All-digital closed-loop system of Coriolis mass flowmeter

Abstract

The invention provides an all-digital closed-loop system of a Coriolis mass flowmeter (CMF). A hardware circuit is based on digital components to achieve the stable closed-loop control of the CMF, particularly, the digital signal processing circuit is mainly based on a field programmable gate array (FPGA), and a digital signal processing method is used in the FPGA to achieve the digital closed-loop control algorithm for the CMF and track the frequency on a real-time basis; by using the non-linear amplitude control method and introducing FIFO (first in, first out) components to the phase control, stable and accurate control can be achieved on the amplitude and phase; by better tracking the changes in the vibration of the measuring tube of the CMF to obtain vibration pickup signals reflecting the information of fluid more accurately and further output the vibration pickup signals at a stable amplitude, the invention is favorable for resolving a secondary meter, further improving the accuracy and stability in the measurement of the CMF and ensuring that the resource consumption and operation load are lower; and the invention further solves the problem of two-phase flow, particularly, when the CMF undergoes the problem of two-phase flow, the sinusoidal signal at the controllable amplitude and at the same frequency as the natural frequency of the measuring tubes of the CMF can be actively outputted to force the measuring tubes of the CMF to continue vibrating, thus ensuring the non-stop vibration and non-interrupted measurement when the CMF undergoes the problem of two-phase flow and enabling the CMF to carry out the flow measurement when undergoing the problem of the two-phase flow.

Description

technical field [0001] The invention relates to an all-digital closed-loop system of a Coriolis mass flowmeter, which uses digital devices and digital signal processing methods to perform stable and precise closed-loop control on CMF. Background technique [0002] A Coriolis mass flowmeter (Coriolis mass flowmeter, hereinafter referred to as CMF) can directly measure fluid mass flow with high precision. Figure 5 Shown is a typical U-tube CMF system structure diagram. The CMF system consists of a sensor sensitive unit and a secondary instrument, where the sensitive unit includes an exciter, a measuring tube and a vibration pickup, and the secondary instrument includes a closed-loop control unit and a flow calculation unit. The closed-loop control unit provides an excitation signal to the exciter, so that the measuring tube generates a corresponding sinusoidal vibration. When the fluid flows through the measuring tube, the measuring tube is subjected to Coriolis force and twi...

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Problems solved by technology

In addition, the invention solves the problem of CMF two-phase flow, avoids the vibra

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