Testing ESD wrist straps: limits and how often

The limit

Both ANSI/ESD S20.20 and IEC 61340-5-1 ask for the wrist strap system, person and strap together, to read below 3.5 x 10^7 ohm (35 megohm). Cords normally include a 1 megohm resistor for safety.

How often

• Many sites test every wearer at the start of each shift.
• Where the work is critical, a continuous monitor checks the connection all the time and alarms if it fails.
• Your ESD control programme plan sets the exact interval and records. Follow the plan and your standard.

How to test

1. Put the strap on as for normal work, snug against bare skin.
2. Plug the cord into the wrist strap tester.
3. Press the test button and read the pass or fail result.
4. If it fails, check the strap fit, the cord and the connections, then replace the part that failed.
5. Record the result.

Common reasons for failure

• Loose strap or dirty skin contact.
• A broken cord, often near the plug or the strap.
• A worn snap stud.
• Hand cream or lotion under the strap.

Keep reading

• ESD wrist straps and grounding
• ESD wrist straps
• ESD audit checklist