Belt Tension meter

Other Hardware General Electronics
1

i want to build a belt tension meter that measures timing belt tensions commercial meters are available however are prohibitively expensive the basis on how one of the commercial meters sensors works is two acoustic sensors are held over the belt on opposing sides of the belt and the sensors pick up on the vibrations which is converted into an electrical signal and is then processed through a subtractor in order to eliminate ambient noise from the signal however i am not sure what components i would need to use (i.e ultrasoninc sensor or microphone and the type of subtractor) the other thing is it will need to be processed and the output sent to an lcd screen in Hz.

Any help is appreciated and attached is the sensor diagram from the commercial meter's website

Clavis sensor head.jpg

2

Probably belts vibrate at quite low freguencies. Therefore you need microphones capable to detect low frequencies, such as сondenser microphone or (much-much cheaper) electret microphone, see Microphone - Wikipedia

"Subtracor" is trivial. For example, invert signal from one microphone and adds it to the signal from another microphone.

3

An opamp in differential amplifier configuration (ac coupled or band-pass) would be my way.
The signal processing probably involves either FFT, FDCT or some cosine resonators to pick out the
strongest frequency of vibration. I'd expect quite a lot of noise in the signal.