Piezo disk transducer

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.



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snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@y66g2000hsf.googlegroups.com:

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.

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snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@y66g2000hsf.googlegroups.com:

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.

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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.


-- Fermez le Bush--about two years to go.

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Salmon Egg

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 ..

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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.

Regards, Joerg

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excellent idea!


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