A Heterodyne Laser Interferometric Oil Manometer

This paper describes the principle and performance of a novel manometer developed for the measurement of pressures in the range of up 1 kPa. A heterodyne interferometer using a Zeeman stabilized He-Ne laser was used to detect the displacement of oil surfaces which reflect the laser beam directly. A system of double U-tube and double interferometer was used to compensate errors caused by thermal and vibrational disturbances. The total uncertainty of the measured pressure P is estimated to be ± (2,1 + 0,032 P /Pa)mPa for gauge-mode pressures. The operation of the manometer has been confirmed by the calibration of three capacitance diaphragm gauges at gauge-mode pressures of up to 876 Pa.