Patent ID: 8307697

Claim:
A method for estimating the viscosity of a liquid in an aspirating or dispensing probe, comprising: measuring a reference pressure which is the pressure inside a metering tip when no dispense or aspirate is occurring (P ref ); dispensing or aspirating a liquid having a volume of air between the liquid and the pumping mechanism of the probe; stopping the aspirate or dispense; measuring the pressure (P stop ) inside the tip at a time (t) which is the time when the aspirate or dispense is stopped; measuring the pressure (P stop′ ) inside the tip at a time (t′) after t; calculating a relative pressure difference ( p ) which is the difference between P stop and P ref ; calculating the rate of pressure change ({dot over ( p ) at P stop by {dot over ( p =(P stop′ −P stop )/(t′−t); and estimating viscosity as a function of p and {dot over ( p .