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  1. #1
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    how to test mosfet

    Anyone can shown me how to test a Power MOSFET using Multimeter alter it is in good condition or faulty?

    Regards,
    Keng Loong, Liew

    •   Alt29th November 2005, 04:21

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    power mosfet testing

    MOSFET testing:
    http://www.4qd.co.uk/serv/mostest.html
    http://www.utm.edu/staff/leeb/mostest.htm
    Regards,
    IanP
    So: connect the meter negative to the MOSFET's source. This is arrowed in the drawing above which shows the most popular TO220 MOSFETs.

    Hold the MOSFET by the case or the tab if you wish, it doesn't matter if you touch the metal body but be careful not to touch the leads until you need to.

    First touch the meter positive on to the gate.

    Now move the positive meter probe to the drain. You should get a low reading. The MOSFET's gate capacitance has been charged up by the meter and the device is turned on.
    With the meter positive still connected to the drain, touch a finger between source and gate (and drain if you wish, it matters not). The gate will be discharged through your finger and the meter reading should go high, indicating a non-conducting device.



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    test mosfet multimeter

    I already follow the intruction of test, but why I can't get any reading when I used the function of test diod of multimeter? Even I used a new Power MOSFET, can you please give me a more clearer explaination?

    Regards,
    Keng Loong



    •   Alt6th December 2005, 11:25

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    how to test a power mosfet

    Your meter should be in "Diode testing" mode ..
    Most of general purpose digital multimeters will have the voltage of ≈3Vdc between (+) probe and (-) probe ..
    However, in some cases this 3V will be not enough to turn a MOSFET on ..
    Try to get (download) data sheet on a particular MOSFET and find out its Ugs(ON) ..
    If the Ugs(ON) is higher than 3V use a 9V battery (or as required) and 1MΩ resistor to "charge" the gate while measuring with a multimeter the resistance of the Drain-Source channel ..
    You should get a low reading. The MOSFET's gate capacitance has been charged up and the device is turned on.
    With the meter positive still connected to the drain and negative to the source,
    " ... touch a finger between source and gate. The gate will be discharged through your finger and the meter reading should go high, indicating a non-conducting device.
    The gate will be discharged through your finger and the meter reading should go high, indicating a non-conducting device."

    Regards,
    IanP


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  5. #5
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    mosfet testing with multimeter

    Attached please find the datasheet for the Power MOSFET STP60N06 and STP60NF06. It's declared that to on the MOSFET, input of VGS is minimal 2V, Typical 3V and maximum 4V.

    Why I still can't get a reading in my multimeter under DUT (diode under test) mode. For your information, my multimeter brand is SANWA CD800a. Is it suitable use to test this MOSFET?

    I don't think this MOSFET is not compatible with STP60NF06. Cause I can't find this STP60NF06, so I replaced this with STP60N06.



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    mosfet resistance test using multimeter

    According to STP60NF06 output characteristic (see pictures below) the Ugs(on) is closer to 4V than to 3V, and, as I mentioned before, most of multimeters will use as test voltage <3V.
    So this can be the reason why you can't open D-S channel of the STP ..
    Try to use a battery (9V) and resistor ..
    Regards,
    IanP


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    how to test a mosfet

    With your past experience, do you think that STP60NF06 can replace with STP60N06?

    What's happened to myself now is after replaced the STP60N06, the UPS is still not working. The battery of UPS still can't back up the power supply and indicated failed. What is the function of this Power MOSFET in UPS do you think? Is it work as Invertor to convert the +12VDC from battery to 240VAC?



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