10:45 AM - 11:00 AM
[MTT38-06] Dynamic pressure measurement techniques around atmospheric pressure by laser interferometer -2-
★Invited Papers
Keywords:Laser interferometer, Barometric pressure sensors, Dynaimic characteristics, calibration
As a reference for the evaluation and calibration of barometric pressure sensors used in infrasound sensors, work is underway to develop a device that can evaluate the dynamic characteristics (amplitude and phase frequency characteristics) of barometric pressure sensors. The aim is to evaluate pressure amplitudes from 10 Pa to 1000 Pa and frequencies from 0.001 Hz to 20 Hz. The aim is that this technology will contribute to improving the reliability of infrasound observations.
The evaluation system consists of a bellows (pressure generator) conected to a shaker, a measurement and reference side pressure chambers and a laser interferometer. According to the Lorenz-Lorenz equation and the equation of state of an ideal gas, changing the pressure in the measurement side pressure chamber also causes changes in the refractive index and optical path length. On the other hand, the pressure in the reference pressure chamber is kept constant. The time-varying pressure is measured by measuring the periodically varying differential pressure between the two chambers by measurement the optical path length difference between the two pressure vessels with a laser interferometer. The dynamic characteristics are evaluated by comparing the measured waveforms of the interferometer with those of the atmospheric pressure sensor to be evaluated and calibrated. The evaluation process consists of statically valuing the optical path length difference values measured beforehand with a laser interferometer by means of a pressure standard. When a sinusoidal dynamic pressure is generated by the pressure generator, the value of the periodically changing optical path length difference waveform measured by the laser interferometer is converted into a differential pressure using the result obtained by the pressure standard. The evaluation is carried out by comparing the converted results with the measured waveform of the atmospheric pressure sensor to be evaluated, which is connected to the measurement side chamber.
In this report, the characteristics of this evaluation device under static pressure (pressure that does not change over time) are checked as static characteristics. Specifically, the short-term (a few seconds) and long-term (several hours) stability of the laser interferometer measurements, the linearity between the interferometer measurements and those of a high-precision differential pressure gauge, and the repeatability of the interferometer measurements are evaluated.
Dynamic pressure (time-varying pressure) is generated sinusoidally by the pressure generator described above, and the characteristics of this device are evaluated as dynamic characteristics. Specifically, the effects of the temperature change that occurs during the sinusoidal dynamic pressure generation on the measured values of the laser interferometer will be evaluated, and the frequency characteristics (amplitude and phase) of the measured values of the laser interferometer will be evaluated by comparing them with the amplitude of the bellows of the pressure generator.
The evaluation system consists of a bellows (pressure generator) conected to a shaker, a measurement and reference side pressure chambers and a laser interferometer. According to the Lorenz-Lorenz equation and the equation of state of an ideal gas, changing the pressure in the measurement side pressure chamber also causes changes in the refractive index and optical path length. On the other hand, the pressure in the reference pressure chamber is kept constant. The time-varying pressure is measured by measuring the periodically varying differential pressure between the two chambers by measurement the optical path length difference between the two pressure vessels with a laser interferometer. The dynamic characteristics are evaluated by comparing the measured waveforms of the interferometer with those of the atmospheric pressure sensor to be evaluated and calibrated. The evaluation process consists of statically valuing the optical path length difference values measured beforehand with a laser interferometer by means of a pressure standard. When a sinusoidal dynamic pressure is generated by the pressure generator, the value of the periodically changing optical path length difference waveform measured by the laser interferometer is converted into a differential pressure using the result obtained by the pressure standard. The evaluation is carried out by comparing the converted results with the measured waveform of the atmospheric pressure sensor to be evaluated, which is connected to the measurement side chamber.
In this report, the characteristics of this evaluation device under static pressure (pressure that does not change over time) are checked as static characteristics. Specifically, the short-term (a few seconds) and long-term (several hours) stability of the laser interferometer measurements, the linearity between the interferometer measurements and those of a high-precision differential pressure gauge, and the repeatability of the interferometer measurements are evaluated.
Dynamic pressure (time-varying pressure) is generated sinusoidally by the pressure generator described above, and the characteristics of this device are evaluated as dynamic characteristics. Specifically, the effects of the temperature change that occurs during the sinusoidal dynamic pressure generation on the measured values of the laser interferometer will be evaluated, and the frequency characteristics (amplitude and phase) of the measured values of the laser interferometer will be evaluated by comparing them with the amplitude of the bellows of the pressure generator.