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Associate

Join Date: Jul 2006
Location: Austin, Texas
Posts: 45

How to test contact vibration sensors

12/08/2021 2:10 PM

Hi all.

I wonder if anybody can help me figure out a system to test the frequency response of an electro-dynamic contact vibration sensor.

Shape:cylindrical

Diameter 15 mm - Height 13 mm

Impedance: 500 ohm.

Mass; 6 grams

Frequency range: 60 Hz to 12 kHz.

Relative small amplitude of vibrations. I would like to avoid a commercial shaker.

So far I have been using a speaker playing a sine sweep with the sensor glued to the cone. I get a frequency response but how do I calibrate the rig?

Thank you all in advance!

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Pathfinder Tags: Sensors calibration response
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Guru

Join Date: Sep 2009
Posts: 1032
Good Answers: 86
#1

Re: How to test contact vibration sensors

12/08/2021 5:41 PM

Use a flat response mike in a sound pressure feedback servo loop to stabilize cone sound volume output and make your sweeps slow. Speaker should NOT be on an enclosure but on a relatively heavy flat panel and arrange for as anechoick conditions as possible on both sides. You can then make comparative measurements of sensor output. S.M.

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Associate

Join Date: Jul 2006
Location: Austin, Texas
Posts: 45
#2
In reply to #1

Re: How to test contact vibration sensors

12/08/2021 9:45 PM

Ok thanks. Yes, the speaker in not in an enclosure just like you said and I am using a flat diaphragm speaker from Tectonic.

https://www.parts-express.com/Tectonic-TEBM46C20N-4B-BMR-3-Full-Range-Speaker-4-297-2157

I have few mics around but I think I should buy a tiny condenser capsule from Primo.

Few questions:

Should I get a directional capsule? How far from the diaphragm would you place it?

Could you explain the servo loop? Can I just build one that can controls the amplitude of the (slow) sweep going to the amplifier?

Thank you so much.

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