An Ultra-High Accuracy Temperature Measurement Method using Acoustic Waveguide

Abstract

This article presents a very precise approach to measuring temperature in a wide temperature range using ultrasonic waves. A lead zirconate titanate (PZT) piezoelectric transducer is used to excite ultrasonic shear waves and a solid stainless steel waveguide is selected to confine the ultrasonic wave propagation path. The shape and dimensions of the waveguide were theoretically optimized and numerically simulated to propagate robust, non-dispersive wave, and protect the fragile PZT from high temperature. Ultrasonic wave velocity is highly temperature dependent. The travelling time of wavepacket along the waveguide exhibits a corresponding relationship with the average temperature at measurement zone of the waveguide. Detailed experimental verification and validation processes, together with a calibration stage, were conducted up to 200°C, a temperature that is on par with the operating range of the resistance temperature detector (RTD) used for calibration. Stability test demonstrated that our technique attains a high accuracy (i.e. ±0.1%) which is comparable with the highest precision standard of commercial RTDs along the calibrated temperature range. Temperature tracking test was operated to unfold the temperature measuring and tracking capability of the ultrasonic wave technique in different liquids. This ultrasonic technique is robust and customizable, hence providing a promising alternative for accurate and stable contact thermometry.