Towards the realization of an optical pressure standard

A novel pressure standard based on optical interferometry has been realized. The paper presents a preliminary achievement of the system, in which the standard pressure between 1 kPa and 120 kPa is obtained through the measurement of the refractive index of a gas. The response of the optical system has been initially evaluated measuring its sensitivity for nitrogen and air, in terms of the ratio between a pressure variation and the number of detected interferometric fringes. Afterwards, the interferometer has been geometrical characterized in order to perform an absolute measurement of the refractive index of the gas, allowing an optical measurement of the gas pressure. The following step has been to compare the results of a series of measurements obtained with the optical system with a reference pressure standard at 120 kPa. Finally, the standard has been compared with two capacitance diaphragm gauges in the range between 1 kPa and 120 kPa. The device has a relative standard uncertainty equal to 170 ppm at atmospheric pressure.