Questions And Answers

Increasingly the default Wrist Strap Tester upper limit is set at 35 megohms to match the ANSI/ESD S20.20 wrist strap system less than 3.5 x 10^7 ohms (35 megohm). However, many wrist strap testers use an upper limit of 1 x 10^7 ohms (10 megohms) as that was the limit for many years in the wrist strap standard ANSI/ESD S1.1.

Per ANSI/ESD S1.1-2006 Table 3 “Functional Testing Limit for wrist strap system continuity is < or = 10 megohms or user defined value”.

Of course, 10 megohms is less than 35 megohms, so the 10 megohm setting does meet ANSI/ESD S20.20. Moreover, it is unlikely a failure would occur in the range between the two numbers, but, if so, it would be poor contact or a dry skin condition.  Most users would like to be aware of this problem at the 10 megohm level and not wait until it is at the 35 megohm level to take action.

Other possible causes for a wrist strap system to fail high would be if there is a break in the wrist strap wire, or if the current limiting resistor blows open. These failures should be detected whether the tester upper limit is set for 35 or 10 megohms.