Research On The Coriolis Mass-flow Meter With High Sensitive

Coriolis Mass Flow meters were invented in the 1970's, when the modern industry was developing fast and the custom mass-flow measurement was unable to fulfill the requirement. Its invention has greatly changed the situation of the mass-flow measurement. But there are still some problems to be solved wanting studying, such as avoiding the influence from the noise, density of flower liquid and temperature and raising the precision. Coriolis Mass Flow meters with high precision haven't been invented for long, which makes it impossible to measure mass flow of gases, even the mass flow of liquid with more than 5% of gases in it. Thus to improve the precision has become a crucial issue in this field. Aiming at the improvement of the precision of Coriolis Mass Flow meters, this thesis develops a new tube-shaped device and measures the phase difference with a digital signal-based measurement. Analog/digital conversion is adopted to transfer measured signals to data and periods are figured out. The DFT technique is used to process the signals from the sensors of Coriolis mass flow meter, and to calculate the frequency and the phrase differences, from which the data obtained are used for analysis for each type of tube-shaped design. In the same time, a platform for test is established and a practical frequency-tracking method with high precision is brought forward to realize the integral period sampling of signals and to ensure the precision of digital signal processing. A real-time signal processing system based on DSP processor including hard ware and software is produced. The hardware of it the system is made up with signal sampling channels, analog/digital converter, CPLD chip logic controller, LCD display circuit, keyboard input circuit, temperature detector and output circuit. The software of it includes the interrupt service module, initialization module, phase difference measurement module, frequency tracking module, keyboard monitor module and display module. The drive circuit and the processing program in PC are also produced in this thesis. According to the results of simulation and experiment, the technique and the system in this thesis are feasible and effective, the system has laid a good foundation for later-on deep research of DFT technique application for the Coriolis mass-flow meter.