How to Check Continuity in a Long Wire

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Often when troubleshooting there comes a time to check the continuity of a wire. If both ends of the wire are close together this is a simple task.

Just set your meter to continuity and put a lead on either end of the wire. Done.

When the wire is already installed and the ends are far apart this can be a more difficult task. Luckily after reading this guide you’ll be able to check wires with ease.

How to check the wire.

This is easiest with someone to help but can be done by one person. If you’re by yourself this test will just require a bit of extra walking.

To verify the integrity of the wire involves grounding and un-grounding while metering continuity.

  • Make sure the power going to the wire is off.
  • Disconnect both ends of the wire to be tested. The wire ends shouldn’t be touching anything.
  • Set your meter to continuity and put one lead to ground and one to the end of the wire you are working on. Your tester will display OL as there shouldn’t be a path to ground unless the wire is damaged.
  • Ground out one end of the wire. Usually, I’m working in a PLC cabinet when doing this test. Most of the time there is a spare ground terminal on the DIN rail that I can terminate the wire in.
  • Go to the end of the wire that isn’t grounded and check for continuity to ground. Now that the other end of the wire is grounded you should read a continuity to ground. If you’ve got someone helping you it’s a good idea to have them ground and un-ground the wire a few times just to ensure the readings are correct.

Grounding one end of the wire and metering continuity proves the integrity of the conductor. If there was a break in the wire you wouldn’t be able to read continuity to ground from the opposite end.

It’s never fun tracking down electrical problems but now you’ll be able to test for broken wires with ease.

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