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Topic Title: Is there a Test Device out there?
Topic Summary: That can prove earth continuity
Created On: 13 October 2013 06:13 AM
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 13 October 2013 06:13 AM
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keithredpath

Posts: 424
Joined: 30 March 2002

Is there a high tech or low tech device out there that can prove earth continuity on metallic parts?

I am looking for a device, probably in the form of a Volt Stick or a Screw Driver, which will "Beep" when detecting an earth continuity.

This device should be adjustable so that it detects an earth continuity of less than one, two, three, four or five Ohms.

It would be used to prove the electrical safety of exposed metallic parts i.e. Electrical equipment and accessories without the use of a "Wander Lead".

Is there a Boffin out there who can make one?

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keithredpath
 13 October 2013 09:55 AM
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Legh

Posts: 3498
Joined: 17 December 2004

Well, it would have to be able to detect a potential difference. This is usually achieved by a voltage indicator with two probes.
Needless to say excluding a neon screwdriver which uses you as an extraneous conductive part to provide the return circuit, albeit of minute amps.
Other devices use something akin to a proximity sensor, detecting the electromagnetic/static field.

If you want an Ohms output then a loop tester, without the test button, with a wander lead, but then you're back to where you started .

I think it might be possible to make a non-invasive single probe instrument that could detect a voltage and provide an Ohms output. by converting the output gained through a proximity sensor and then through you as a known resistor to provide a simulated volt drop and an Ohms output.
One problem would be calibration and the other would be referencing the test circuit to an accessible conductive part such as a screw head. via your finger. Not something I would be willing to attempt, particularly if the screw head was at an undefined voltage !.

Legh

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Edited: 13 October 2013 at 10:23 AM by Legh
 14 October 2013 09:21 AM
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christait

Posts: 30
Joined: 08 February 2013

A Megger DET24C might work if you can find somewhere to clip it onto.
 14 October 2013 01:32 PM
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timothyboler

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Well to state the obvious, the concept of continuity means a low resistance path from point A to point B. Assuming you mean to measure from a metallic part (A) there lies a difficulty as to whether the (B) you are measuring to is 'true earth' or a reference earth such as the main earthing terminal of an installation, which may not always be at exactly true earth.

Therefore I'm not sure there is an accurate way to do it without a long lead. Only way I can think of is some kind of charge leakage measurement where you apply static charge to a metal object and see how fast it discharges to earth (probably wouldn't be very accurate though).

Regards, Tim

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 14 October 2013 10:32 PM
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sparkingchip

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Battery, bell and a length of wire
 20 October 2013 12:11 PM
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tomgunn

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Originally posted by: sparkingchip

Battery, bell and a length of wire


Ahhh... those were the days! And a wind up 500v megger.

Tom

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