AnsweredAssumed Answered

high resistance sensor measurement circuit

Question asked by sagi4422 on Jul 19, 2015
Latest reply on Sep 2, 2015 by AnnaFeB

Hi All,

I am a newbie in the field of electronics but have enthusiasm to learn and build.

I have a project I am involve in which needs from us to build a high-resistance sensor measurement system.

The sensor, because of the in-stability of fabrication, can have a baseline resistance between 10MOhm to 70MOhm.

The quest here is to measure the above resistance values and even expend it to 1MOhm to 70MOhm with  at least 5% of accuracy

The sensor frequency is very slow, <40Hz and it is operated on a battery of ~3/5V.

My request is to build a circuit that will measure the sensor's resistance and will have a range of measurement as described above.

 

I did some research in the Analog search engine and I didn't find the specific terms I am looking for but this is what I came so far:

 

Building a wheatstone bridge with 3 legs with 100MOhm. The 4th leg is the sensor. This gives me an output voltage range of 0.3V to 1.6V (if powered by 3.3V). Both output leads goes to a differential in-Amp (AD620) with high input impedance (20G). Vout due to its low current, goes to a unity-gain op-amp and than to an 12BIT ADC.

 

I was wondering whether I am in the right direction.

 

Any feedback is welcomed.

 

Sagi

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