Abstract
A laser interferometric oil manometer is developed for use as a national primary standard in the pressure range up to 1000Pa. The 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 phenyl ether diffusion-pump oil (NEOVAC-SY, Matsumura Oil Co. Ltd.) with low vapor pressure, suitable density and viscosity is employed as the manometer fluid. The density of the manometer fluid was measured using pyknometers and its value at 32°C was 916.329kg/m3 with an uncertainty of 27ppm. The total uncertainty of the new manometer is evaluated to be (27ppm+0.5mPa) for gauge-mode pressure.
