Desco Asia - Questions And Answers

Dear Sir:
Our wrist strap and footwear limit has been set at 35M ohm. The compliance verification is done on monthly basis by using a standard resistor decade box.
Question: The footwear and wrist strap system would have a certian percentage (10%) tolerence and the decade resistor have a tolerence. When we perform verification compliance at 35M the tester still shows pass and 36M it shows fail. As per the ANSI/ESD S20.20 the compliance required limit for personnel grounding is <35M.
During audit, the auditor ask to check the wrist strap/footwear verification and found that the tester is showing pass at 35.5 M and fail at 36M limit. Although my explaination is due to the resistor tolenrence of the tester and the decade box, but the auditor did not buy the explaination and he says that the standrad required limit is <35M.
Need you input on this.

Depending upon your Tester, it can be adjusted to ensure that it does not pass personnel grounding above 3.5 x 10E7 ohms which is the upper limit per Table 2 of ANSI/ESD S20.20-2007 for Wrist Strap System and Flooring-Footwear System.

For example, see SmartLog X3 at http://www.esdsystems.com/ESDCatalog/TestingMonitoringEquipment/PeriodicWristFootTesters/DataLoggerInterface/DescoEMITDataLoggers/50430/ and Technical Bulletin TB-6502 at http://documents.esdsystems.com/PDF/TB-6502.pdf On page 3 noted tolerance of the 3.5 x 10E7 ohm setting is +/- 10%. This does allow a pass for a operator as high as 3.85 x 10E7 ohms. This has been industry practice for decades.

Related Categories:

If you have found this Q/A useful, please rate it based on its helpfulness.

This question has been rated:

(0% at 0 Ratings)

Site Map | Terms & Conditions | Privacy Policy