The Study Of Coriolis Mass Flowmeter Based On Dsp

With the features of high precision and wide application, Coriolis Mass Flo-wmeter can measure the quality of fluid directly and has been applied in indust-ry. However, with the development of technology, the traditional measuring meth-od has some shortages. It has failed to meet the demands of people. So, we try to utilise the digital signal processing method to deal with the signal generated from CMF.In this thesis, DSP chip is used as the CPU of digital signal processing. It combines with Fast Fourier Transform method, and develops a kind of digital CMF. The traditional analog methods are easy to be disturbed by noises and the measurement accuracy is not high. The application of digital signal processing methods solve the problems mentioned above, and improve the execution speed.Firstly, this thesis introduces the structure, working principle and development of CMF, illustrates the main problems to be solved. Furthermore, the digital signal processing methods are put forward, the hardware circuit is constructed, and software design of the system is introduced concretely. Conlusions and discussions are give finally.In this thesis, the hardware system of the flowmeter consists of the drivier module and signal acquisition and processing modual,the signal was divided into two signals, frequence,phase and amplitude,and multiplying the two signals to obtain the required signal through the multiplier,then driving the vibration of the flow tube; Signal acquisition and processing module using TMS320F28335, DSP chip as the CPU, This module consists of a signal amplifying and filtering circuit, AD converter circuit, digital signal processing circuit, RS232circuit, LCD,4～20mA current and pulse output,completing of the acquisition and processing of sensor signals, the Results are showed by the LCD and are delivered to the control room through the4to20mA current and pulse output,and the system is good proved by the test.The modular method is used to solve the software system, and it can be divided into system monitoring module, initial module, interrupt module, AD conversion module, phase difference computation module, PC communication module, and LCD module, etc. It is convenient that each module could be called by the main module seperately. It causes the conveniences of debugging and error check in programming. The Radix-2Decimation-In-Time Fast Fourier Transform(FFT) method is applied to overcome the complexity of Discrete Fourier Transform method. It increases the rate of calculation, and achieves the accurate calculation of the phase difference.