All-digital closed-loop system of Coriolis mass flowmeter
A mass flowmeter, Coriolis technology, applied in the field of full digital closed-loop system of Coriolis mass flowmeter, to achieve the effect of avoiding vibration stop and improving measurement accuracy
Active Publication Date: 2011-11-30
BEIHANG UNIV
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In addition, the invention solves the problem of CMF two-phase flow, avoids the vibration stop of the measuring tube, and maintains the normal measurement of the flow rate
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[0030] Such as figure 1 As shown, the present invention includes an analog signal preprocessing circuit 1, an analog-to-digital signal conversion circuit 2 ( figure 2 A / D module for short), digital signal processing circuit 3, digital-to-analog signal conversion circuit 9 ( figure 2 It is composed of D / A module for short) and analog signal amplifying circuit 10. First, the analog signal preprocessing circuit 1 preprocesses the analog signal output by the CMF vibrator, uses the high input impedance operational amplifier OPA2336 to amplify the CMF output signal by 2.5 times, and then uses RC to form a low-pass filter, and cooperates with the subsequent A / The D module samples to achieve the purpose of anti-aliasing filtering.
[0031] The analog-to-digital signal conversion circuit 2 adopts a 20-bit analog-to-digital conversion chip to sample the analog signal output by the analog signal preprocessing circuit 1 according to the set sampling rate;
[0032] The digital signa...
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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...
Claims
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IPC IPC(8): G01F1/84
Inventor 郑德智王帅樊尚春田婧
Owner BEIHANG UNIV