Design and realization of all digital closed-loop system of Coriolis mass flowmeter

The digital closed-loop system of Coriolis mass flowmeter (CMF), in which the field-programmable gate array (FPGA) and digital signal processing methods were used to realize stable and accurate closed-loop control, has good real time and high precision. The speed parallel component FPGA was adopted as core of calculation and control. The first in first out (FIFO) module was brought in the phase control, which change time difference by controlling the read and write request signals of FIFO, to realize the stable and accurate control of phase difference between vibrating and exciting signal. The amplitude was set rapidly and precisely by using nonlinear amplitude control manner with well adaption, which combined discontinuous and continuous amplitude control. It gets the good amplitude control to the vibrating signals, which was output stable by controlling. The measurement accuracy and stability were improved. The experimental results show that the dynamic response and stability of the system is improved. From the real-flow calibration tests, that CMF digital closed-loop is better than traditional analogue closed-loop in stability, dynamic response and repeatability. Furthermore, the measuring precision of CMF is enhanced.