An acoustic thermometer for air refractive index estimation in long distance interferometric measurements
| Autor: | Massimo Zucco, Marco Pisani, Milena Astrua |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Physics
Microphone business.industry 020208 electrical & electronic engineering General Engineering 02 engineering and technology Acoustic wave 01 natural sciences Signal 010309 optics Amplitude modulation Interferometry Optical path Optics Thermometer Speed of sound 0103 physical sciences 0202 electrical engineering electronic engineering information engineering business |
| Zdroj: | Metrologia. 55:67-74 |
| ISSN: | 1681-7575 0026-1394 |
| Popis: | We present a method to measure the temperature along the path of an optical interferometer based on the propagation of acoustic waves. It exploits the high sensitivity of the speed of sound to air temperature. In particular, it takes advantage of a technique where the generation of acoustic waves is synchronous with the amplitude modulation of a laser source. A photodetector converts the laser light into an electronic signal used as a reference, while the incoming acoustic waves are focused on a microphone and generate the measuring signal. Under this condition, the phase difference between the two signals substantially depends on the temperature of the air volume interposed between the sources and the receivers. A comparison with traditional temperature sensors highlighted the limit of the latter in the case of fast temperature variations and the advantage of a measurement integrated along the optical path instead of a sampling measurement. The capability of the acoustic method to compensate for the interferometric distance measurements due to air temperature variations has been demonstrated to the level of 0.1 °C corresponding to 10−7 on the refractive index of air. We applied the method indoor for distances up to 27 m, outdoor at 78 m and finally tested the acoustic thermometer over a distance of 182 m. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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