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metal-oxide varistors



  • Michael Harvey

    MOV are usually found close to high voltage main supply filter protection. They are designed to go into low resistance to guard against a voltage pike. Using your low voltage meter, it should look like a open circuit. Refer to the manufactures details (using the numbers on the side of the device) to determine the trigger voltage when the device will start to lower the resistance.

    If you are using recovered (2nd hand) MOV then one that tests as open circuit is good. When they fail (or have done more than what they should) they will usually blow up, splitting the side, letting the manufactured smoke out, or cracking the case. A failed one (split busted smoked) may still test as open circuit busted, just do a visual.

    If you really REALLY want to test the MOV, you will need a light bulb in series with the high voltage supply that exceeds the trigger point. As the voltage rises above the trigger point, current will flow through the light bulb. Warning, I advise against this as there will be dangerous voltages.


  • faidul islam

    if you measure using resistance mode and show short or low value resistance that's means short


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