eVOLVER Forum

Mid-experiment Noise in OD measurements

I ran a longer multi-day experiment and most of the vials preformed well, but something strange happened with vial 15 right after the 24 hour mark.

All vials run with LB + Tween20 0.5% (v/v) and different concentrations of carbenicillin (denoted in pink).


Close up OD measurements of vial 15:

Some helpful (?) notes: I took a sample just before the 24 hour time point, didn’t hear any strange noises from the stir bar, and topped off the vials media to 1L just before leaving for the night. We also have two OD sensors already for all the vials.

Do you have any recommendations for this? Or know what might be the cause?

Do you have the temperature trace around then? The dilution immediately prior to 24 h did not go all the way down, which makes me think there may have been a small leak or overflow. The thermistor is usually pretty sensitive to overflows and would get affected at the same time if that’s the case. If a drop/stream of media runs in front of the LED or photodiode, the signals could go crazy.

I’ve seen something similar when the influx straw was bumped and loosened a bit during sampling, causing a little fluid to leak out during each subsequent dilution.

@cmancuso The temperature sensors are as expected, just low temperatures when it tries to rapidly dilute.


I saw no trace of an overflow, but we do have a lot of dust and random debris falling down from the ceiling in that part of the lab. I did see a paint chip fly out when I blew air inside, so maybe it just happened to land in an unfortunate place.

Thanks for the advice!

That would certainly be a first! But at least it seems the sleeve is likely okay, so fingers crossed for your next experiment!