A liquid class governs how a liquid moves, but it acts on a stage the instrument cannot see for itself. The robot only knows the deck you describe to it: where each piece of labware sits, how tall it is, how deep and what shape its wells are. Get those definitions wrong and even a perfect liquid class dispenses into the wrong place at the wrong height. Labware definitions and deck layout are the quiet foundation every transfer stands on.
What a labware definition encodes
A labware definition is a precise model of a piece of labware: its footprint and height, the position of each well, and each well depth, shape, and volume. The instrument uses it to compute where a tip must go and how far down to travel. If the definition says a well is deeper than it really is, the tip can crash into the bottom; if shallower, it can aspirate air.
Why heights and offsets matter to the class
Many liquid-class behaviors are expressed relative to the labware. Aspiration and dispense heights, submersion depth, and whether the tip follows the liquid down all assume the well geometry in the definition is correct. Level detection leans on it too, since the instrument expects the surface within a modeled range. A small offset error, a plate seated a millimeter off, or a definition that does not match the physical labware, quietly degrades transfers that the class itself got right.
Set it carefully, once
- Use an accurate definition for the exact labware you run, not a near-match, since well depth and shape differ between similar-looking plates.
- Calibrate labware offsets so the deck model matches physical reality before you trust heights.
- Re-check offsets after moving hardware or swapping labware lots.
- Treat the definition as part of the method: a class validated against one labware assumes that geometry.