It's probably not ethnicity directly, but skin resistance. This varies
greatly between people. Long years ago, when we had touch-contact
channel change on TVs, we had to double the sensitivity so that one
particular person in the lab could work it. When we took sets to a show,
someone turned up who couldn't work it. We found it necessary to double
the sensitivity again. If you think about a person standing in the ESD
field asa large (poorly-) conducting body, you can see why the effect
can occur.
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK
On 2018-06-20 14:06, Jim Hulbert wrote:
Somewhere, I have copies of the discharge waveforms (captured on a
scope) from human subjects that Michael King recruited during his
studies. As I recall, the amplitude of the ESD pulses was limited to
about 10kV as the subjects started to balk.
I believe Michael’s studies also led to the development of the Andy
Hish 255 probe. The waveform from that probe, which was a long wand
grasped in the hand, was influenced by the human body capacitance of
the technician performing the tests. There was a situation some
years ago in our EMC Lab, where my associate and I both consistently
passed a product for ESD using the Andy Hish probe, which was our
corporate standard tester at the time. However, an intern working
with us consistently failed the product. We did our best to make sure
we were all following the exact same test technique. The only
difference my associate and I could think of was that the intern was
of a different ethnicity than us. We didn’t dare mention that, however.
*Jim Hulbert*
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