Have you noticed liquid level detection not working when the volume in the container is too low?

General
1

have you noticed liquid level detection not working when the volume in the container is too low?

we have a container (well in PCR plate) with only a couple of microliters in it. LLD doesn’t work on those wells whereas it does on wells with a little more liquid

2

CLLD or PLLD

my rule of thumb for PCR bio rad plates is you need >80uL in the well for CLLD to be 100% accurate.

This is why Venus go to bottom error handling is a nice

3

cLLD

yes, I want to add something like this in PLR as well

4

its measuring capacitance (not completing a circuit) so its all up to the capacitance of liquid you’re measuring, the material of the plate, how that plates sits on the carrier (is it sitting on the skirt, or the pedestal), and how well your carrier is grounded to the STAR chassis. I wouldn’t expect it to detect few uL in a 96w pcr plate.

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5

We’ve run a few tests, and some instruments do better than others, but this also could be how well impregnated the graphite is in the tips… impossible to track down the variance

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6

Also the 96Head, not sure if you have one, but for some reason the standard Hamilton aspirate CLLD command only checks two channels when in reality the 96Head has 4 sensing channels:

If ur using a 96head you can get more accuracy by turning on more sensing channels

1 more post, but apparently they have guidelines in the STAR manual:

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7

Thanks @cwehrhan for the links and information!

I have updated the error message to reflect this knowledge.

8

I would say:

“No liquid level found (possibly because no or too little liquid was present to trigger cLLD)”,

I say this because it could confuse 70 and 71. Error 71 is “not enough liquid present” can be triggered two ways:

  1. surface following position - can’t go to the defined final position
  2. Immersion depth - not enough liquid present. It is comparing the calculated volume at that height returned to the volume requested to aspirate. You will often get this with meniscus effects and poorly defined labware. So in this case the robot truly thinks “too little liquid” to complete aspiration.
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9

:brain:

thank you

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