Piezo disk as Vibration Sensor: input buffer and filter

RE: Piezo disk as Vibration Sensor: input buffer and filter

Jan Cumps — Tue, 25 Jun 2024 09:29:18 GMT

[mention:a5312e9762dd4699ba5d3876da34ffe5:e9ed411860ed4f2ba0265705b8793d05] , the charge amp white paper link throws a 404: not found error. Did it move?

RE: Piezo disk as Vibration Sensor: input buffer and filter

Jan Cumps — Sat, 24 Dec 2022 20:18:41 GMT

Food for a next post: How do I measure this circuit?

[mention:a5312e9762dd4699ba5d3876da34ffe5:e9ed411860ed4f2ba0265705b8793d05] has specified in that, to have a gain of 1, the feedback capacitor has to be the same as the capacitance of the piezo sensor at the input.

It was easy for me to measure the capacitance of the piezo disk with and LRC meter, and adapt the circuit to that. But in a test setup, I want to replace the piezo disk by a (programmable) function generator. To do tests across frequencies and amplitudes.

Do I calculate (maybe from the datasheet?) the impedance of my function generator? Then either put capacitors in series or parallel to match the impedance of the feedback capacitor?
Do I calculate that same value, then replace the cap in the feedback circuit with one that matches my test circuit? (and is that relevant?)

This circuit is based on capacities - it's a charge amplifier - so I have to deal with capacitance.

Thoughts?

RE: Piezo disk as Vibration Sensor: input buffer and filter

rscasny — Fri, 23 Dec 2022 14:24:55 GMT

This stopped me in my tracks. Wow. Thanks for doing.

RE: Piezo disk as Vibration Sensor: input buffer and filter

dougw — Sun, 18 Dec 2022 14:39:39 GMT

Nice PCB. Great result.

RE: Piezo disk as Vibration Sensor: input buffer and filter

javagoza — Sun, 18 Dec 2022 09:36:53 GMT

Great educational pill for a Sunday morning. Thanks for sharing!

RE: Piezo disk as Vibration Sensor: input buffer and filter

genebren — Sat, 17 Dec 2022 18:50:01 GMT

Very cool idea! I have a bunch of piezo disks that I will have to dig up and give this a try. Thanks for sharing!

RE: Piezo disk as Vibration Sensor: input buffer and filter

shabaz — Sat, 17 Dec 2022 18:46:26 GMT

Hi Jan,

Nice work! Very interesting to see the signal comparison between the $$$ device, and the piezo disk + amplifier. That's a very nice board. I have a load of piezo disks (for a kids project), I will add this board layout to the next PCB factory order to try out.