(Topic ID: 2315)

Diode Test Question


By SealClubber

9 years ago



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  • 6 posts
  • 5 Pinsiders participating
  • Latest reply 9 years ago by thokennedy
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    #1 9 years ago

    I have a coil which is not connected to anything. I tested the ohms and it reads 5.8. I tested the diode and it failed. I cut it from the coil and the diode tested good. I put a new good diode onto the coil and now the new diode tests bad. The coil still has 5.8 ohms at the lugs. What would cause this?

    #2 9 years ago

    Sounds like it's good to me.. The diodes have a forward voltage drop of around 0.7V.

    Doing a quick Google search I came up with this for you.. Might explain it a lot better than me.
    http://www.allaboutcircuits.com/vol_3/chpt_3/2.html

    #3 9 years ago

    In one direction the multimeter should read nil and the other direction it should read +- .5 But as soon as I connect the diode to the coil it reads about .007 in both directions.

    #4 9 years ago

    When testing a diode you need to lift at least one leg to remove it from the circuit.

    When you're testing it installed you're reading a voltage drop across the coil, not the diode.

    #5 9 years ago

    I always suggest like NoVarcade to lift one side. A coil depending on it's windings etc can mess up the ohmmeter test. I know it's a PIA to cut and resolder.

    I use a Huntron curver tracer instead of an ohmmeter. But it's not something hardly anyone has sitting around.

    This is the one I own:

    http://www.testequipmentconnection.com/specs/HUNTRON_2000.PDF

    #6 9 years ago

    NovArcade is right...need to de-attach one leg...which at that point you might as well just replace it.
    Novarcade - do you need to remove it when its on a switch to test it? For some reason I am thinking you don't...

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