How do i check if equipment is running on same phase?

May 3rd, 2009 | by DistanceRunner |
DR804 asked:


I’m having some grounding issues between some measurement equipment and the controlling PC. Talking with their tech support, they’ve asked me “Is the computer running on the same phase of the mains as the blue phase instrument power that runs the meter?” I’m still a novice at electricity and wondering how I go about answering this question. Do I have to hook up both to a oscilloscope and see if they are in phase?

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  1. 3 Responses to “How do i check if equipment is running on same phase?”

  2. By tatereatinmic on May 5, 2009 | Reply

    oscilloscope is definitely the way to go
    in phase just means that the two ac signals will peak and valley with each other
    they should be the same frequency to even be in phase

  3. By CDog on May 6, 2009 | Reply

    Well if it is 110-120v ac then one wire is hot and the other neutral, and dc voltage is pos and neg, you can check that with a toy motor to see which way it spins, it will reverse when polarity is changed

  4. By Iguana on May 7, 2009 | Reply

    With an AC voltmeter stick one probe in the same slot of each socket. If you read zero volts they are in phase. If you read 220 they are out of phase.

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