OD oscillating, even with no sample


Has anyone encountered oscillations in their OD readings, even in empty smart sleeves? Any ideas why? We tried covering the sleeves with foil, in case it was caused by ambient light, but that did not stop the oscillations. Our calibration plots looked good, and included both 90 and 135 degree photodiodes.

These sleeves had empty glass vials:

These sleeves had cultures, but not all grew:

Thank you!

Hm do you still see these spikes with stirring OFF? This is strange and I haven’t seen this before. Can you show your OD90 and OD 135 calibration curves?

Yes, I saw the spikes without a stir bar. I think the oscillations might be ambient light from a south facing window nearby. I am going to try a darker location for the eVOLVER today to see if that helps.
My 3D calibration curve is below for now. I will see if I can get the OD90 and OD135 curves to send too.


By closing the shade of the bright south facing window, the oscillations disappeared. I wanted to share the update in case other folks run into this issue. It is nice when the solution is so simple.

Thank you,


Amazing! Thanks for the update.