Problem DO Sensor (signal degrades/ goes out of calibration over time)
Account cancelled 2019-07-22 17:15:25 2215 Views2 Replies RE: Gravity: Analog Dissolved Oxygen Sensor / Meter Kit
I have 2 oxygen uptake rate reactors running in parallel with the airation being controlled by the DO sensors. The signal degrades which means that what was originally calibrated to read eg. 80% oxygen, is only reading 60% oxygen, which is not ideal as the airation is supposed to switch off at 80%, so my reactors are getting saturated.
The probes are correctly calibrated when being put into the reactor and read the correct values to start with. I have an old probe (that unfortunately can't be used to control the system) which I spot check the DO levels with, which is how I now that the probes are out of calibration (and I have calibrated the old probe each time to make sure it isn't that one which is off).
I have already gone through the standard troubleshoots of fresh electrolyte, fresh membranes etc. I've also used ptfe tape to better seal the caps so that nothing is leaking in/out.
I will point out that the reactors are running dirty water (sewage) however this is fresh so there is no hydrogen sulphide. The reactor only needs to run for 48h and I'm happy putting fresh electrolyte and membranes on for each run, but I could do with it working.
Does anyone have any suggestion? It must be a systematic error (rather than both probes being dodgy) as both probes are losing calibration (though not at the same rate).
I have 2 oxygen uptake rate reactors running in parallel with the airation being controlled by the DO sensors. The signal degrades which means that what was originally calibrated to read eg. 80% oxygen, is only reading 60% oxygen, which is not ideal as the airation is supposed to switch off at 80%, so my reactors are getting saturated.
The probes are correctly calibrated when being put into the reactor and read the correct values to start with. I have an old probe (that unfortunately can't be used to control the system) which I spot check the DO levels with, which is how I now that the probes are out of calibration (and I have calibrated the old probe each time to make sure it isn't that one which is off).
I have already gone through the standard troubleshoots of fresh electrolyte, fresh membranes etc. I've also used ptfe tape to better seal the caps so that nothing is leaking in/out.
I will point out that the reactors are running dirty water (sewage) however this is fresh so there is no hydrogen sulphide. The reactor only needs to run for 48h and I'm happy putting fresh electrolyte and membranes on for each run, but I could do with it working.
Does anyone have any suggestion? It must be a systematic error (rather than both probes being dodgy) as both probes are losing calibration (though not at the same rate).
2019-09-12 19:05:25 Do you stir the probe when measuring? The DO probe will consume the oxygen in the liquid, so the probe needs to be stirred. 
Youyou
Youyou 