Discuss Voltage testers - a basic question in the UK Electrical Forum area at ElectriciansForums.net
Hi. As part of safe isolation we use a voltage tester to prove dead; I've been taught that this is done by putting the probes in the following combinations: N+L, N+E, E+L.
But why check anything apart from the Live? That's where the voltage is coming from right?
Ok but still, why test between 2 conductors? Why not test each individually?Assume every conductor is live until proved otherwise.
You can't reliably test one conductor without a reference.Ok but still, why test between 2 conductors? Why not test each individually?
This sounds good but I don't really understand. Can you point me to a resource with a fuller explanation please? I have spent most of the evening looking online but just can't find itYou can't reliably test one conductor without a reference.
What is the part that you can't understand ?This sounds good but I don't really understand. Can you point me to a resource with a fuller explanation please? I have spent most of the evening looking online but just can't find it
Thanks for this, fortunately I am familiar with the process itself but what I am stuck on is if we need to check that there is no voltage potential in each conductor why a tester couldn't be designed that you simply put on the end of the conductor (like a voltage pen but I understand they are not considered reliable enough)? So in your explanation above I don't understand "without a reference".What is the part that you can't understand ?
This explains a bit.
Safe Isolation Procedure - A Thorough Step By Step Guide. - Kewtech
Safe isolation is a task that needs to be undertaken for the safety of persons working on electrical installations and others who may be impacted by the process.www.kewtechcorp.com
When you do a voltage test the test instrument is checking is there a "pressure" difference between that point and another point. When it is testing the pressure difference a very tiny current has to "flow" in the test instrument. To allow the test current to flow it is a two pole device and thus needs two connections. This is also why you need to be able to prove the tester works before and after any proving dead tests, this needs either a proving device or a known live that is still live such as the supply side of the main switch.Thanks for this, fortunately I am familiar with the process itself but what I am stuck on is if we need to check that there is no voltage potential in each conductor why a tester couldn't be designed that you simply put on the end of the conductor (like a voltage pen but I understand they are not considered reliable enough)? So in your explanation above I don't understand "without a reference".
As a few others have already said, what you measure is voltage difference. The good example from above is a battery, it will do nothing unless you have contact to both terminals.Ok but still, why test between 2 conductors? Why not test each individually?
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