The temperature at which a liquid becomes semi-solid is deduced through pressure analysis of samples cooled to precise temperature intervals.
The low mass measuring cell traps a small amount of the sample, which is then cooled at a controlled rate. At pre-set temperature intervals the sample is micro-pulsed by a piston driven by a stepper motor. Sample movement is detected by a differential pressure sensor connected across the measuring cell.
Cooling is continued until the applied pressure pulse generates a positive differential pressure indicating that the sample is no longer moving; this temperature is taken as the no-flow point. The old sample is then warmed and flushed away and the cycle is repeated.