Simple single transducer ultrasonic thermometer using electrostatic actuator

摘要

This article presents an experimental setup for the ultrasonic temperature measurement with a single acoustic transducer. The ultrasonic thermometer uses the simple impulse-echo method to determine the time of flight of short 75 kHz acoustic bursts travelling through a waveguide from which the velocity of sound and subsequently the temperature (of the environment surrounding the waveguide) is computed. The waveguide consists of 500 mm long stainless steel tube with an inner diameter of 22 mm, connected in series with a tube of the reduced diameter (10 mm, 171 mm long). The difference in cross sections of respective parts allows to determine sound velocity only in the segment of the thermometer which is fully immersed into the measured medium. The whole system is controlled by the NI LabVIEW application which uses the NI PXI system for both generating the signal for the electrostatic actuator and measuring the signal from the receiver part of the circuit. Implementation of the electrostatic actuator allows to use one acoustic transducer without the need of complex supporting electronics or time synchronisation between signals. All the signals representing the initial acoustic pulse and echoes from the waveguide are present in a single channel record. The temperature estimation is computed from basic signal parameters. The principle of the thermometer prototype operation and first calibration results in the temperature range of (-20 to 90) degrees C are shown. Results of calibration and subsequent interpolation applied on measured data show current limits of the thermometer. (C) 2019 Elsevier Ltd. All rights reserved.