The Design Of High Precision And Low Power Transit-time Ultrasonic Flowmeter

With the rapid development of modern industries, flow measurement is indispensable now. Due to its' Ultrasonic flowmeter can measure without touching measured substance or intermitting pipe and its' measurement accuracy can hardly be influenced by the temperature of medium, pressure and other parameter. So it has got widely used.Using the measure theory of transit-time method and an anti-jamming incepted waveform treatment technique, the system has improved its measure effect. A time-to-digital converter chip TDC-GP2 which can measure time intervals with very high precision and control pulse transmit is used. A low power loss microcontroller MSP430F155 is used as the core of system to control and calculate. The CPLD ispMACH4064 complete the function of extraction pulse from incepted waveform and automatic gain control.Using CPLD to deal with the incepted waveform signal can improve the precision of extraction pulse, eliminate interference effectively, it established the foundation of high precise time intervals measurement.GP2 use internal propagation delays of signals through gates to measure propagation time of system .It has higher precision than traditional high-speed digital counter method, and can work at 1 MHz to avoid complicated high frequency circuit interference and whatsoever.In the embedded worktable-IAR Embedded Workbench, C language is used to complete controlling and data traffic, which achieving the necessary measurement flow of industry automatic instruments. Using C language for programming can improve work efficiency greatly, improve the reliability readability and replanted of the program, and it is convenient to continue perfecting and extending the design.The transit-time ultrasonic flowmeter applied in the thesis has adopted time-measurement chip to measure transit-time and has applied CPLD to accomplish the hardware anti-jamming circuit of extraction in incepted waveform to ensure the high system measurement precision and has used the low power loss and fast computing ability of microcontroller to accomplish the stability of system controlling and manage. The design improves the measurement effect of ultrasonic flowmeter exactly, which gets the anticipatory aim.After correct fixing, checkout, adjusting and setting locale parameter accurately, the measurement precision of system can be about 1%.