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On Tue, 26 Sep 1995, David Norton (Excell Data) wrote: > Do people have any preferences on Oxygen analyzers? > > Comments would be appreciated on the vandergraph, Teledyne and the Mini-ox. > > Does the DINKIT on the Vandergraph make analysis easier? > -- > Send mail for the `techdiver' mailing list to `techdiver@terra.net'. > Send subscription/archive requests to `techdiver-request@terra.net'. > The Vandergraf Analyser uses the Teledyne R17 O2 sensor. I have extensively tested a batch of 10 of these sensors, and found that they appear to be less linear than the sensors that came with the two Mini-Ox analysers I have access to. ie: If you "calibrate" on a known gas, they will give a slightly different calibration on another known gas. The spec-sheet on these sensors quote +/- 1% accuracy. In tests, I have found much greater errors with some of the units. The Mini-ox sensors seemed to be "spot-on" whether I calibrated on air, and tested O2, or vice-versa. Having said that, what sort of accuracy do you need for O2 analysis? And if you had an analyser that told you you had 79.8% O2 in your mix, would you do anything with the decimal place? A decent digital multimeter switched to mV, an O2 sensor and a calculator will be just as accurate as a purpose-built O2 analyser, although a lot less convenient, and an extra opportunity for errors. The Vandagraph quotes 0.1% "resolution". Notice they don't say "accuracy". One thing I have seen that influences accuracy and repeatability most, is the set-up for applying the test-gas to the sensor. While I haven't yet tested the Vandagraph DIN fitting, it seems a pretty brutal and "hit-or- miss way to apply gas to a sensor. Regards, Bernie Woolfrey
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