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- 27 Jan 2008
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Many power supplies use fig of 8 plug so line and neutral can be swapped. So there is no direct link to either live wire. But there will be some capacitive and/or inductive linking so a valve volt meter (draws no current) will show a voltage to earth.
The problem is finding a reliable earth. For that matter also a neutral. And John Wards tests with the bulb, relies on something to measure against.
Where the non contact voltage tester and neon screwdriver use your body as an aerial to compare against. And I note with my non contact voltage tester it works better if I am holding it, and it will show the laptop as live.
But in some ways safer as it does not rely on a good earth or neutral, so best to use both types of tester. Or in my case both functions of the same tester.
The problem is finding a reliable earth. For that matter also a neutral. And John Wards tests with the bulb, relies on something to measure against.
Where the non contact voltage tester and neon screwdriver use your body as an aerial to compare against. And I note with my non contact voltage tester it works better if I am holding it, and it will show the laptop as live.
But in some ways safer as it does not rely on a good earth or neutral, so best to use both types of tester. Or in my case both functions of the same tester.
