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testing zener diodes

Discussion in 'Electronic Basics' started by tempus fugit, Oct 28, 2003.

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  1. tempus fugit

    tempus fugit Guest

    Hey all;

    I'm trying to test a 5.4 volt zener in a piece of equipment I'm trying to
    fix. I've got a Fluke digital meter with a diode test on it. What should the
    reverse voltage reading be if it's good? I get around 0.6 in a forward test,
    but what should I get in the reverse reading (5.4v)?

  2. It should be the same reading you get with an open circuit. Most
    diode checkers apply less than 3 volts to an open circuit. You could
    apply a small current through the diode by hooking a 9 volt battery in
    series with a 1K resistor, and measure the diode voltage drop.
  3. Ross Mac

    Ross Mac Guest

    5.4 volt zeners are cheap...just swap it out....that's the crude
    way...or...if you can power up the circuit...measure the drop!..Not rocket
    surgery as they say in the Eggo comercial......good luck...Ross
  4. norm d.

    norm d. Guest

    A simple and reliable method to test a zener is to hook up a simple series
    circuit with a voltage a few volts more than the rating of the zener across
    the resistor and zener, with the zener in a reverse bias mode. Select the
    resistor to limit current to a value less than & no more than the forward
    current limit of the device. If the zener works it should force it's rated
    value across itself, and the remaining voltage should be dropped across your
    carefully selected resistor.
  5. John Fields

    John Fields Guest

    Well... No.

    Since the specified range of the voltage drop across the Zener is only
    specified with the _test_ current flowing through the Zener, that's what
    should be used.
  6. JeffM

    JeffM Guest

    A simple and reliable method to test a zener
    I notice that no one has yet said to
    disconnect one end of the zener from the circuit.
    A shunt path will distort your results
    and a short in the load will really screw you up.
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