Checking if an outlet is earthed with a multimeter? - Page 1
Forum section: electronics / general

author: XOIIO
author_rank: Super Contributor
timestamp: July 03, 2014, 10:45:01 am
content: Hey all, the little "site wiring fault" is on, on the UPS that I use for my PC in the house we moved to, I remember there was a way to check if an outlet is earthed with a multimeter, but I can't recall what it was, just resistance between neutral and earth or something?Just don't want to wreck my meter doing this (It's a uni-T 71 series, and they say not to go over 30v AC. The scientist in me wants to try it, but the rest of me stops me since it was fairly expensive lol)

author: Wytnucls
author_rank: Super Contributor
timestamp: July 03, 2014, 12:15:11 pm
content: Meter selection on Vac. Probes between line and ground wires should show line voltage for a properly grounded outlet. Neutral to ground should of course read 0 volts. (That's assuming the house wiring complies with regulations)Might be safer to check that ground wires are installed, with a connection to a common earthing ground pin.

author: djococaud
author_rank: Regular Contributor
timestamp: July 04, 2014, 06:45:31 am
content: If only one Outlet is dodgy, you can just test continuity beween two outlets earth pins (use an earthed extension cord if needed)...

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: July 04, 2014, 07:21:26 am
content: You might also get the "wiring fault" light if the poles are reversed.

author: G7PSK
author_rank: Super Contributor
timestamp: July 04, 2014, 07:31:54 am
content: Get yourself a Canadian/US version of one of these, cheap and give a quick indication of faults on a socket.http://www.ebay.co.uk/itm/240v-Mains-3-pin-UK-house-wiring-plug-in-socket-correct-polarity-tester-checker-/310985803520?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item486832c700

author: Lee697
author_rank: Regular Contributor
timestamp: July 04, 2014, 08:06:25 am
content: I had a fuse box replaced once, and some wiring redone, afterwards, the sparky clipped a lead to the cold tap connection, then trailing a long test lead went and probed every earth socket in the house for continuity.

author: Kjelt
author_rank: Super Contributor
timestamp: July 04, 2014, 08:13:48 am
content: If you have a good working 35mA switch off residual-current device (RCD), or residual-current circuit breaker (RCCB) in your installation you can properly test the outlet with a (well isolated) circuit that flows for one second 40mA from the mains connector to the earth connector, for instance a relay with a power resistor capable of handling this current/voltage and power in a well isolated box.If the socket is correctly connected and properly earthed the RCD will trip, if not, nothing happens.

author: German_EE
author_rank: Super Contributor
timestamp: July 04, 2014, 01:41:07 pm
content: "afterwards, the sparky clipped a lead to the cold tap connection, then trailing a long test lead went and probed every earth socket in the house for continuity."Now THAT was a man who was worth the money!To answer the original question. If your meter only goes to 30V AC then borrow or buy one that goes to at least 600V. You should measure line voltage between Live and Neutral and also between Live and Ground. If you see more than 2V or so between Neutral and Ground then you may have a fault.PLEASE TAKE GREAT CARE WHEN MEASURING MAINS VOLTAGESHold the two meter probes in one hand and put your other hand into your pocket. Never work on mains circuits when you're alone.

author: rsjsouza
author_rank: Super Contributor
timestamp: July 04, 2014, 04:11:30 pm
content: If you use an outlet tester, just be aware of the issue reported by the article below:http://ecmweb.com/contractor/failures-outlet-testing-exposed

author: G7PSK
author_rank: Super Contributor
timestamp: July 04, 2014, 05:27:43 pm
content: A good reason for ring mains as a single mis-wired socket would blow the fuse or trip if wired hot to ground, I supose it dose not preclude some clown totally mis-wiring the whole ring.

author: XOIIO
author_rank: Super Contributor
timestamp: July 04, 2014, 06:26:39 pm
content: Quote from: rsjsouza on July 04, 2014, 04:11:30 pmSo, would that be indication of a wiring fault? lol.I thin I will grab a socket tester, though on ebay Canada they don't pop up when searching, there is an amprobe #ST102A for $16 or so when you factor in shipping.edit: found one a bit cheaper so ordered it, couple bucks cheaper.

author: Neilm
author_rank: Super Contributor
timestamp: July 04, 2014, 06:39:00 pm
content: Quote from: G7PSK on July 04, 2014, 05:27:43 pmThat happened to me at work. The place had been rewired after arsonists set fire to one of the adjacent units. We moved back in and I was assembling a prototype unit. Every thing worked then I connected the Earth. Touched the case and got a shock. The whole row of units were mis-wired. As they were owned by differnet people, insured by different companies and had been fixed by another firm the arguments on who was to blame took months to resolve.