The hardest part of reading a liquid class from another lab is often not the physics but the vocabulary. What one vendor calls air transport volume another calls a trailing air gap, and a newcomer reading either can be forgiven for not knowing they are the same knob. A catalog that spans instruments only works if the terms line up, so here is a plain-language decoder for the parameters you will meet most often, and the other names they travel under.
The parameters that move liquid
These are the settings that determine how fast and how far liquid moves.
- Flow rate: the speed of the plunger, in microliters per second, during aspiration or dispense. Sometimes just called aspiration speed or dispense speed. Slower for viscous liquids, faster for water-like ones.
- Mix flow rate: the same idea, but for the plunger speed used when mixing in a well rather than transferring.
- Swap speed: how fast the tip is pulled out of the liquid, in millimeters per second. Often called retract speed. It matters because pulling out too fast or too slow changes what clings to the tip.
The parameters that manage air
An air column sits behind the liquid in a tip, and several parameters shape it.
- Air transport volume: a pocket of air aspirated after the liquid to hold it in during transport. This is the trailing air gap, sometimes abbreviated TAG.
- Blowout volume: air aspirated first and then pushed out at the end of the dispense to clear the last of the liquid. You may see it called the system trailing air gap, or STAG.
- Over-aspirate volume: a small excess drawn and immediately dispensed to compensate for liquid the tip retains. Elsewhere this is a conditioning volume.
The parameters that manage timing and endings
- Settling time: how long the tip pauses in the liquid after aspirating or dispensing, so the column can equalize. Simply called a delay in many systems.
- Stop flow rate: a dispense speed at which the dispense terminates abruptly, used to break off cleanly. Related to a break-off speed.
- Stop back volume: a volume aspirated again immediately after a dispense, to pull back a hanging drop.
- Clot retract height: how far the tip may rise while still detecting liquid, used to catch clots. Tied to exit signal detection.