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ESD, Resistor placement, and Current/Voltage basics.

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mspagon

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If you wanted ESD to flow to ground why would you put a 1M ohm resistor in its way on the path to ground, as the manual suggests? Wouldn't you want the circuit to simply be a wire with the least resistance possible?

What happens in the case that 2000V potential is generated from walking on the carpet in the winter and then an ESD static shock hits the wire, which has approximately no resistance to ground, let's say 1 ohm. Does this mean that I = V/R would lead to 2000 Amps being dissipated? Just seems unreal to me that a tiny shock could generate 2000A! Wouldn't this fry the wire? What about power? P=I^2R = (2000 A)^2 (1 ohm) =4,000,000 Watts????

Thanks all.

Workstation.jpg
 

chuckey

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You use the 10 M ohms to discharge ESD at a low current and still to give you isolation from any fault which would put mains on the connection of the equipment. You are right that thousands of amps would flow but only for a very short time, this pulse would radiate very very and induce phantom currents and voltages all over the place, hence the 10 M ohms,
Frank
 

dick_freebird

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These resistors are not for conducting ESD, they are for
preventing the workstation from becoming a charged
source while maintaining a safely low current in case of
some electrical fault. They also prevent ESD current from
being excessively large (kV/Mohm = mA max, which ought
to be survivable - although the gross capacitance may
still let you do CDM damage). But grounded workstation
and grounded workpiece equals no ESD potential and
that is the main plan - make the workstation a known
quantity, and then incoming workpiece potential is the
only issue.
 

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