![]() ![]() ![]() Here are questions, comments and recommendations of varying importance: Let me know if I can help with the hardware. I haven't looked at the rest of your list of opamps, but I suggest that you consider the MCP6V74 or similar - I've had good success with them for the low-noise audio applications. Looking at the datasheet, I'm pretty sure you'll run into an input common-mode voltage problem. I disagree that it is a good choice for 5V application. Your PDF schematics specifies the NE5534. I highly suggest the 16SoundsUSB as it uses more recent chips. With the information that the frequencies of interest do not span below the audible band, then I agree that the existing 8SoundsUSB and 16SoundsUSB acquisition boards can be used as-is. Regarding the frequencies of interest - I had (wrongly) assumed that your application would require sub-audible frequencies. I promise I'll look into the design further when the schematic seems OK and you have your own testing to back it. This inconsistency is what leads me to believe that the design in the pull request isn't quite ready yet. Seeing the design you used as inspiration, I understand now, that R1 is the biasing resistor and not in the sensing path. The original has a connection between the input of the amplifier (clamping diodes) and the piezo element, which is missing from the left schematics. I have no doubt that the original circuit works, however I believe a mistake happened when recopying it. There are no need to change the front-end, as it's intended for the human audio spectrum. OPA365,OPA1671,AD8613,TS922 and the one in the schematic. The circuit should work, as it is based on: Vincent R., hardware designer for the 16SoundsUSB and other have written you a email, I hope it doesn't end up in a spam filter. In addition to the transducer frontend, I think some validations and modifications will have to be made to the 8Sounds and 16Sounds in order to work at the low frequencies. I recommend you ground it through a 0603 package, 0-ohm resistor. Otherwise, the floating input could contribute to noise. I think J1-pin 3 should be grounded if differential configuration is not necessary. R1, R2 and R3 give strong attenuation to X1 output is the gain of 10 from U1 sufficient? I believe output of R1 should make its way to pin 3 of U1 for any amplification to be possible. Has the circuit been tested and shown functional? I have looked at the PDF schematics and recommended not to pull this project for now. The speed of sound in water increases with increasing pressure, temperature and salinity. They should be compatible with Manyears or ODAS.Īpproximate values for fresh water and seawater, respectively, at surface pressure are 1450 around 1500 m/s. If the piezo electric crystals are a suitable distance and 45° degrees apart from each other in a flat circular array with 8 piezoelectric sensors, NOAA technical memorandum NMFS 2008NOAA-TM-NMFS-SWFSC-417 also known asĪ guide to constructing hydrophones and hydrophone arrays for monitoringmarine mammal vocalizations,ĭescribes how to build a single crystal hydrophone. PZT-5 also known as SensorTech BM500,Channel 5500,Morgan PZT5A1 is widely used. The best piezoelectric sensors for listening is based on Aluminum Nitride and molybdenum. ![]() This circuit acts as a impedance buffer, and some amplification does not hurt as long as it is around 40dB. When wired to a normal 50 kilohm line input this forms a 200Hz high-pass filter, which eliminates the bass.īecause the piezo disc has a very high impedance (1 MΩ typical), it should be buffered to avoid possible impedance mismatch with an existing audio system. The reason why these devices often sound tinny is because the piezo sensor presents its signal through a series capacitance which is small, typically 15nF or less. The problem with piezoelectric and contact mics is that they are not well matched to typical audio inputs. ![]()
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