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how to test optocoupler using multimeter?

Discussion in 'Troubleshooting and Repair' started by Zippora, Sep 14, 2016.

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  1. Zippora

    Zippora

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    Aug 26, 2016
    how to test transistor side of optocoupler using multimeter?
     
  2. Minder

    Minder

    2,955
    624
    Apr 24, 2015
    If it is the style where the base has a pin, check with the method usually used on the meter diode range.
    From base to C & E with reversing polarity of the meter.
    M.
     
  3. Zippora

    Zippora

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    Aug 26, 2016
    Thank you for the reply.
    It is 4 pin optocoupler. So only emitter and collector pin is out on transistor side.
     
  4. HellasTechn

    HellasTechn

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    212
    Apr 14, 2013
    if it uses a led then you can use the diode setting. again I don't know how to measure the transistor. if it uses a laser then I am not sure how either.
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

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    2,138
    Nov 17, 2011
    Use a battery and a series resistor to control the LED side (turn it on/off).
    Use a multimeter in Ω-range to check conduction of the transistor when LED is on, non-conduction when LED is off. That way you check the full photocoupler, not only one part of it.

    If you want/need to qualify the photocoupler in more detail, make the LED curent controllable (controlled current source) and wire the transistor side with load resistor and voltage source. Measure collector current as a function of LED current and compute the current transfer ration Ic/Iled.
    Get a datasheet for the photocoupler, these typically show recommended test setups for the component.
     
    Tha fios agaibh and HellasTechn like this.
  6. Zippora

    Zippora

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    Aug 26, 2016
    Thank you.
     
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