Research On Ultrasonic Flow Measurement System Based On Transit Time Method

Fluid flow modulates propagation velocity of ultrasonic pulse, according to this, ultrasonic flow measurement technology which can measure flow is a new measurement technology. The ultrasonic flowmeter involved in the paper is liquid ultrasonic flowmeter installed outside the pipe. This type of flowmeters with characteristics of non-contact measurement, wide measuring range, has superiority in application on other plug-in ultrasonic flowmeters difficult to install and temporary flow measurement occasions. For the problems of this domestic ultrasonic flowmeter in the application, mainly some design has been made in hardware coding of ultrasonic pulse in the paper, so as to enhance the effective signal ratio and improve response speed of the flowmeter. In addition, some work has been done in temperature measurement and compensation in the paper. The measurement technology which can improve the temperature adaptability and precision was studied.On the basis of analyzing measurement principle and characteristics of the various ultrasonic flowmeter measurement methods, a set of ultrasonic flow measurement system based on improved transit time method was designed in the paper. The system uses a pair of ultrasonic transducers alternately transmitting and receiving ultrasonic signals. The core of processing is TI's DSP chip TMS320F2812, so as to ensure fast response. Hardware and software solutions have been given.The design work of secondary instrument of flowmeter includes selection of devices and chips, calculation of specific parameters and realization of functions, the design of the ultrasonic transmitted and received circuits, transducers switching control circuit, time measurement circuit , temperature measurement circuit , DSP core circuit and so on. The system uses the FSK signal to drive the ultrasonic emission of ultrasonic transducers and the receiving circuits demodulate the ultrasonic signals, so as to pinpoint the arrival time of ultrasonic signals. Propagation time of coded ultrasonic signals in the medium is measured by time measurement chip TDC-GP2 of German ACAM Company. The software consists of the control of PWM wave generation, accumulation of instantaneous flow, communication etc. Scheduling and management of programs are achieved by DSP / BIOS of TI.In addition, experiment has been made on this flowmeter, also measurement results have been calibrated and adjusted.At last, the work of this flow measurement system is summarized and the later work is put forward.