The Study Of Temperature Compensation On Ultrasonic Lfowmeter Transducer’s Operating Frequency

The small and medium caliber ultrasonic flowmeter is usually installed on metering skid inthe open air. However, in this environment, the operating ambient temperature changesfrequently. The ultrasonic transducer is the core component of the ultrasonic flowmeter, whichplays the function in energy conversion, the stability of transducer’s performance affects themeasurement precision of ultrasonic flowmeter. But the operating ambient temperatureinfluences the transfer characteristic of transducer, changing the optimum operating frequency oftransducer. When the pulse waveform from the sending transducer drives the receivingtransducer, the received waveform will produce differences, leading to a deviation of thezero-crossing position directly. The zero position is the important information which candetermine the transit time of ultrasonic flowmeter. Hence, the temperature compensation onultrasonic transducer’s operating frequency is essential to improve the measurement accuracy ofultrasonic flowmeter.According to the characteristic of ultrasonic transducer, the subject regards a dual-channelultrasonic flowmeter as the platform, using TMS320F2812DSP as the core chip, designing asystem of automatic temperature compensation on ultrasonic transducer’s operating frequency.The main tasks in this subject is embodied as follows:1) The background and significance of the research and the research status of ultrasonictransducer’s temperature compensation is investigated. The detection principle of the method oftime difference ultrasonic gas flowmeter is introduced, analyzing the effect of temperature on theflow detection and ultrasonic transducer.2) The optimum operating frequency of transducer is obtained at different temperature bythe experiment, using the mean value of two pairs of transducers’ optimum operating frequencyas the stimulated emission frequency; The value of the temperature, the voltage signal and thestimulated emission frequency are stored in memory, forming a linear list, acquiring the schemeof temperature compensation;3) The hardware circuit is designed which is related to temperature, including the circuit ofthe ultrasonic excitation signal, the ultrasonic receiving amplifier and the temperature detection.Besides, a modified method of transit time is used, completing the design of the whole system.4) Finally, the received signal waveform is collected, comparing the effect of temperaturecompensation for received waveform whether or not. And through the fluid flow of calibrationexperiment from prototype, compares the effect of temperature compensation for the velocity information whether or not. Meanwhile, the velocity information and the reference value iscompared, obtaining the measurement error of ultrasonic flowmeter.