Knowles BU-21771-000

Anyone has success in evaluation / taking readings from this Knowles BU-21771?

I connected the terminals as suggested in the data sheet, but the readings were not producing much variance regardless of any contact with vibration source or not.

Any additional documentation or circuitry alternatives or a sample code that worked for you would be appreciated!


What kind of output were you expecting? Working the numbers on the listed sensitivity suggests that one’s only going to see a bit less than 6 mV/g from the sensor itself, so a lot of measurement tools aren’t going to show much without some sort of amplification.

Before I actually record the sounds, was trying to read the analogue signal from the sensor.
I thought this device comes with built-in amplifier. I tried with and without external amplifier attached to it though. Still the signal values I was getting from the device didn’t change much when in contact with vibration source or not.

I was expecting 5-20 points of reading difference when attached to vibration source vs when not attached. I barely get 1 or 2 points reading difference.

Do you have any recommended tools for recording the voice as wav files, instead of analyzing the analogue readings?

Hello Ravijo, I think some more context may help in devising a response to this.

Is the vibration operating in the 20Hz-10kHz range?
Is the vibration physically connected to the BU-21771-000? (no air gaps)

Any notes you are willing to share on your setup besides may also help in deducing possible troubleshooting paths.

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