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I have a confusion about the topology below:

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I was wondering the potential difference between the line and earth. So I decided to check this through a 3-prong plug.

I thought I would read the same voltage as line to neutral, since neutral and earth are supposed to be connected.

But when I measure the voltage between the line and the earth, the voltmeter shows zero volts.

What does that mean?

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  • \$\begingroup\$ Can you clarify exactly where you are measuring at the wall socket or the appliance plug. \$\endgroup\$ – RoyC Dec 29 '16 at 11:29
  • \$\begingroup\$ @RoyC . I wasn't pushing forward enough the voltmeter probes right way. There is actually line to earth voltage now \$\endgroup\$ – user1245 Dec 29 '16 at 11:49
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If you are measuring 0V between the hot/line pin and ground, you either have a big problem or are doing something wrong.

The most likely option is that you have your multimeter set to DC voltage rather than AC voltage which would result in the average DC level being measured which for an AC waveform is theoretically 0. You could also be measuring the wrong pins on the plug, but that I imagine is not the case.

The alternative is that your plug or house is incorrectly wired such that the neutral and hot/line pins are swapped over. In theory (from an electrical standpoint) this shouldn't cause a problem, but in practice and from a safety standpoint it is a big issue in devices which don't have an earth pin and assume that the neutral will be at earth potential.

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  • \$\begingroup\$ You were right. I wasn't pushing forward enough the voltmeter probes right way. There is actually line to earth voltage now \$\endgroup\$ – user1245 Dec 29 '16 at 11:49

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