Measuring continuity and leakage of the same conductor using 2 voltages concurrently

Discussion in 'General Electronics Chat' started by strantor, Dec 8, 2010.

1. strantor Thread Starter AAC Fanatic!

Oct 3, 2010
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I wanted to know if it is possible to test a length of wire for continuity at a low voltage while at the same time testing the same piece of wire for leakage with a very high voltage. I conneceted the following circuit:
top right: my homemade continuity tester, 4AA batteries, 8.5K resistor, green 3mm LED
Left: a resistor to simulate a very long piece of wire

So, in position A with the megger unshorted, My LED would stay on, which is what I want. I want the wire charging at 1kv with the megger, while checking continuity with 4.5V.

In position B, My LED turned OFF, which is what I expected would happen, as the greater 1KV would see the opposing 4.5 V as a resistance in parallel with it and try to pass through it, being stopped by the diode.

So, my question(S) are:
.Is this really working for the reason that I think it's working, or is there something else going on here that I haven't accounted for.
.Does anything about this go against any written/unwritten rules for building circuits (or, plainly, is it a good circuit?)
. would this behave the same way if I were to replace the battery in the continuity tester with an ac/dc converter @6v?
\
Thanks!
Charlie

2. kubeek AAC Fanatic!

Sep 20, 2005
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You serisously expect to have 1000V AND 4.5V across the same two points at the same time?

Anyway, shouldn´t the megger show discontinuity by itself?

3. strantor Thread Starter AAC Fanatic!

Oct 3, 2010
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Across, no. you will only get the 1000v across those points if you are in position B, at which the 4.5V will stop at the diode (I think).
yes, in position A. In position B it should show resistance of the big resistor

4. thatoneguy AAC Fanatic!

Feb 19, 2009
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Any wire can have ONLY a single voltage value and a single current value at any given point.

5. kubeek AAC Fanatic!

Sep 20, 2005
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Strantor, you said
While means at the same time. Not possible.

6. strantor Thread Starter AAC Fanatic!

Oct 3, 2010
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Oh, sorry. What I meant was the live +1000v lead attached to the conductor, 0V lead attached to earth/case. No voltage passing, but waiting to pass if the conductor were to touch earth/case. I was misleading

7. timrobbins Active Member

Aug 29, 2009
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Yes that would be fine, as long as the two test circuits are completely independant and have only one point of interconnection.