What is labware calibration? Why should you do it?

A labware definition informs the robot about the geometry of a physical piece of labware. However once that labware is on the deck the robot will need to know (a) exactly where the wells are located (b) where the top and bottom of a well are. Hypothetically if the robot knows a labware’s geometry and where each slot in the deck is, it should be able to perfectly predict the location of each well. However in reality there can be slight variations in physical labware and how those labware fit into slots. Those slight variations do add up and can cause crashes or the robot to miss wells entirely. 

If you calibrate labware in one slot that calibration data is applied to all slots that labware exists in. This will affect your protocol if you’re using multiple of the same labware, but some are at different heights than others. For example this would occur if you are keeping one of your plates on a cold aluminum block. You can get around this by using a custom labware definition for your plates that are elevated. 

When should you calibrate labware?

Calibrate labware when you’re running a protocol for the first time. If the run went well then you do not need to calibrate again in order to run this protocol again. 

See Do I have to do pipette and labware calibration every time I upload a protocol? For more information

If someone else in your lab runs a different protocol with the same labware they may do a new calibration. This will overwrite the calibration for the labware that you previously saved. The current calibration status of the labware in each protocol is displayed in the app when the protocol is uploaded.

Is the problem your labware definition or calibration?

When troubleshooting a labware definition it’s helpful to think about what calibration is actually checking for and altering:

  1. Labware height- This is where the ‘top’ of a well is. The bottom of the well is labware height minus depth. 

  2. X & Y offset- This is where the ‘grid’ of your wells is located within a slot. 

Note that calibration does not account for mistakes in:

  1. Well size (diameter, length x width, depth)

  2. Spacing between wells

If you are calibrating carefully and the robot is still missing wells or crashing we recommend you double check that the measurements in the labware definition actually match your labware. You can find all the measurements for labware in our API via the Labware Library. If you’re confident your physical labware and the definition are a match please contact support@opentrons.com for further help in troubleshooting. 

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