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AD7745 Capacitive Input Range Extension Circuit

Question asked by hassan.hariri@usherbrooke.ca on Apr 1, 2014
Latest reply on Apr 2, 2014 by seanbrown

Hello,

 

My capacitive sensor has an initial capacitive C0 of 20pF and a capacitance range of +-13pF when subjected to a tensile strain.

I was looking for a capacitive sensing circuit able to detect a small change of 0.12pF and able to measure capacitance in the range of 20pF+-13pF (for my capacitive sensor S1)

 

I found that the AD7745 able to do this task by using an extender circuit as mention in the link below

http://www.analog.com/en/circuits-from-the-lab/CN0129/vc.html

 

Is this method is the only solution or we can find another analog device circuit able to do this task without an extender circuit???

 

Can I have a capacitive sensing circuit able to measure capacitance in the range of 7nF+-4nF and able to detect a change of 35pF (for my capacitive sensor S2)??

 

The best choice is to find one capacitive sensing circuit for both capacitive sensors (S1 & S2). Is that possible?

 

Best regards,

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