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>I have had a post by Ken Sallot copied to me regarding using a digtal = >voltmeter to measure the output of an Oxygen cell. Some simple = >calculation was then done on the o/p voltage given to convert it to an = >O2 concentration. All this, of course, was done following the usual = >calibration procedures. > >I have a couple of questions regarding this. >1) How linear is the o/p from these cells? >2) Has anyone done the calculations electronically, ie used an amplifier = >to boost the o/p. eg the 11.7mv reading given in the example to 21( = >20.9) mv >for air. ( Other than in a proper O2 meter of course.) I bought a ICL7106 based millivolt meter for about $25.00CDN. There is one resistor on the board that needs to be replaced ($0.05CDN) and then the circuit can be calibrated in PO2. The thermal stability of the circuit is fine but there is no temperature compensation for the sensor. I calibrated in air and then checked pure O2 with about 4% error at 100%. I was using a miniox sensor at the time. I still have some testing to do on this circuit but I expect that if the calibration gas ( air ) and the test gas ( say 36% O2 ) are reasonably close and the temperature of the sensor is constant you will get an accurate reading ( depending upon your definition of accurate ). Barrie
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