Questions And Answers

Best practice is every shift or whenever re-enetering the ESD protected area.  The ESD Association guidance is to test at least daily. See advice below.

“The wrist strap system should be tested daily to ensure proper electrical value. Nominally, the upper resistance reading should be </= 10 megohms or a user-defined value. Daily testing may be omitted if constant monitoring is used.

NOTE: Integrated Wrist Strap Checker's operation should be verified per the manufacturer's instructions.” [ANSI/ESD S1.1 Annex A, 3. Frequency of Functional Testing]

ESD Handbook ESD TR20.20 section 5.3.2.4.4 Test Frequency “Wrist straps should be tested periodically. The frequency of testing, however, is driven by the amount of risk exposure that can occur between tests. For, example, what is the quantity of product handled between test periods?”
“Because wrist straps have a finite life, it is important to develop a test frequency that will guarantee integrity of the system. Typical test programs recommend that wrist straps that are used daily should be tested daily. However, if the products that are being produced are of such value that knowledge of a continuous, reliable ground is needed, and then continuous monitoring should be considered or even required.”