ESD Systems - Questions And Answers

We have an ESD conductive floor in our electrical assembly area and were using ESD foot/heel -straps. We have demanded that all operators in the area wear steel toed safety shoes. The operators in the area have obtained ESD safety shoes and they do not pass our foot strap tester unless they are wearing the foot/heel straps. The foot straps we use are the Plastic Systems #24080. The shoes from XXXX XXX reduce static electricity by maintaining a level of electrical resistance of 1E6 to 1E8 Ohms. Should I get a new tester or new shoes or what? - Anthony, Windsorlocks, CT

First, make sure your tester has been recently calibrated, if not have your tester calibrated. The standard for testing shoes is different than heel grounders. The standard ESD S9.1-1995 uses a 100 Volt resistance meter for obtaining resistance readings below 1E9 Ohms. Most heel strap testers apply an open circuit voltage between 6 to 12 volts, well below 100 volts for shoes. If the sole material of the shoes takes a larger voltage to show conductive properties, than either get a higher voltage tester or reevaluate what is important in the control of static discharges when wearing high resistant shoes at low voltages. Some foot ground [heel strap] testers are factory set between a range of 750 kilohms to 100 Megohms and others have a high range of only 10 Megohms. There are some new testers that apply about 20 to 22 volts open circuit and might help too. further, there are some ESD shoes that will test on foot-ground testers because they conduct more freely (in the dissipative range) at lower voltages.

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