Error in execute_io_action for pumping?

Software
1

Hello,
I’m using a turbidostat but when the time comes to pump and evacuate, something strange happens: I’ve set the volume pumped to 0.4 mL then first 0.4mL is added then 0.4 mL is pumped, but then 0.8mL is pumped again. It is a problem to keep the volume constant.
This happened not only in my personal turbidostat but also in the native turbidostat. It therefore seems to me that the problem may be with execute_io_action.
Four your information, my version is 24.3.10

Here is the log :

7.97 h pio1 dosing automation DilutionEvent: Latest OD = 1.10 ≥ Target OD = 1.10; cycled 0.80 mL
27.96 h pio1 dosing automation Removing 0.8 mL waste.
27.96 h pio1 dosing automation Removing 0.4 mL waste.
27.96 h pio1 dosing automation Adding 0.4 mL media.
27.96 h pio1 dosing automation Removing 0.8 mL waste.
27.96 h pio1 dosing automation Removing 0.4 mL waste.
27.95 h pio1 dosing automation Adding 0.4 mL media.

Update : even the native Chemostat has the same problem

2

Hi @elielD,

If you referring to the sequence:

add 0.4
remove 0.4
remove 0.8

This is by design. We run the waste pump an additional time (0.8) to make sure that any delta between the media pump and the waste pump is removed (a delta can accumulate and overflow the vial). If you want to remove this extra waste removal, you can change the parameter waste_removal_multiplier in your config.ini to a lower value. You can read more about the idea here.

The confusion might be caused by “Removing 0.8ml”, maybe it should say “Running remove-pump again for up to 0.8ml”

3

Ok, thank you very much for the explaination. I just would like to add that in the end, the vial was emptied : maybe it comes from a bad calibration of pumps then.

4

If the vial was emptied, it sounds like the efflux tube is too low. The efflux tube’s height determines the final culture volume (since the efflux can’t reach any liquid below itself!)

5

I understand ! Thank you very much !