During a protocol run, when the pipettes move to labware, you might notice:

  • One pipette goes to the correct place.

  • The other pipette is up to 1-2 mm off, and that error is consistent throughout the protocol.

Why this happens

This is a known limitation in software versions earlier than 4.0.0.

On the OT-2, labware is only calibrated with one pipette. To move the other pipette to the same position, the OT-2 relies on knowing the exact offset between the two pipettes' tips. It measures this with pipette offset calibration. (See How calibration works on the OT-2.)

Before software version 4.0.0, the OT-2 took that measurement by automatically tapping its pipettes against five tip probe switches hidden under the OT-2's trash bin. This could be inaccurate and imprecise. So, whichever pipette you didn't calibrate labware with would be slightly off-position when it moved to that labware during your protocol.

How to fix it

Update your Opentrons App and OT-2 to the latest software version. In v4.0.0, we improved how calibration works to make it more accurate, make it more precise, and fix problems like this.

If you still see this problem after updating, reach out to Opentrons Support.

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