Cookies help us deliver our services. By using our services, you agree to our use of cookies. More information

Oxygen sensor test

From Bioblast
Revision as of 13:26, 31 August 2010 by Fasching Mario (talk | contribs) (split of "topics")

The Sensor test is The Main Tool for Troubleshooting. It should be done

- whenever a problem is encountered

- when the performance of the instruments is doubtfull

- from time to time for Quality Assurance

- after a sensor service or after applying new membranes

- during the trouble shooting procedure by switching components a sensor service is done after each switching step.


After a sensor service or after changing membranes the oxygraph should run (i.e. the oxygraph, stirring, etc is switched on) over night (chambers with EtOH/water or just water) before a sensor test is performed or other experiments are started. This ensures proper stabilization of the signal. It is of advantage to follow the sensor test by observing the Raw Signal.


How to do a Sensor Test:

- fill with water

- set T = 37 Β°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 Β΅l 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 case another injection of dithionite 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"


Evaluation of a Sensor Test

Most parameters are best viewed by observing the Raw Signal.

Infromation gained by the sensor test include:

Raw Signal at air saturation

Signal stability at air saturation

Flux at open chamber

Response time of the sensor

Flux at closed chamber near to air saturation

Raw signal at zero oxygen (zero current)

Signal stability at zero oxygen



Template:Troubleshooting

... more about "Oxygen sensor test"
sensor +  and performance test +