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Pioreactor
[what happened] strange noise during experiment
Happened again, close to 3m periodicty. worker2 in experiment "Temperature Test 3"
Attached is the OD data. stirring and ir led reference looked fine during that time, too.
export_Temperature_test_3_1654182107.zip
Occurred again in worker2.
- restarted stirring twice. No effect.
- tried reducing the IR intensity (maybe the opamp was saturated) - no effect.
- relative IR seemed stable (and the log data shows very stable single)
- tried restarting OD reading, no effect. Turned on DEBUG, logs are attached.
- htop didn't show anything weird
- no under-voltage problems
- CPU temp seemed normal.
Lasted for about 2h:
Current theory is that is caused by CO2 bubbles.
- noise occurs after a period of a hours => critical amount of CO2 produced to form into bubbles. Also seemed to end when growth ended.
- occurred when using closed caps => not enough oxygen => fermentation route => more CO2
- tiny bubbles build up (trapped) in the center, and eventually enough do that they form into a large bubble and exit
- didn't occur in very tightly capped vials => CO2 remained dissolved in liquid
Solutions:
- allow for more oxygen transfer
- slower stirring RPM to not trap small bubbles in middle