ESD and Static Control Questions
Answered by the experts at Ground Zero Electrostatics
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Q: Hi, I am a fresh ESD engineer. I need to perform a testing on ESD chair by using 5 pound Megohmmeter. I encountered a problem when I was trying to test on the backrest and rear of backrest. The backrest is a vertical plate, how to put a 5 pound electrode perpendicular to that surface? Even ANSI/ESD STM 12.1 2006 also not mentioned clearly about the testing on the backrest. Can I hold the 5 pound electrode by my hands so that it is contact with surface of the backrest? Or is there any other proper way?”
A: Hello, I understand your frustration with some of these tests.
It sounds like you’ve got all the proper testing equipment and you’re following the best procedures for this. The main concern is to see that the seat, seat back and arms are making good contact to the personnel, that personnel is wearing the proper clothing so as to enable the combination of personnel to chair to esd flooring system to electrical ground are enabling the tribocharge to recombine to earth. If you have an ESD chair that includes a static conductive/dissipative seat, back, arms, casters, etc. we can make these resistance measurements to the chair’s groundable point, to a plate sitting underneath a caster, and ultimately, all the way across the floor to earth ground.
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Q: Is it necessary to use an ESD Chair when the humany body is already grounded through a Wrist Strap, Footwear or Heel Strap when working in an EPA?
A: I think it’s a great idea. I can be sitting at a workstation with an ESD flooring system, have a wrist strap on and when I get out of my chair, not generate more than 50 volts. I may not generate more than 5 volts. But what if I take my wrist strap off and jump out of my chair? I can easily generate 100’s of volts. Oh, by the way, jumping should not be allowed in an EPA. If you have great ESD shoes or sole grounders and you keep at least one foot firmly planted on the ground at all times, then maybe your ESD chair is redundant, but still an added piece to the chain in your EPA system.
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