研究目的
Developing an optical pressure measurement system with a wide continuous measurable range using an external cavity diode laser.
研究成果
The developed optical pressure measurement system can continuously measure a pressure range of 18 kPa with high precision, demonstrating potential for detailed evaluation of pressure gauge linearity and development of novel optical pressure sensors.
研究不足
The system's measurable range is limited by the frequency counter's capability, and temperature measurements may introduce errors due to differences between cavity surface and gas temperatures.
1：Experimental Design and Method Selection:
The study utilized a Fabry-Perot cavity with a Littrow external cavity diode laser (ECDL) as the light source to measure pressure by evaluating the refractive index of nitrogen gas. The Pound-Drever-Hall technique was used for frequency locking.
2：Sample Selection and Data Sources:
High-purity nitrogen gas with an impurity volume concentration of less than 0.5 vol. ppm was used. Pressure was measured simultaneously using a calibrated pressure gauge for comparison.
3：5 vol. ppm was used. Pressure was measured simultaneously using a calibrated pressure gauge for comparison.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included a Fabry-Perot cavity, ECDL (New Focus 6005 Vortex, Newport), electro-optic modulator, photodetector, frequency counter, and vacuum chamber.
4：Experimental Procedures and Operational Workflow:
The chamber was evacuated, filled with nitrogen gas to set pressures, and resonant frequencies were measured. The pressure was adjusted to set points, and measurements were repeated.
5：Data Analysis Methods:
Pressure was evaluated from measured frequencies and temperature using equations considering the refractive index and virial coefficients.
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