Improved Acoustic Thermometry for Long-Distance Temperature Measurements

Area of Science:

• Metrology and Instrumentation
• Acoustics and Thermodynamics
• Industrial Manufacturing

Background:

• Accurate long-distance measurements (tens of meters) are critical in large-scale manufacturing, such as aerospace.
• Laser interferometers achieve high relative accuracy (10^-7) but depend on precise air temperature knowledge.
• Air temperature significantly impacts the speed of light, a key factor in laser interferometer accuracy.

Purpose of the Study:

• To develop and validate an acoustic thermometer for measuring air temperature along laser interferometer paths.
• To achieve high accuracy (0.1 °C) in temperature measurements over distances up to 11 meters.
• To assess the method's potential for measuring vertical temperature gradients affecting triangulation measurements.

Main Methods:

• Realization of an acoustic thermometer at INRIM based on measuring the speed of sound in air.
• Experimental setup description and performance evaluation.
• Comparison of acoustic thermometer readings with calibrated reference platinum resistance thermometers.

Main Results:

• The acoustic thermometer measures air temperature with an accuracy of 0.1 °C.
• Demonstrated capability for temperature measurement up to 11 meters.
• Validated performance against reference platinum resistance thermometers.

Conclusions:

• The acoustic thermometer provides accurate air temperature measurements essential for high-precision long-distance metrology.
• The method effectively addresses temperature-related errors in laser-based measurement systems.
• Potential application in mitigating errors caused by vertical temperature gradients in triangulation measurements.