If I have an open wire and a multimeter -- is there a way to check whether there is current and what voltage it is if the wire is not connected to anything, i.e. doesn't have another wire or an appliance to send the current to? Is there a common method whereby I can send the current to somewhere and then put the other probe of the multimeter there to simulate a circuit?
asked Jul 24, 2019 at 1:16
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There are some great tips on how to use multimeters with household voltage here: diy.stackexchange.com/questions/85575/…– kgutwinJul 24, 2019 at 1:47
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2Possible duplicate of AC common wire coming into thermostat low voltage– noybmanJul 24, 2019 at 2:19
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I flagged it as a duplicate even though this question could almost stand on its own. This question and this one: diy.stackexchange.com/questions/169767/… posted back to back are seemingly directly related. It might be helpful for us to answer the other question which contains this in it– noybmanJul 24, 2019 at 2:21
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Youtube probably has a video guide...– J CrosbyJul 24, 2019 at 14:10
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1 Answer
Two suggestions:
A non-contact voltage tester can detect line-level voltage without needing to complete a circuit. It does this by detecting the alternating electric field that radiates off any “live” household wire. It won’t detect direct current (uncommon in household settings) and will sometimes give false positive readings if the wire being tested isn’t grounded and is close to a live wire.
You can always use your multimeter in the AC Volts mode to test between an unknown wire and a ground. In the modern US, that means put one probe in the central U-shaped hole in the nearest outlet, and touch the other probe to the wire under test. This may also give false readings for the same reason as mentioned above.
By the way, the reason it’s valid to test voltage relative to ground is because that’s the test that matters to personal safety - if there is voltage relative to ground on a wire you touch, you could potentially complete the circuit with painful results!
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Beat me to it - I was still writing my answer (same 2 points, in the same sequence) when yours popped up. Jul 24, 2019 at 1:45
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As OP indicated in the question regarding current, it needs flow to be measured. I don't know that they were intending to only ask on DC; but as you've indicated, you can get the potential the line holds but now how much current it can deliver until A.) math on the "circuit" or B.) Completing the circuit, and completing it impacts current (AC and DC)– noybmanJul 24, 2019 at 1:52
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2I assumed the OP was using “current” in a colloquial rather than technical sense. Actually measuring household current with a multimeter is typically challenging...– kgutwinJul 24, 2019 at 1:54