Temperature influence on the ultrasonic signal acquisition path

Abstract

It is important to estimate the group delay time in systems where signal delay is used to extract the measured parameter. In this article the ultrasonic flow measurement system is analyzed. Measurement is carried out using ultrasonic signal, which travels along and against the measured flow. The pulsed delay time measurement technique is used. The system is synchronized by a quartz oscillator. A digital pulse former is used to excite the high voltage generator which in turn delivers the signal to ultrasonic transducer. The transducer is sending the acoustical pulse into liquid in measurement channel. This pulse is received by the transducer at the opposite channel end and converted into electrical signal. This is amplified, filtered and delivered into analog to digit converter. The goal of this investigation was to estimate the temperature influence on the group delay time of the system discussed above. Electrical models have been developed in PSPICE, simulation carried out. Theoretical analytical expressions of the delay time influence on a flow speed estimation are presented.
Temperature influence of individual units was investigated experimentally. Experimental results are presented in numerical and graphical form. It has been concluded that the high voltage generator output stage has the highest temperature sensitivity on delay time among electronics units. But according to the analytical expressions, this influence can be compensated. Then the largest electronics contribution on the group delay time is due to the analog filters present in the signal path.