Dielectric-insensitive capacitive differential pressure gauge for use at low temperature

A capacitive differential pressure gauge for use at temperatures below 4 K is described. Fluid is admitted to two sample chambers with flexible walls to which a sensing capacitor is mechanically connected. Differential pressu res between the chambers flex these walls and change the capacitance of the gauge. Because the capacitor is located outside these chambers, the gauge is insensitive to the dielectric variations of the fluid. Typical different ial pressures of 10(5) Pa were measured with a common mode rejection ratio in excess of 50. (C) 1999 American Institute of Physics. [S0034-6748(99)006 04-8].