Socket testers

[FredFlintstone]

Just wondering how these things work. You know, the little devices that plug into sockets and have a series of lights to indicate whether or not it's wired up properly.

How does it sense if the earth is connected or if polarity is reversed? Does it have batteries in and sends a small current through the ring or does it rely on using current from the electrical supply (and therefore requires the power to be on.

I'm not really considering using one and never have considered using one really because the testing is very limited - I'm having much more comprehensive checks carried out once I've finished my project. I was just curious how they work - is it basically a three pronged continuity tester? How does it know if the earth is earthed? I assume it doesn't.

Cheers

Fred.

 

[JohnD]

IIRC it does a rough voltage check between the pins

Between P and N should be "about" 230

Between P and E should be "about 230 but maybe not as much"

Between E and N should be "not much"

It will detect a few gross faults; but, on a ring, will not show up a common problem - one or more of the conductors broken, but each in only one place. Luckily it is very easy to do a continuity and resistance check by taking the socket off to spot this one.

 

[FredFlintstone]

Cheers John.

Fred.

 

[Adam_151]

An interesting red herring is a borrowed neutral will show up as phase->cpc reversal if you plug it into the circuit the neutral is borrowed from and achieve DP isolation on that circuit (providing there is a load connected it to it)

The reason why is that the borrowed neutral will drag the neutral to 240v, the phase will be dragged to 240v through any load on the circuit

The tester then sees:

240v between cpc and phase
240 between cpc and neutral
'not much' between phase and neutral

...

All that is in the tester is a few resisters and neons btw

 

[plugwash]

A broken neutral will also show up as a live-earth reversal.

As others have said theese are good as a quick test for the most gross of faults but no substitute for proper inspection and testing.