[M-TT37] Brand-new scope of coupling geophysics being established by infrasound and associated waves

[MTT37-P06] Dynamic pressure measurement techniques around atmospheric pressure by laser interferometer

★Invited Papers

*Daichi Takahara¹, Hideaki Iizumi¹, Hiroaki Kajikawa¹ (1.National Institute of Advanced Industrial Science and Technology)

Keywords:Laser interferometer, Barometric pressure sensors, Dynamic characteristics, Evaluation and Calibration

We develop the evaluation equipment and technology for barometric pressure sensors. The dynamic characteristics such as amplitude and phase frequency characteristics of barometric pressure sensors are evaluated using this evaluation equipment as the reference for evaluating and calibrating barometric pressure sensors used in infrasound observation equipment. Target range for this evaluation is for pressure amplitudes from 10 Pa to 1000 Pa, and frequency from 1 mHz to 20 Hz. This technology aims to contribute to improving the reliability of infrasound observations. The evaluation system consists of a bellows (pressure generator) connected to a shaker, a measurement pressure chamber and a reference side pressure chamber, and a laser interferometer. From the Lorenz-Lorentz equation and the ideal gas law, changing the pressure of the measurement chamber also causes changes in the refractive index and optical path length. On the other hand, the pressure in the reference chamber is kept constant. The periodically varying differential pressure between the two chambers is measured by measuring difference of the optical path length between the two pressure chambers with the laser interferometer. The evaluation flow under consideration is that the value of the difference of optical path length measured by laser interferometer is statically valued by a pressure standard. And then, the value of the waveform of periodically changing optical path length difference measured is converted into a differential pressure using the result of the value assignment by the pressure standard. Finally, the evaluation is carried out by comparing the converted result with the measured waveform of the barometric pressure sensor to be evaluated, which is connected to the measurement chamber. In this report, the short-term (a few seconds) and long-term (about one hour) stability and repeatability of measurements by laser interferometry are compared with a high-precision differential pressure gauge to confirm the validity of differential pressure measurement by laser interferometry.