This article is about the OT-One.

It's no-longer sold or actively supported by Opentrons, but we've kept this article here to help existing users. Please see our OT-2 Support articles for the most up to date information!


In some cases, users have encountered the inability to complete calibration of the labware for their protocol within the app. This is error occasionally occurs when the calibration pattern of the pipette's decimal places match that of the API. To correct this error follow the following procedure:


Inside the app, click ‘File’ at the top bar, and then click ‘Open Containers Folder’. From this folder, back track one directory to the 'Calibrations Folder' you will be able to find the calibrations .json file.

Open the .json file in your preferred text editor. We suggest Sublime Text 3.

You will see plunger positions similar to:

"a:p200": {
            "positions": {
                "drop_tip": 28.0101,
                "blow_out": 27.0101,
                "bottom": 23.0101,
                "top": 8.0101

Notice the .0101 at the end of each position. The default plunger positions also have this pattern (from Pipetteline 119):

default_positions = {
        'top': 0.0101,
        'bottom': 10.0101,
        'blow_out': 12.0101,
        'drop_tip': 14.0101

Then, inside opentrons.utils.state.are_instrument_positions_calibrated(), line 70 searches for that 0101 pattern to determine if a plunger is calibrated correctly.

return not any([
    str(val).endswith('.0101') for val in positions.values()

There is a backstory to this and why it was added to the 2.5.x release, essentially it is used to handle edge cases when calibrating pipette.

What seems to be happening here is that somehow these default values are being inadvertently sent as coordinates to the smoothie board. Then while jogging the plunger with 1mm steps, then the 0101 decimal place will stay.


Round all calibrated plunger positions to one decimal place within your . calibration file. This will guarantee removal of those added decimal places because the interface's jogging steps go down to 0.1mm at the smallest. 


Recalibrate the pipette's plunger positions using the .1mm step and the 2mm step until you receive the last check mark.

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