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Input Capacitance range extension  for AD7745

Question asked by Ben24 on May 11, 2015
Latest reply on May 14, 2015 by EricC



For a current project I am trying to measure the capacitance with the ad7745. The capacitance has a base capacitance of about 150 pF and changes approximately +/- 50 pF. A bit of googling led me to the circuit note CN-0129 . I build the circuit exactly as described in the circuit note and attached a fixed capacitance of 150 pF for testing.


I have the following problem:


I try to read out the I2C Bus with a Arduino Nano board. I'm able to read out the data and display it in the serial monitor, but I allways get a full range output.

How can I tell the Ad7745 that I use a range extension to read out the right values.


Does anyone of you have an example program for the arduino?


Thanks a lot, I hope anyone can help me.