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I have a piezoelectric sensor that I would like to use as a force sensor. Some rudimentary testing with it tells me that it is outputting voltages in the range of 0-120V VPP, possibly more (I haven't tested it all the way but the manufacturer tells me that it will output up to 150VRMS). A big issue here is a lack of information provided by the manufacturer (They don't really want to tell me more about the sensor)

I would like to use the readings from this force sensor as input to an ADC that is capable of handling 0-5V.

Some reading that I did seems to indicate that the following are possibilities that I can do:

  1. Voltage divider with op-amp buffer
  2. Voltage divider with op-amp buffer and a diode to clamp negative voltages

My question with regards to these two are: What type of opamp am I looking for for either one? These signals are very fast and seem to disperse very quickly. My issue with the diode to clamp negative voltages is that I don't see why this is necessary -- wouldn't you just treat one side of the piezo as COM and then the op amp would only see the peak to peak voltage?

My apologies if this sounds a bit rambling, I am rather new to electronics and do not quite understand how this works.

In addition, I would like to ask what op-amp would be good for this purpose?

Thank you

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  • \$\begingroup\$ A part number for your sensor would go a very long way. \$\endgroup\$ – Scott Seidman Feb 8 '18 at 14:28
  • \$\begingroup\$ There's no part number. It's from a manufacturer that doesn't want to disclose any information and only gave me very vague datasheets because they want me to buy their $30k system. You can try looking it up though, either under "Schwer + Kopka Discflex Sensor" or "Modular Communications Discflex Sensor". \$\endgroup\$ – Liria Feb 8 '18 at 16:25
  • \$\begingroup\$ If it is a piezo sensor, the output is a charge, and you will need to build a charge amplifier. Piezo sensors can only be used to measure dynamic force (change in force) and not static forces. You can read about charge amplifiers, but in general you will be able to manipulate the voltage range and frequency response by the resistive and capacitive load that you put on the charge output. \$\endgroup\$ – John Birckhead Feb 8 '18 at 23:07
  • \$\begingroup\$ Do you happen to have any guides or things to read about how the voltage and frequency response change when you change the resistive and capacitive load on the circuit? \$\endgroup\$ – Liria Feb 9 '18 at 12:56

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