that 60479 folks primary focus is on preventing VF (not killing people). Much of what you quoted relates to such electric shock situations. Because of the data spread there probably are a few folks who lie below the curves shown in the standard. Tasers meet these requirements yet there are occasional deaths with their use; the ‘almost perfect weapon’ in my opinion. In the product standards the allowed electric shock level is always set much lower so that the VF region is not involved. The upper limit to electric shock from equipment is the Letgo-immobilization limit of 5mArms/7mApk under fault conditions. The long time separation to allow the heart to reset doesn’t come into play for this effect so it is irrelevant. The peak current is the major factor that needs to be controlled. :>) br, Pete Peter E Perkins, PE Principal Product Safety & Regulatory Affairs Consultant PO Box 23427 Tigard, ORe 97281-3427 503/452-1201 IEEE Life Fellow p.perk...@ieee.org Entropy ain’t what it used to be From: Mick Maytum Sent: Tuesday, March 12, 2019 1:03 PM To:EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] classification of the output Joe Randolph and I talked about “pulsed power” delivery at the 2019 ATIS-PEG conference last week and how it should be treated. A good starting point is the IEC 60479 series of documents on “Effects of current on human beings and livestock”. IEC 62368-1 mentions the time locked IEC TS 60479-1:2005, but the current version is IEC 60479-1:2018. The IEC TS 60479-2:2017 variant is particularly interesting as clause 9 covers “Effects of current pulse bursts and random complex irregular waveforms”. For sequential pulses separated by > 300 ms there isn’t a cumulative effect on the heart and each pulse can be treated as single, non-repetitive pulse of current. For safety, I believe pulsed power systems will insert this separation time when any non-load currents are detected to delay any following power pulse. Thus only the effects of a single power pulse need to be evaluated provided the safety separation is >0.3 s. Primarily IEC TS 60479-2:2017 is seeking to establish a “no fibrillation” condition, which is higher stress level than you’d want for a safety standard. A 2018 ATIS-PEG conference paper on IEC TS 60479-2:2017 gave an example evaluation using the quoted pulsed currents produced by a TASER® gun. Safety tip - if anyone is pointing a TASER® gun at you, yell out you have a pre-existing medical condition. Image removed by sender. Regards, Mick Safety and Telecom Standards mjmay...@gmail.com https://ict-surge-protection-essays.co.uk/ -- Original Message -- From: "Joe Randolph" To: EMC-PSTC@listserv.ieee.org Sent: 12/03/2019 17:54:36 Subject: Re: [PSES] classification of the output Hi Pete: This discussion reminds me of some things I have been hearing about “digital power” as a way to deliver large amounts of power while keeping the circuit classification to ES1 or ES2. A company called Voltserver has been promoting (and deploying) this technology. I know few details about the scheme, and I’m not familiar with how IEC 62368-1 evaluates things such as touch current. However, as I understand it, the “digital power” method uses a series of short pulses with off periods during which the power sourcing device attempts to detect a fault condition. The power is immediately cut off if a fault condition is detected. I have heard that the pulse frequency is in the range of 7 KHz, and the voltages can be up to 380 V. The key to making this scheme even plausible is that the s
Re: [PSES] classification of the output
Joe, I think that you are referring to the SawStop invented by Steve Glass. https://www.youtube.com/watch?v=dekzPA6nhC4 shows it in action. John Barnes KS4GL, PE, NCE, NCT, ESDC Eng, ESDC Tech, PSE, Master EMC Design Eng, SM IEEE (retired) 216 Hillsboro Ave Lexington, KY 40511-2105 (859)253-1178 phone jrbar...@iglou.com http://www.dbicorporation.com/ - 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] classification of the output
Is it not possible to refer such a divergence to TC108 for a ruling on interpretation? Maybe even an Interpretation Sheet would be generated if the 'ES2' test house has misunderstood the standard. Best wishes John Woodgate OOO-Own Opinions Only J M Woodgate and Associates www.woodjohn.uk Rayleigh, Essex UK On 2019-03-13 21:21, Richard Nute wrote: Hi Boštjan: If you say ES1 and another certification body says ES2, then a negotiation must take place. To avoid negotiation, you must change your verdict to ES2. However, the manufacturer wants ES1, which is determined by the voltage. I agree that the voltage waveform is ES1 value, and the current is not. But only one parameter, voltage or current, is needed to determine ES1. Good luck, and best regards, Rich *From:*Glavič *Sent:* Tuesday, March 12, 2019 10:34 PM *To:* EMC-PSTC@LISTSERV.IEEE.ORG *Subject:* Re: [PSES] classification of the output Hi Pete, What manufacturer is expecting is the exact answer. Does this output complies with ES1 or it is ES2? And of course justification for this decision. If I accept it as ES1 and then later the other certification body says it is ES2 it is a big problem for the manufacturer. If you see below my understanding how can we interpret the standard then separation to AC and DC part for the single pulse is not required and limit is always 60Vpk. Do you agree? There is no limitation for maximum duration of the single pulse in the standard. Also pulse off time is not clear (is it time when pulse voltage is at zero or the time when pulse voltage is below certain voltage). I know that as a member of HBSDT and OSM I have tools in my hands however I do not see a quick solution. So some experiences and opinions from members of this group are appreciated. The question that was previously raised at TC was a bit different, it was not a pulsing waveform. Best regards, Bostjan - 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 mailto:emc-p...@ieee.org>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas mailto:sdoug...@ieee.org>> Mike Cantwell mailto:mcantw...@ieee.org>> For policy questions, send mail to: Jim Bacher mailto:j.bac...@ieee.org>> David Heald mailto:dhe...@gmail.com>> - 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] classification of the output
Hi Boštjan: If you say ES1 and another certification body says ES2, then a negotiation must take place. To avoid negotiation, you must change your verdict to ES2. However, the manufacturer wants ES1, which is determined by the voltage. I agree that the voltage waveform is ES1 value, and the current is not. But only one parameter, voltage or current, is needed to determine ES1. Good luck, and best regards, Rich From: Glavič Sent: Tuesday, March 12, 2019 10:34 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] classification of the output Hi Pete, What manufacturer is expecting is the exact answer. Does this output complies with ES1 or it is ES2? And of course justification for this decision. If I accept it as ES1 and then later the other certification body says it is ES2 it is a big problem for the manufacturer. If you see below my understanding how can we interpret the standard then separation to AC and DC part for the single pulse is not required and limit is always 60Vpk. Do you agree? There is no limitation for maximum duration of the single pulse in the standard. Also pulse off time is not clear (is it time when pulse voltage is at zero or the time when pulse voltage is below certain voltage). I know that as a member of HBSDT and OSM I have tools in my hands however I do not see a quick solution. So some experiences and opinions from members of this group are appreciated. The question that was previously raised at TC was a bit different, it was not a pulsing waveform. Best regards, Bostjan - 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] classification of the output
Mick, Thanx for the reply given on this thread. I am familiar with the 60479 clauses you describe. My overall comment is that 60479 folks primary focus is on preventing VF (not killing people). Much of what you quoted relates to such electric shock situations. Because of the data spread there probably are a few folks who lie below the curves shown in the standard. Tasers meet these requirements yet there are occasional deaths with their use; the ‘almost perfect weapon’ in my opinion. In the product standards the allowed electric shock level is always set much lower so that the VF region is not involved. The upper limit to electric shock from equipment is the Letgo-immobilization limit of 5mArms/7mApk under fault conditions. The long time separation to allow the heart to reset doesn’t come into play for this effect so it is irrelevant. The peak current is the major factor that needs to be controlled. :>) br, Pete Peter E Perkins, PE Principal Product Safety & Regulatory Affairs Consultant PO Box 23427 Tigard, ORe 97281-3427 503/452-1201 IEEE Life Fellow <mailto:p.perk...@ieee.org> p.perk...@ieee.org Entropy ain’t what it used to be From: Mick Maytum Sent: Tuesday, March 12, 2019 1:03 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] classification of the output Joe Randolph and I talked about “pulsed power” delivery at the 2019 ATIS-PEG conference last week and how it should be treated. A good starting point is the IEC 60479 series of documents on “Effects of current on human beings and livestock”. IEC 62368-1 mentions the time locked IEC TS 60479-1:2005, but the current version is IEC 60479-1:2018. The IEC TS 60479-2:2017 variant is particularly interesting as clause 9 covers “Effects of current pulse bursts and random complex irregular waveforms”. For sequential pulses separated by > 300 ms there isn’t a cumulative effect on the heart and each pulse can be treated as single, non-repetitive pulse of current. For safety, I believe pulsed power systems will insert this separation time when any non-load currents are detected to delay any following power pulse. Thus only the effects of a single power pulse need to be evaluated provided the safety separation is >0.3 s. Primarily IEC TS 60479-2:2017 is seeking to establish a “no fibrillation” condition, which is higher stress level than you’d want for a safety standard. A 2018 ATIS-PEG conference paper on IEC TS 60479-2:2017 gave an example evaluation using the quoted pulsed currents produced by a TASER® gun. Safety tip - if anyone is pointing a TASER® gun at you, yell out you have a pre-existing medical condition. Regards, Mick Safety and Telecom Standards <mailto:mjmay...@gmail.com> mjmay...@gmail.com https://ict-surge-protection-essays.co.uk/ -- Original Message -- From: "Joe Randolph" mailto:j...@randolph-telecom.com> > To: EMC-PSTC@listserv.ieee.org <mailto:EMC-PSTC@listserv.ieee.org> Sent: 12/03/2019 17:54:36 Subject: Re: [PSES] classification of the output Hi Pete: This discussion reminds me of some things I have been hearing about “digital power” as a way to deliver large amounts of power while keeping the circuit classification to ES1 or ES2. A company called Voltserver has been promoting (and deploying) this technology. I know few details about the scheme, and I’m not familiar with how IEC 62368-1 evaluates things such as touch current. However, as I understand it, the “digital power” method uses a series of short pulses with off periods during which the power sourcing device attempts to detect a fault condition. The power is immediately cut off if a fault condition is detected. I have heard that the pulse frequency is in the range of 7 KHz, and the voltages can be up to 380 V. The key to making this scheme even plausible is that the system must respond VERY quickly to a fault condition (such as a human touching a live conductor). I’m interested in hearing your thoughts (and hopefully Rich Nute’s thoughts too) regarding how the touch current tests in IEC 62368-1 might apply to such a system. I don’t know whether such a system would pass or fail the IEC 62368-1 tests. Regardless of whether such a system would pass or fail the existing tests in IEC-62368-1, I think the important thing is to go back to first principles and evaluate whether the proposed “digital power” can be made sufficiently safe to prevent harm to humans. Thanks, Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) <mailto:j...@randolph-telecom.com> j...@randolph-telecom.com <http://www.randolph-telecom.com> http://www.randolph-telecom.com - This message is from the IEEE Product Safety Engin
Re: [PSES] classification of the output
Joe Randolph and I talked about “pulsed power” delivery at the 2019 ATIS-PEG conference last week and how it should be treated. A good starting point is the IEC 60479 series of documents on “Effects of current on human beings and livestock”. IEC 62368-1 mentions the time locked IEC TS 60479-1:2005, but the current version is IEC 60479-1:2018. The IEC TS 60479-2:2017 variant is particularly interesting as clause 9 covers “Effects of current pulse bursts and random complex irregular waveforms”. For sequential pulses separated by > 300 ms there isn’t a cumulative effect on the heart and each pulse can be treated as single, non-repetitive pulse of current. For safety, I believe pulsed power systems will insert this separation time when any non-load currents are detected to delay any following power pulse. Thus only the effects of a single power pulse need to be evaluated provided the safety separation is >0.3 s. Primarily IEC TS 60479-2:2017 is seeking to establish a “no fibrillation” condition, which is higher stress level than you’d want for a safety standard. A 2018 ATIS-PEG conference paper on IEC TS 60479-2:2017 gave an example evaluation using the quoted pulsed currents produced by a TASER® gun. Safety tip - if anyone is pointing a TASER® gun at you, yell out you have a pre-existing medical condition. Regards, Mick Safety and Telecom Standards mjmay...@gmail.com https://ict-surge-protection-essays.co.uk/ -- Original Message -- From: "Joe Randolph" To: EMC-PSTC@listserv.ieee.org Sent: 12/03/2019 17:54:36 Subject: Re: [PSES] classification of the output Hi Pete: This discussion reminds me of some things I have been hearing about “digital power” as a way to deliver large amounts of power while keeping the circuit classification to ES1 or ES2. A company called Voltserver has been promoting (and deploying) this technology. I know few details about the scheme, and I’m not familiar with how IEC 62368-1 evaluates things such as touch current. However, as I understand it, the “digital power” method uses a series of short pulses with off periods during which the power sourcing device attempts to detect a fault condition. The power is immediately cut off if a fault condition is detected. I have heard that the pulse frequency is in the range of 7 KHz, and the voltages can be up to 380 V. The key to making this scheme even plausible is that the system must respond VERY quickly to a fault condition (such as a human touching a live conductor). I’m interested in hearing your thoughts (and hopefully Rich Nute’s thoughts too) regarding how the touch current tests in IEC 62368-1 might apply to such a system. I don’t know whether such a system would pass or fail the IEC 62368-1 tests. Regardless of whether such a system would pass or fail the existing tests in IEC-62368-1, I think the important thing is to go back to first principles and evaluate whether the proposed “digital power” can be made sufficiently safe to prevent harm to humans. Thanks, Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com http://www.randolph-telecom.com - 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] classification of the output
Ted has proposed something that safety standards committees do not do: EXPERIMENTS to prove or disprove the requirements. But I have done voltage, current, and thermal experiments on students (voluntarily) at the Energy Class 1 levels in my HBSE courses. One of the more interesting experiments was that of 60 Hz constant current source, where one current limiter (0.5 mA short-circuit) was a resistance and another was a capacitance. Most volunteers could not or could barely feel the current from the resistive source. However, most volunteers felt an unpleasant jolt from the capacitive source. This was probably the discharge from the charged capacitor. But to John’s point. When I was in grade school (1st grade, I think), my father had replaced the spark coil in our ’35 Plymouth. So, I got to play with the old one. It would still work sometimes. I used one of the old, cylindrical 1.5-volt dry cells, probably 2 inches in diameter and 8 inches tall. I would give myself shocks from the thing. I took it to school, and had all the kids (and teacher) hold hands in a big circle. The first time I touched the wires to generate the pulse – nothing. The nervous kids relaxed. The second time it worked, and all enjoyed (experienced) the current pulse! Anyway, I would guess that Boštjan’s 50-volt, 700-millisecond pulse would be easily felt – even to the extent that many would say that it was unacceptable. Experiment? But it complies with the ES1 requirements in the standard! Best regards, Rich From: Ted Eckert <07cf6ebeab9d-dmarc-requ...@listserv.ieee.org> Sent: Tuesday, March 12, 2019 8:21 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] classification of the output Although the recent discussion has been in humor, it does make me think of a more practical experiment along these lines. I wonder how many HBSDT and TC108 members have an intuitive understanding of what the limits are? I wish I had time to set this up and bring it to the next USTAG meeting, but I don’t have the time or the resources. However, I would propose a “Class 1 energy experience center”. There would be a number of stations were people could experience the limits of class 1 energy sources. You could experience both AC and DC voltages at the ES1 limits. There would be a chance to touch currents at the AC and DC limits of ES1. I would want a number of plastic, glass and metal surfaces at the various TS1 limits in Table 38 of IEC 62368-1. There could be a set of light sources of various frequencies at the IEC 62471 Risk Group 1 limits. I don’t think I’ve ever tried to place my hand on a 71 C glass surface for 10 seconds to see what it feels like. On the other hand, I have had some unintentional experience with contact with ES2 and ES3 voltage sources. Long ago, I was holding onto the PCB of a modem plugged into a live phone line. I got to experience the voltage of a ring signal when somebody called. It didn’t make me jump, but I involuntarily flung that modem as far as the phone line would let it fly. Ted Eckert Microsoft Corporation The opinions expressed are my own and do not necessarily reflect those of my employer. From: John Allen <09cc677f395b-dmarc-requ...@listserv.ieee.org <mailto:09cc677f395b-dmarc-requ...@listserv.ieee.org> > Sent: Tuesday, March 12, 2019 7:34 AM To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] classification of the output “Question to the House”: to what extent should one take into account “how high they jump” as that may depend on their normal reaction times, their susceptibility to “shocks”, their body mass – and how much they ate and drank for lunch? :) John E Allen W. London, UK. From: Pete Perkins [ <mailto:0061f3f32d0c-dmarc-requ...@listserv.ieee.org> mailto:0061f3f32d0c-dmarc-requ...@listserv.ieee.org] Sent: 12 March 2019 14:14 To: <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] classification of the output John, I like your approach – run a test to determine the resolution of this issue :>) :>) br, Pete Peter E Perkins, PE Principal Product Safety & Regulatory Affairs Consultant PO Box 23427 Tigard, ORe 97281-3427 503/452-1201 IEEE Life Fellow p.perk...@ieee.org <mailto:p.perk...@ieee.org> Entropy ain’t what it used to be From: John Woodgate mailto:j...@woodjohn.uk> > Sent: Tuesday, March 12, 2019 1:15 AM To: Pete Perkins mailto:peperkin...@cs.com> >; EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] classification of the output Simple question - long and very significant answer. I recommend arranging the HBSDT members in a circle and applying the voltage between two adjacent members. If more than
Re: [PSES] classification of the output
Hi Boštjan: Following up on my previous comment. Chances are the IEC 60990 touch current measurement scheme will not have a steady state current, but instead a fluctuating current. Especially if the PS output has a source impedance during the "off" state, which would discharge the touch current measurement circuit. An oscilloscope would give you a good measurement, especially if you used a digital scope that could be set up to measure the average current (voltage) over a full cycle. Best regards, Rich - 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] classification of the output
True AF-1 story, circa 1987. Baggage loader, acquired for AF-1 in case they had to be someplace that didn't have one. Basically a stowable conveyer belt. Motors were 400 cycle synchronous ac - no EMI. But the deploy/stow process used multiple relays and solenoids (transient noise). When I saw this as part of the AF-1 suite of equipment, my assessment was no possibility of EMI other than short transients; used only on the ground, no need to EMI qualify. Someone overruled me, and it was qualified at a commercial test facility using a Fairchild Electro-Metrics FSS-250. While that won't mean much to most readers, the salient point is that it was an EMI receiver tied to a pen-plotter (chart recorder) real time. Which means there was a lot of inertia in the recording process, so that transients had to be handled differently than cw signals. For transients, the scanning had to stop, the pen was at one position and the cycling or whatever caused the transient was exercised with pen at the one position (frequency). Then the pen was moved to another frequency and the process repeated. Shampoo, rinse, repeat. The test frequencies were actually enshrined in MIL-STD-462, back in the day. And there relaxations of the limit for these transients. 20 dB for mode-switching, 50 dB for on-off, if memory serves. The reason for all this was the pen was so massive that the peak detector had to hold the signal level a long time, relative to scanning sped. So if you used that long time on a transient but were scanning, the pen would stay up at the peak of the transient over quite a distance (frequency range) before it would suddenly drop back to normal. If you understood how the machine worked and you saw a trace where this has happened, it was immediately obvious what was going on. But the test facility didn't understand any of this, and let the machine simply scan through the deployment and stow operations. I was on a trip and got a call from the engineer who had overruled me on the baggage loader EMI qualification decision. He told me that the baggage loader had failed EMI. It had failed, he said, "miserably." I can still hear him saying that, savoring the words as he spoke them. I told him it was impossible. But instead of coming home, I had to go to the facility, and troubleshoot the problem. When I arrived and saw the data, it was immediately obvious they had used the receiver incorrectly, and I showed them the wording in the MIL-STD, and they repeated the test and all was well - no fixes were necessary. So even on AF-1, short duration infrequent transients are permissible... Ken Javor Phone: (256) 650-5261 > From: John Woodgate > Date: Fri, 8 Mar 2019 16:04:52 + > To: Ken Javor , > Subject: Re: [PSES] classification of the output > > Trouble is, you can never be sure . It might be Air Force 1 that gets > the EMI! > > On 2019-03-08 15:56, Ken Javor wrote: >> Re: [PSES] classification of the output Unless the output overload >> test modeled something that occurred fairly often in practice, it >> seems to me that EMI caused during such an event would not be a >> serious issue. >> >> Ken Javor >> Phone: (256) 650-5261 >> >> >> >> *From: *John Woodgate >> *Reply-To: *John Woodgate >> *Date: *Fri, 8 Mar 2019 09:41:41 + >> *To: * >> *Subject: *Re: [PSES] classification of the output >> >> >> >> There are serious EMC implications as well. Since most EMC testing >> doesn't cover overload conditions, the effect you describe could >> result in many complaints of EMI in the field. >> >> >> Best wishes >> John Woodgate OOO-Own Opinions Only >> J M Woodgate and Associates www.woodjohn.uk <http://www.woodjohn.uk> >> <http://www.woodjohn.uk> >> Rayleigh, Essex UK >> >> On 2019-03-08 09:24, Boštjan Glavič wrote: >> >> >> >> >> >> Dear all, >> >> >> >> I would need your advice about classification of the output of >> power supply during abnormal operation. I know that quite many >> discussions were already done, but this was with regard of touch >> current. >> >> >> >> During output overload test unit goes in hiccup mode. There are >> more than 3s between main pulses. Pulse voltage does not exceed >> 60V (see picture 1). The problem is that each pulse (hiccup) is >> composed of small pulses (see second picture). How to treat this >> output? >> >> >> >> Customer is not happy with ES2 classif
Re: [PSES] classification of the output
Hi Bostjan, This is an interesting question. A few thoughts: - Have you measured the touch current? Per 5.2.2.5 for repetitive pulses, if the voltage exceeds the limit of Table 8, then the current shall not exceed the limit. So if your peak touch current is less than 0.707 mA, ES1 classification is OK independently of which voltage limit you apply. - This is supported by the description of ES2 in 5.2.1.2, which requires an ES2 circuit to exceed *both* the ES1 prospective touch voltage limit and the ES1 touch current limit. - 0.707mA appears to be the most stringent touch current limit from Table 4, so if you don't exceed this value it doesn't really matter if you classify it as a repetitive peak voltage or combined ac/dc. - If you don't like the touch current route, you could probably make an argument for treating the longer pulse as combined ac/dc. It does have a frequency and does not meet the definition of d.c. voltage in 3.3.14.1, but single pulses with off time >3s use the dc limits for ES1 based on Tables 6 and 7. So you could consider the single pulse portion as not actually dc, but that the dc limits are appropriate to apply. The touch current route is cleaner as it is clearly supported in the standard. On Fri, Mar 8, 2019 at 8:05 AM John Woodgate wrote: > Trouble is, you can never be sure . It might be Air Force 1 that gets > the EMI! > > On 2019-03-08 15:56, Ken Javor wrote: > > Re: [PSES] classification of the output Unless the output overload > > test modeled something that occurred fairly often in practice, it > > seems to me that EMI caused during such an event would not be a > > serious issue. > > > > Ken Javor > > Phone: (256) 650-5261 > > > > > > > > *From: *John Woodgate > > *Reply-To: *John Woodgate > > *Date: *Fri, 8 Mar 2019 09:41:41 + > > *To: * > > *Subject: *Re: [PSES] classification of the output > > > > > > > > There are serious EMC implications as well. Since most EMC testing > > doesn't cover overload conditions, the effect you describe could > > result in many complaints of EMI in the field. > > > > > > Best wishes > > John Woodgate OOO-Own Opinions Only > > J M Woodgate and Associates www.woodjohn.uk <http://www.woodjohn.uk> > > <http://www.woodjohn.uk> > > Rayleigh, Essex UK > > > > On 2019-03-08 09:24, Boštjan Glavič wrote: > > > > > > > > > > > > Dear all, > > > > > > > > I would need your advice about classification of the output of > > power supply during abnormal operation. I know that quite many > > discussions were already done, but this was with regard of touch > > current. > > > > > > > > During output overload test unit goes in hiccup mode. There are > > more than 3s between main pulses. Pulse voltage does not exceed > > 60V (see picture 1). The problem is that each pulse (hiccup) is > > composed of small pulses (see second picture). How to treat this > > output? > > > > > > > > Customer is not happy with ES2 classification. > > > > > > > > Can we each pulse separate to AC and DC part and try with limit > > for Combined AC and DC? > > > > > > > > Thank you for your support. > > > > > > > > Best regards, > > > > Bostjan > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Picture 1 – output hiccup. > > > > > > > > > > > > Picture 2 – zoom of individual pulse > > > > > > > > > > > > - > > > > > > 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 > > > > > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieee-pses.org/emc-pstc.html > > > > > > Attachments are not permitted but the IEEE PSES Online Communities > > site at http://product-compliance.oc.ieee.org/ can be used for > > graphics (in well-used formats), large files, etc. > > > > > > Website: http://www.ieee-pses.org/ > > Instructions: http://www.ieee-pses.org/list.html (including how > > to unsubscribe) <http://www.ieee-pses.org/l
Re: [PSES] classification of the output
Trouble is, you can never be sure . It might be Air Force 1 that gets the EMI! On 2019-03-08 15:56, Ken Javor wrote: Re: [PSES] classification of the output Unless the output overload test modeled something that occurred fairly often in practice, it seems to me that EMI caused during such an event would not be a serious issue. Ken Javor Phone: (256) 650-5261 *From: *John Woodgate *Reply-To: *John Woodgate *Date: *Fri, 8 Mar 2019 09:41:41 + *To: * *Subject: *Re: [PSES] classification of the output There are serious EMC implications as well. Since most EMC testing doesn't cover overload conditions, the effect you describe could result in many complaints of EMI in the field. Best wishes John Woodgate OOO-Own Opinions Only J M Woodgate and Associates www.woodjohn.uk <http://www.woodjohn.uk> <http://www.woodjohn.uk> Rayleigh, Essex UK On 2019-03-08 09:24, Boštjan Glavič wrote: Dear all, I would need your advice about classification of the output of power supply during abnormal operation. I know that quite many discussions were already done, but this was with regard of touch current. During output overload test unit goes in hiccup mode. There are more than 3s between main pulses. Pulse voltage does not exceed 60V (see picture 1). The problem is that each pulse (hiccup) is composed of small pulses (see second picture). How to treat this output? Customer is not happy with ES2 classification. Can we each pulse separate to AC and DC part and try with limit for Combined AC and DC? Thank you for your support. Best regards, Bostjan Picture 1 – output hiccup. Picture 2 – zoom of individual pulse - 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald - 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 All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher David Heald - 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 mailto:emc-p...@ieee.org>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas mailto:sdoug...@ieee.org>> Mike Cantwell mailto:mcantw...@ieee.org>> For policy questions, send mail to: Jim Bacher mailto:j.bac...@ieee.org>> David Heald mailto:dhe...@gmail.com>> --- This email has been checked for viruses by AVG. https://www.avg.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send
