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Although @120V and IEC/UL acceptable leakage of 500uA, the wrist strap could be reduced to 240k with the same safe limit, but not for EOS parts. So you could say for both reasons, but the primary protection is the parts, otherwise why not 10M? That would be safer for humans, but that is not the main purpose of an "EOS protected workplace", but workplace safety is also important.

***Although Vac line voltage both IEC/UL acceptable leakage is 500uA for line filters etc, so one could reason that the wrist strap could be reduced to 240k with the same safe limit, but not for EOS sensitive parts. So you could say for both reasons, but the primary reason for protection is the EOS sensitive parts, otherwise why not 10M? or 22M or 50M? *** That would be safer for humans, but that is not the main purpose of an "EOS protected workplace", but workplace safety is also important.

The reason for the acceptable range of 1M to 10 M is to current limit static discharge for wrist straps.

The reason for the acceptable range of 1M to 10 M is to current limit static discharge for wrist straps. in addition it reduces current to live voltages.

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Although @120V and IEC/UL acceptable leakage of 500uA, the wrist strap could be reduced to 240k with the same safe limit, but not for EOS parts. So you could say for both reasons, but the primary protection is the parts, otherwise why not 10M? That would be safer for humans, but that is not the main purpose of an "EOS protected workplace", but workplace safety is also important.

The reason for the acceptable range of 1M to 10 M is to current limit static discharge.

The reason for the acceptable range of 1M to 10 M is to current limit static discharge for wrist straps.

• It does this by bleeding body charge slowly to the same potential of the case or gnd reference that the 1M resistor is clamped to, while static charge may be generated by motion or change in body capacitance with a fixed charge, V=C/Q .

• Thus for example, consider a 10000 pf body surface to stray air charged at 10kV then connected to a 1M current limiting resistor, we might expect 10k/1M or 10mA with a decay time of 1M*10nF=10ms which is faster than pre-ionization time, so the resistor might be bypassed. But with it connected all the time, the rate of charge build up dV/dt is much slower than the discharge time so body charge levels are kept at relatively low levels.

• meanwhile the finger tip model of 100-300pF * 1M = 100u-300us decay time keeps fingers with wrist straps to ground discharged faster from tribe-electric effects and thus momentary charge build up of 1kV is limited to 1mA.

to verify this understanding yourself, recall the current zap you heard with a key or finger to metal ESD discharge and compare your experience touching a grounded tree (not paint or plastic) due to surface resistance, you likely would not feel anything and yet this can be enough to damage unprotected microwave FETs with 25V BDV, but your experience tells you the series surface resistance limited the current.