ヘテロダイン干渉法による油マノメータの液位差の精密測定

抄録

This paper describes the principle and performance of a novel interferometer developed for the measurement of differential height of an oil manometer for use in the range up to 1 kPa. The heterodyne interferometry using Zeeman stabilized He-Ne laser was applied to detect the displacement of oil surfaces which reflect laser beam directly. A system of double U-tube and double interferometer was introduced and developed in order to compensate errors caused by thermal and mechanical changes. The performance of the system was estimated from the experiments in which silicon oil of 100 mm²/s kinematic viscosity was selected as a manometer fluid. The short term and long term stabilities of zero-point are evaluated as standard deviations of 0.001 μm in 5 seconds and 0.01 μm in 3 days, respectively. The hysteresis of zero-point is 0.01 μm after 1 000 Pa pressurizing, during which the oil surfaces can be moved with a speed of up to 25 mm/min. The overall uncertainty of this system is estimated to be 0.026 μm.