Research of acoustic methods for temperature measurement in liquids

: pp. 53-58
Lviv Polytechnic National University
Lviv Politecnic National University
Lviv Politechnik National University, Metrology and Informations-Measuring Technology Depatrment

In this work the subject of the research is the average temperature of liquids by using two acoustic methods: echo-pulse method and time-pulse method. For conducting the measurements the flow channel is used, through which water was passed, the temperature of which has changed and which must be measured. For the temperature measurements ultrasonic sensors are used, which are fixed on both sides of the current channel. The calculation of the special design of the mounting is made and the ultrasonic sensors are chosen. The size estimation of the glass coupling rod is made, based on the average temperature of the glass cylinder, thermal resistance, cylindrical glass square.The block diagram is presented for measuring the passage time of the ultrasonic signal in the measuring channel, according to which the transmitter and receiver are in direct contact with the pipe. For better contact ultrasonic gel was used. In addition, the oscilloscope to measure audio signals and device for generating acoustic pulses and their measurement using echo-pulse method are used. The results of studies using the echo pulse and the time-pulse methods are presented. The first measurement of the echo-pulse method was performed using the ultrasonic sensor on the pipe when the flow of water is active and the temperature of the water in the thermostat is fixed in the range from +10 C to 60 °C. The second dimension using this method is conducted when the flow of water is inactive in conditions of the same temperatures. The obtained results of measurements using the time-pulse method with an oscilloscope and an exemplary device when the temperature changes from 20 °C to 60 °C in increment of 10 are presented. The graphs of the dependencies obtained for all investigated temperatures are depicted. It is revealed that the current times of the sound pulses with increasing temperature are short. The chart is moved to the left. The signal on the oscilloscope screen in conditions of 60 °C is received. The first channel shows the audio signal acquiring with an exemplary device. The second channel shows the measuring signal. The next measurement is made with a glass cylinder, which is placed between the pipe and the ultrasonic sensor. The results of measurements using a glass cylinder in the temperature range from 20 °C to 60 °C are presented. The results of the carried out measurements show how the amplitude of the ultrasonic signals with a signal change is modified. Having this change it is possible to find the temperature which is needed to be determined. By using oscilloscope the dependence between amplitude and time of the ultrasonic signal is revealed. Studies have shown in which way the sound speed in water is changing with its internal temperature change.

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