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Piezo disk transducer

Discussion in 'Electronic Components' started by [email protected], Apr 1, 2007.

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  1. Guest

    Is there any easy way to test the resonance on a piezo disc
    transducer? I have a few and need to know the resonance before I use
    them in a circuit.

    Thanks

    Steve
     
  2. wrote in
    Resonance of a diaphragm is more a physical thing than electronic. If you
    can get it mounted in your intended case, assembled and filled as close to
    final result as you can easily get, you can test it.

    Two ways: One is to put a microphone close to it, wrap the head of the mic
    in a sock to damp all but the most immediate and direct signal path, then
    send a slow square wave with sharp edges into the sounder, record the
    microphone signal at the best sample rate you can get, and examine the
    overshoot of the waveform. The square won't make it through a DC blocker,
    but the overshoots will. Use plenty of mic gain, and avoid live feedback.

    Second way is esier but has more room for error, sweep the frequency of a
    sine wave with constant amplitude, and record the output as before, but
    there's no need to be as careful with the mic placement, you're just
    looking for peaks of higher amplitude. If you find a strong narrow one,
    look closely at it (Spectrum analyser in Sound Forge or GoldWave or Cool
    Edit) to get the frequency.
     
  3. wrote in
    Maybe an even simpler way, but you still need to mount it as intended, as
    that will determine the frequency you'll get. When mounted, wire it
    directly to an audio input and tap it gently with a light but hard object,
    so that you're simulating a very short strong undamped pulse. Adjust the
    gain for good level, then examine the response in the recorded waveform.
     
  4. Salmon Egg

    Salmon Egg Guest

    What frequencies are you interested in. If you have an ac bridge that will
    work in the frequencies you are talking about, you can measure the impedance
    at the frequencies of interest.

    Also, try hitting the disk with an impulse and look at the response on an
    oscilloscope. It should ring at the resonant frequency. It may be a bit
    tricky to couple to it properly, but after all we cannot do it for you. You
    also might have to use slightly different technique for series and parallel
    resonances.

    Bill
    -- Fermez le Bush--about two years to go.
     
  5. Werty

    Werty Guest

    Put into a real circuit that does
    somethin real ..

    Input a tiny drive signal
    and measure the DC amps
    going into your driver ..

    At around 50khz , you will see it absorb

    very little power at its lowest harmonic .


    ---------------------------------------

    Then buy a MFJ209 ( 2 -170MHZ RF Bridge )

    and make a "dipper" and try same thing

    on R.F. circuit components , and

    get a fast electronics education .

    Its the best way to "see" whats happening .


    HAM RADIO magazine had an article
    about changing RF bridge into a
    grid Dip Oscillator ( "Dipper")

    Its just a coil , resistor and Cap , that
    makes MFJ209 read 3:1 SWR , over the
    band /range .

    I use mine handily ..
     
  6. Joerg

    Joerg Guest

    Metallize both sides if they aren't already. Conductive spray might
    work. Then place a resistor in series (1k or so to ground), hook a scope
    across that resistor and sweep it through with a generator.
     
  7. LVMarc

    LVMarc Guest

    excellent idea!

    Marc
     
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