ESD Systems - Questions And Answers

The answer to question 6 says that if the operator, ESD mat, etc. are at the same potential, there will be no opportunity for an ESD event. My question is, if the mat was hard ground and the operator had a 1 Megohm resistor in the wrist strap to ground, then there is a potential for damage, correct? - Jim, Dallas, TX

Not necessarily, but you are right that when current passes through a 1 Megohm resistor that there is a potential difference between either end of the resistor. The key in ESD control is to eliminate the charge on the body or other conductor within a safe discharge time. If the discharge time is 10 milliseconds, then there is a potential difference between the ends of a 1 Megohm resistor from 0 seconds to 0.01 seconds. Typical body movement is about 500 milliseconds (0.5 s), so by the time your hand reaches the sensitive device, you have already dissipated that potential to 0 volts with 490 milliseconds to spare.

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