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inductor tester

Discussion in 'Electronic Design' started by Michael, Dec 10, 2007.

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  1. Michael

    Michael Guest

    All one needs to know about an inductor may be found by applying
    voltage and monitoring current.
    I have been using this homemade gadget for a while: big ass MOSFET
    driven by an appropriate gate driver, 555 timer (with toggle switch to
    change ranges and trimpot for fine adjustment), low L shunt and bunch
    of caps to keep voltage stable. 3-rd year EE student could do it
    (IMHO). OK, one needs to know what s/he is doing as layout does
    matter. The problem: every time I drop the jig, I have to fix
    something as assembly leaves much to be desired. Well, not exactly,
    but it looks ugly.
    BOM (including PCB) should be between $5 and $20 (depending ob
    quantities), shouldn't it?
    Does anybody sell gadget like this?
    P.S.: It is taken for granted that a lab has oscilloscope and power
  2. D from BC

    D from BC Guest

    I test inductors with resonant circuits and square wave.
    I measure the resonant frequency on the scope.

    I can add a bias voltage to get core some core detail too.

    D from BC
  3. Tim Williams

    Tim Williams Guest


    When I only want to know the inductance, I resonate it with a cap and the
    signal generator via resistor.

    Some day I may build a full design, consisting of square wave oscillator,
    MOSFET switch and current sense resistor.

    If you really wanted to get interesting, you could make a free-running
    oscillator which turns on until the derivative of current change (i.e.,
    d^2I / dt^2) starts rising (saturation), then turn off for a time period
    corresponding to about 5-10 times the total on period (obtained via an
    integrator during that cycle).

    The rate of rise is sampled (with an analog S&H) and displayed on a meter,
    while the saturation point (which jointly determines frequency) is
    displayed on another range.

    Hey, that's not a bad idea.

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