Design Of Time Difference Ultrasonic Flowmeter Based On ARM

The accuracy of flow measurement has become increasingly demanding with the rapid development of science and technology. Therefore, the high-precision measuring is very important for the flow liquid. The ultrasonic flowmeter with the characters such as portable, non-contact measurement, high-precision, intelligent has been widely used in the flow measurement.In this paper, the development situation and characteristics of the domestic and international ultrasonic flowmeter are described in detail and the characteristics of the flow measurement and distribution of pipe-flow are introduced. The design method of the time-difference ultrasonic flowmeter based on ARM is proposed which takes the measurement theory of time-difference as the basis. In the hardware circuit, the microprocessor chip S3C2440A with high cost performance and low power loss is selected as the core of control system which is responsible for the control of signal, algorithm processing, data communications, and other functions. Using the chip CPLD ISP1253 in system programmable completes the ultrasonic pulse of sending and receiving, waveform signal picking and window signal control. While the time-to-digital converter chip TDC-GP2 achieves high precision measurement of time difference. Signal amplification circuit, filter circuit and auto-gain circuit are designed that enhances the anti-interference ability in order to improve the flowmeter measurement accuracy in the hardware.In software design, the paper describes the transplanting methods and steps of the system structure to put up an embedded Linux system development environment for the software design of the time-difference ultrasonic flowmeter. According to the microprocessor with the characteristics such as high processing speed and supporting embedded operating system, a frequency-domain filtering of the data processing algorithm is proposed in order to improve the accuracy, stability and linearity of the flowmeter. In order to input the parameters of pipeline and enhance data display in time man-machine interface is designed using the develop tool QT. In addition, the software design and development of data communication part make data collected in time transmit to PC for analysis and preservation in order to improve the ability of detection and intelligent of the flowmeter.Field test shows that the design method improves the measuring accuracy and meets the requirement of the high measuring accuracy and the flow measurement has good prospects.