Novel Nonrotational Piston Gauge with Weight Balance Mechanism for the Measurement of Small Differential Pressures

Abstract

Piston gauges are well-known standard instruments in the field of pressure metrology. But it is difficult to use them for small differential pressure measurements, because the pressure must be balanced against at least the weight of the piston, which generally corresponds to a pressure of several kilopascals. It is also difficult to reduce the pressure fluctuations caused by the rotation of the piston or the cylinder to lower than 0,1 Pa. A novel type of piston gauge has been developed in order to solve these problems and to measure small differential gas pressures in the range 1 Pa to 10 kPa with a sensitivity of about 5 mPa. This piston gauge uses two special features, of which one compensates for the weight of the piston and the other centralizes the piston in the cylinder without rotation. These mechanisms enable an electronic balance to measure the force produced on the piston by a small differential pressure.