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 Posted: Mon Sep 08, 2026 11:43 am Post subject: What's the 1-megaohm R in wrist straps for? |
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| What's the 1 M-ohm resistance of the wrist strap for? Isn’t it better to have zero resistance to ground?
Udong M |
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Joined: 20 Jun 2026
Posts: 17
| Posted: Mon Sep 08, 2026 1:18 pm Post subject: |
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| I read that this is for personal safety of the operator. Any explanation, guys?
Test Engg 99 |
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Joined: 16 Jun 2026
Posts: 108
Location: Paranaque City, Phils.
| Posted: Mon Sep 08, 2026 1:31 pm Post subject: |
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| The 1 mega-ohm resistance incorporated into a wrist strap is indeed for the protection of employees from electrical shock. In the remote possibility that the common ground inadvertently gets electrically connected to a ‘live’ line (that’s 230VAC if the ‘live’ line is our AC supply), the 1 M-ohm resistor will limit the current flow through the person to V/1e6, or 230 microamps if V=230VAC. Such a small current will not be perceptible to many of us.
For example, many companies now use the neutral or ground wire (third wire) of the AC supply as common ground, since this makes it very easy to ground all equipment on the line. Thus, any inadvertent occurrence of a short between one supply line with this ground wire can ‘shock’ any operator connected to this common ground if she doesn't have 1 meg between her and the ground. EE |
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