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Question Will the constant monitor work in situations where additional series resistance to the standard 1 Mohm in the cord is needed?  We have areas where high voltage is present and now install a series 5 Mohm resistor between ground and the wrist strap connector installed on the bench.  How should the continuous monitor be connected in this situation?

Personnel grounding, including using a wrist strap and continuous monitor, should not be used if there is there may be inadvertent contact with high voltage.


Per ESD Handbook ESD TR20.20-2008 Wrist Strap section “For personnel safety, wrist straps should not be used in situations where there is an exposed electrical circuit of 250 volts or higher.”


Per ESD Handbook ESD TR 20.20 section Introduction and Purpose / General Information "The primary method of static charge control is direct connection to ground for conductors, static dissipative materials, and personnel. A complete static control program must also deal with isolated conductors that cannot be grounded, insulating materials (e.g., most common plastics), and moving personnel who cannot use wrist or heel straps or ESD control flooring and footwear.

Air ionization can neutralize the static charge on insulated and isolated objects by charging the molecules of the gases of the surrounding air."


When equipment voltage exceeds 250 volts, guidance should be obtained from the appropriate Safety Officer. The Safety Officer has to make the determination if the worker has any risk of being exposed to the high voltage. If the Safety Officer determines that the high voltage is adequately insulated and isolated, then personal grounding, which is more effective and less expensive, can be used.


Wrist Straps are Underwriter Laboratories listed. UL cautions that these products are not recommended for use on equipment with operating voltage exceeding 250 volts.


UL Marking for Wrist Strap:


“This product is not recommended for use on equipment with operating voltage exceeding 250 volts.

A one megohm resistor is molded into Wrist Strap Coil Cords. DO NOT REMOVE. If it becomes damaged, replace Coil Cord immediately. These products are not to be used in areas where the individual may come in contact with exposed electrical circuitry exceeding 250 volts.

These products are for ElectroStatic control. They will not reduce or increase your risk of receiving electrical shock when using or working on electrical equipment. Follow the same precautions you would use without wrist straps, including:

• Make certain that equipment having a grounding type plug is properly grounded.

• Make certain that you are not in contact with grounded objects other than through the Wrist Strap.”

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