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How to know wire polarity in an open circuit without any electrical power?

z234

Dear friends, thank you for all your kind help.

How to know wire polarity in an open circuit without any electrical power? E.g. you have a dashcam with 2 wires with same color insulation. How do you know which is positive and which is negative?

If you plug wires wrongly into the battery, a short circuit may happen and damage the dashcam.

How to test for wire polarity in this open circuit then?

Thank you very much 

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  • 0

    You measure *continuity* using the continuity/ohms setting on your multimeter to determine which of your two same coloured wires go to positive or negative.

    Alternatively, apply power to one side of the wire while the load is disconnected, using the multimeter in volts to determine polarity.

    The wire may be the same colour but also may have a subtle stripe down one side. This can indicate negative, but this is not universal.

    Otherwise, ask the manufacturer, or disassemble the device and test for continuity of the wire to a polarised component (e.g. the negative of an electrolytic capacitor on the input).

    - Gough

  • 0 in reply to Gough Lui

    Dearest Gough,

    I have followed ur advice n did a partial power on , without closing the circuit. I was able to detect polarity using a digital multimeter. Tq very much.

    How do u see the ohms which is positive or negative by testing continuity? Does the numbers of ohms determine POS or neg ? Tq very much

  • 0 in reply to z234
    z234 said:
    How do u see the ohms which is positive or negative by testing continuity? Does the numbers of ohms determine POS or neg ?

    Ohms can only be positive value. The range is from 0 to infinity.

    Gough suggested to measure, with a continuity meter, which wire goes to the + point of the circuit. And which wire to the - point. You would put one probe on a known + or - point. Then touch one wire with the other probe. The one that shows continuity is connected to that point. The other wire is then the oposite one.

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  • 0 in reply to z234
    z234 said:
    How do u see the ohms which is positive or negative by testing continuity? Does the numbers of ohms determine POS or neg ?

    Ohms can only be positive value. The range is from 0 to infinity.

    Gough suggested to measure, with a continuity meter, which wire goes to the + point of the circuit. And which wire to the - point. You would put one probe on a known + or - point. Then touch one wire with the other probe. The one that shows continuity is connected to that point. The other wire is then the oposite one.

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