Research On Time-difference-type Ultrasonic Flowmeter

Ultrasonic flowmeter has been widely used in waterworks, oil industry, chemical industry and electric power plant in virtue of its many advantages, such as non-contact, wide measurement scope, convenience of installation, especially acceptable for measurement of large flow and flow in dangerous environment. However, the ultrasonic flowmeter develops just some ten years, and has some disadvantages, thus it is necessary to make modification and advance.After deep market investigation and many references about the ultrasonic flowmeter, we choose time-difference-type ultrasonic flowmeter for our study objects. The article makes deep theoretical research on the problem of improving accuracy, stability and reliability. In addition, it supplies the designs of circuits. Generally, there are five parts as the following:1. Expouded the principles of some ultrasonic flowmeter, especially about the time-difference-type ultrasonic flowmeter; researched the transducer the propagation character of ultrasonic in fluid. Then the ultrasonic flowmeter was corrected according to the theory of hydromechanics and physics, and calculation formulae of the flow revision coefficient are given under different state.2. On account of the problem that the accuracy of traditional ultrasonic flowmeter is easily influenced by temperature, adopt an improved algorithm which can avoid the influence on accuracy by temperature variation to some extent; introduce several means about precise measurement on propagating time, meanwhile, discuss the theory and application of a brand new measurement method--the multi-beams method deeply.3. Taking the study into consideration, analyze and design the hardware circuit of flowmeter in detail, discuss some technical matters such as chip selection and parameters calculation, design a better matching emitting and receiving circuits, use routine filter circuit and automatic gain control circuit to adjust signal; furthermore, with the help of double MCU, the resist ability of system to disturbing is improved strongly. In software, the soft flow chart of system and the design idea of the system are given.4. Considering the environment the ultrasonic flowmeter worked, the anti-jamming of the flowmeter system are discussed, and the corresponding methods of soft and hardware are adopted to minish or remove the interfere.