A New Design For Ultrasonic Gas Flowmeter

Ultrasonic Gas Flowmeter is a new kind of flow instrument which works according to acoustics theory. This instrument is extensively used in natural gas, metallurgy, chemical industry. In this article, a new design for Ultrasonic Gas Flowmeter is expatiated in details. The instrument is designed as two individual parts: flow transducer and flow calculator. The microchip W78E58B of Winbond Co.is adopted as MCU. The design of ultrasonic transducer is based on piezoelectricity of the piezoelectric ceramic. Aiming at ultrasonic attenuation prodigiously in gas-flow, a new high voltage pulse cluster transmitting circuit is given combining with microchip and high frequency circuit design technology. It can improve transmitted and received waves obviously, then enhance the measuring precision and anti-jamming capability. Transferred to 4-20mA current by DAC, the result of flow rate is transmitted to the flow calculator because of the complex locale circumstance. In addition, the flow transducer has a RS-485 serial communication interfaces, the parameter can be set by computer. The flow calculator transfers the flow rate, pressure, temperature analogue signal to digital, then calculates the real time flow in standard condition and cumulates the flow. The real time flow, cumulate flow, history flow, pressure and temperature are displayed on the LCD.A keyboard is designed in this instrument, system parameter is set by the keyboard. The data is transmitted to computer by a isolated RS-485 interface.The article describes the design course of the Flowmeter in chapter: chapter 1 describes the theory of measuring flow by ultrasonic, the layout of the instrument is given in chapter 2, chapter 3 and 4 is about the design of flow transducer and flow calculator, chapter 5 and 6 introduces the serial communication protocol and the debugging of the instrument, the last chapter is the summarize.