Oxygen sensor test

How to do a sensor test:

- fill with water

- set T = 37 °C

- set gain = 2

- set stirring = 750 rpm

- wait for thermal equilibration (use layout 1, watch for Peltier power % to get stable)

- with open chamber wait for stable signal

- air calibration (open chamber, stable signal = zero flux)

- closed chamber: stable, non-zero flux

- stirring test (switch off stirrer, wait, switch on stirrer, wait)

- zero calibration (dissolve a few crumbs of dithionite (= zero solution powder) in a drop of water, inject immediately 50 µl into the closed chamber, wait until most of the drop in oxygen concentration or raw voltage has occurred and then inject another portion to make sure that zero oxygen has really been reached. No stepwise drop should occur after the second injection otherwise oxygen has not been zero after the first injection. A second important criterion is to observe the (red) flux signal. At zero oxygen plus an excess of dithinite that consumes any oxygen diffusing into the solution the flux should be zero. However, especially with a rather slow sensor it may take some time to reach zero flux. The flux will in this case be positive and decreasing. It is not necessary in this case to wait for a complete zero flux for a simple sensor test. A negative flux on the other side strongly indicates that zero oxygen has not bee reached jet (all the ditionite has been consumed by oxygen, therefore the oxygen back diffusion is visible as a negative flux). In this another injection of dithinite is necessary.

Depending on the the version you have, a demo file with such an test is included on your CD under "5-Datlab-Download/DLDemo/DLDemo_troubleshooting"