Hello All!
Ive been working on a hydrophone design, working off a reference design by a man named Jules.
The piezo cylinder we are using can be found here:
https://www.steminc.com/PZT/en/piezo-ceramic-cylinder-26x22x13mm-43-khzThe design/build is posted here:
https://www.instructables.com/Hydrophone-Drop-Rigs/However here is the schematic:
![Screenshot-2024-03-31-at-4-28-11-PM" border="0](https://i.ibb.co/sgS7SB8/Screenshot-2024-03-31-at-4-28-11-PM.png)
Jules is using a OPA1642 as buffer circuit and is passing the signal straight into a high-end field recorder, however I can verify that connecting the aux cable to a laptop or phone aux in still works just fine.
The design has a few challenges, in the past hydrophones have been lost if they are "knocked" (agaisnt, say, the side of a boat) and an overvoltage seems to find its way into the OPA1642 inputs.
Also, there have been issues grounding the circuit in the water to remove "hum" from the signal (presumably, this 50/60hz noise induced from power lines).
I thought if I re-worked the design with an instrumentation amplifier I could really elimnate any common mode noise, perhaps amplify the signal even better, and provide some input over voltage protection:
![Screenshot-2024-03-31-at-4-28-32-PM" border="0](https://i.ibb.co/xL34jNC/Screenshot-2024-03-31-at-4-28-32-PM.png)
However, my design really works quite terribly. The input and output signal all seems within spec, however there is a terrible hiss/noise on the signal, and I had to use nearly the INA129s max amplification to hear anything.
Any ideas as to why this did not work as planned?
I thought this was going to be rather slick