Hello all! I have lurked here for some time and figured I would finally post something. I am working on a project that requires an analog signal to be transmitted over copper for a very long distance ~500m. I have been referencing literature for telephone applications but really come up short on some good material and was hoping that someone here could point me to a good reference. To be specific, the signal is 28VPP 20mA max and the gauge wire used has to be minimal and so does shielding since space is at a premium for this application. Usually at these distances I would go straight to digital, fiber etc... but this must be an analog only operation. Sound fun right?!
Edit: I was expecting a reference, but you guys wanna get engaged.... should have known! Here are some more details..
Voltage signal
28VPP 20mA maximum
Signal of interest 1Hz-50kHz
Sampling 100kHz
Open field environment
Signal is from piezoelectric transducer, amplified by 40dB no filter
Specifics for signal loss are very unclear to me at the moment
Edit2:
Thank you for all of the information you all have contributed, very helpful! After some careful consideration I was able to work out the requirement for these to be all analog due to cost savings in the end. A balanced line configuration would have surely worked but with all of the custom connectors cable etc... it would have been quite costly. I was going to post this in a separate thread since it is a different approach but it seems to make sense to keep it all here for the meantime. I feel I should share more information about this specific application.All of these components will be in a tube that is about 70mmID and would need to house all of the transducers wiring etc.. spaced along the transducer section, not a lot of space to run a lot of analog wires. I can expect somewhere from 100-200 transducers. With this in mind I was going to use a small form factor DAQ to A/D the signals from the transducers in groups and use ethernet over coax to send down the line for processing. I was thinking something similar to this
https://labjack.com/products/t7 however all of these DAQs will need to share the same clock and it seems this product uses an external clock as a division from a local clock so it would not work in the end with the sampling delays, but just to show the idea. I would like to do a small demonstration to do a proof of concept for a larger one so for the small one I would do about 8 transducers and demonstrate both analog and digital. Any recommendation on small low cost daqs?