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 <[email protected]> Sent: Tuesday, March 12, 2019 8:21 AM To: [email protected] 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 <[email protected] <mailto:[email protected]> > Sent: Tuesday, March 12, 2019 7:34 AM To: [email protected] <mailto:[email protected]> 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:[email protected]> mailto:[email protected]] Sent: 12 March 2019 14:14 To: <mailto:[email protected]> [email protected] 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 [email protected] <mailto:[email protected]> Entropy ain’t what it used to be From: John Woodgate <[email protected] <mailto:[email protected]> > Sent: Tuesday, March 12, 2019 1:15 AM To: Pete Perkins <[email protected] <mailto:[email protected]> >; [email protected] <mailto:[email protected]> 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 50% of the members jump at 3 s intervals, it's ES2. Best wishes John Woodgate OOO-Own Opinions Only J M Woodgate and Associates www.woodjohn.uk <https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.woodjohn.uk&data=02%7C01%7Cted.eckert%40microsoft.com%7C5ba9de06559e4d5678ee08d6a6f83041%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636879982240839940&sdata=5Q%2BhlmwQ71MmM9Hg6atNZdRsan7%2F6tsH8%2F4Tg73s7h0%3D&reserved=0> Rayleigh, Essex UK On 2019-03-12 01:52, Pete Perkins wrote: - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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