Hi Ken and the group, The model started out in IEC 801-2 which had a 150 Ohm, 150 pF model. This eventually became IEC 6000-4-2 at 330 Ohms and 150 pF. Both were meant to model a piece of metal in a human hand. Such a discharge is an order of magnitude more severe, even for a tiny piece of metal in one's hand, than a discharge directly from a human hand if one measures the radiated EMI from these events. The R and C above were the result of many measurements on people. The first engineers to describe the IEC 61000-4-2 pulse as it is today, with the sharp peak at the start, was Michael King and David Reynolds back when dinosaurs roamed the earth in the last century. There is a semiconductor device handling spec called "Human Body Model" using 100 pF and 1500 Ohms. But, for me, there are no good HBM simulators on the market as they all have metallic tips. They need a tip composed of material that has the same volume and surface resistivity as a human finger. There it goes, now no one can patent the idea...it is now in the public domain. Since capacitance goes by surface area, we may need a new capacitance value as the population has gained weight. I propose we replace BMI (Body Mass Index) with the BCI (Body Capacitance Index) a combination of body free space capacitance in pF of a person and the number of nanoseconds (at one foot per nanosecond) it takes for light to go from head to foot. Like BCI = [body capacitance]/[body length in nanoseconds at the speed of light]. For me that might be about 25 pF/ns. Some of my friends might be about 45 pF/ns. Wow, two ideas in the same email! Doug On Tue, 19 Jun 2018 15:34:57 -0500, Ken Javor wrote: What with Doug Smith being active in this sort of standard writing activity, I doubt it’s simply inertia. Ken Javor Phone: (256) 650-5261 From: John Woodgate <[email protected]> Date: Tue, 19 Jun 2018 21:26:38 +0100 To: Ken Javor <[email protected]>, <[email protected]> Subject: Re: [PSES] ESD question Probably handed down on a stone tablet in 1910 and no-one had the courage to challenge it yet. (;-) John Woodgate OOO-Own Opinions Only J M Woodgate and Associates www.woodjohn.uk <http://www.woodjohn.uk> Rayleigh, Essex UK On 2018-06-19 21:18, Ken Javor wrote: ESD question Anyone out there know the origins of the 150 pF/330 ohm gun model used in EN61000-4-2 and derivative standards? It seems it ought to be a human body model, but it isn't. Ken Javor Phone: (256) 650-5261 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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