Design Of Ultrasonic Heat Meter Based On Phase-difference Integral Method

Currently, the ultrasonic heat meter is most widely used which is based on the timing chip such as gp21. However, this ultrasonic heat meter based on the time difference method can only measure the received waveform signal which is intercepted from the first few unstable waveforms, making the heat meter obviously deficient in accuracy and anti-jamming capability. Phase difference integral has vast superiority over time difference, because it measures the phase difference time intercepted directly from stable waveforms which makes the signal stable, the measurement time short and the signal amplitude nonfatal. This project aims to design a new heat meter which is based on phase difference method and can achieve high stability and high time resolution by increasing the integral numbers, shifting phase and changing the reference waveform duty ratio. The main content of this paper is as follows.In the first chapter, the research background and development status of heat meters were introduced, two kinds of flow measurement methods including time difference and phase difference integral were compared, and the project research purpose was come up with.In the second chapter, the scheme of the hardware circuit design was introduced, which includes the design of circuit of generating the phase difference pulse between two pulses based on a D flip-flop with reset function, the design of circuit of measuring the phase difference time based on charging and discharging the capacitor, the design of temperature measuring circuit based on a constant current source by Pt1000 resistance, and the design of other peripheral circuits.In the third chapter, a software program was demonstrated, which applied the interrupt mode to achieve low-power operation system, the TB7 timer with multiple interrupt vectors to output multiple timing control signals. The design of flow measurement, temperature measurement, M-bus communication, display, button and other program were introduced.In the fourth chapter, the performance of designed prototype was tested, and the comparison with the time difference hot meter was accomplished.Finally, a summary about the research work was come up with, and some expectations in the future were given which were combined with the technical development.