Research On Improving Performance Of Ultrasonic Flowmeter

Ultrasonic flow measurement technology, which developed rapidly in recent several ten years, is a new-style flow measurement technology. It uses the liquid velocity information carried by the ultrasonic when it is propagating in the liquid to measure the flow of liquid. The main merits of the flowmeter is non-contact, high accuracy, wide measurement scope, convenience of installation and maintenance, especially acceptable for measurement of temporary flow, large flow, and flow in dangerous environment. In recent ten years, on the basis of development of high-speed digital signal processor and microprocessor, on the basis of research for new-style probe material and technology, on the basis of research for acoustic channel configuration and flow mechanic, the ultrasonic flow measurement technology has obtained a great advancement, showing its strong technical advantage and becoming animportant flow measurement technology. The paper introduces basic principle and realizing method of the ultrasonic flow measurement technology. On basis of absorbing and refering to the domestic and foreign advanced ultrasonic flow measurement technology, the intact system hardware is designed and the design idea of the system software is given. Considering the development state and the existent demerits of the domestic ultrasonic flow measurement technology presently, the following several problems are mainly discussed and solved:1. With regard to the problem of stability and reliability. First, delay window is used to reduce influence of pulse disturbance and signal amplitude to measurement result. Second, according to the feature that width of receiving signal is wider than disturbing signal, width differentiation circuit is utilized to distinguish receiving signal and disturbing signal. Third, most of digital circuits are integrated into ispLSI(in system programmable large scale integrated chip ) 1032 so as to simplify design and to develop thestability and reliability of the system.2. With regard to the problem of improving accuracy and measurement scope of the system. First, better matching emitting and receiving circuits is designed to improve work efficiency. Second, logarithmic amplifier is used to enhance amplifier dynamic scope. Third, double threshold method is adopted to eliminate the error caused by different amplitude of receiving signal. Forth, with regard to measurement for transmitting time, PLL technology is used to elevate time measurement precision. Fifth, flow revision coefficient is studied and analyzed, and calculation formulae of the flow revision coefficient are given under different state.