These equilibration experiments confirmed in microgravity the present understanding of the two-part equilibration process, which follows a change in a fluid's temperature when it is near T c . Almost all the temperature change is rapidly transmitted throughout the fluid. Accounting for these small temperature differences is crucial for the success of a liquid-vapor critical point experiment in microgravity. As shown in figure 3, the heart of the viscom eter is a nickel screen 7 millimeters wide and 19 millimeters long and weighing less than 1 milligram. An oscillating electric field causes the screen to oscillate between pairs of electrodes.
Viscosity causes the xenon to resist the oscillator's motion.
Thus, the viscosity can be derived from the ratio between the oscillator's motion and the force applied to the oscillator. During normal operation, the viscometer dissipates much less than a billionth of a watt in the xenon. To measure viscosity, an oscillating voltage is applied to the viscometer's electrodes. The resulting movement of the oscillator is monitored by a sensitive capacitance bridge. Both the input and output waveforms are measured and stored on a hard disk drive.