CN-224202509-U - Capacitive electromagnetic flowmeter and signal processing circuit thereof

CN224202509UCN 224202509 UCN224202509 UCN 224202509UCN-224202509-U

Abstract

The application relates to a capacitive electromagnetic flowmeter and a signal processing circuit thereof, wherein the circuit comprises a measuring element, a signal processing module and a capacitance measuring module, the measuring element is used for measuring capacitance data and electromotive force signals of a component to be measured, the signal processing module is connected with the measuring element and is used for amplifying, filtering, signal extraction and signal conversion processing of the electromotive force signals to obtain digital signals and transmitting the digital signals to a CPU processing module, the capacitance measuring module is connected between the measuring element and the CPU processing module and is used for collecting the capacitance data and temperature data in the measuring element and transmitting the capacitance data and the temperature data to the CPU processing module. The circuit forms a digital integrated circuit through the measuring element, the signal processing module and the capacitance measuring module, and changes discrete analog measuring signals into digital measuring signals which are transmitted to the CPU processing module, so that the accuracy and the flexibility of measuring capacitance signals can be improved.

Inventors

WANG XIAPING
LIN HAO
SHA ZHENLONG

Assignees

上海一诺仪表有限公司

Dates

Publication Date: 20260505
Application Date: 20250604

Claims (10)

1. A signal processing circuit of a capacitive electromagnetic flowmeter, comprising: the measuring element is used for measuring capacitance data and electromotive force signals of the flow of the component to be measured; The signal processing module is connected with the measuring element and is used for amplifying, filtering, signal extraction and signal conversion processing of the electromotive force signal to obtain a digital signal; the capacitance measuring module is connected between the measuring element and the CPU processing module and is used for collecting capacitance data and temperature data in the measuring element and transmitting the capacitance data and the temperature data to the CPU processing module.
2. The signal processing circuit of the capacitive electromagnetic flowmeter according to claim 1, wherein the signal processing module comprises a first amplifying sub-module, a band-pass filtering sub-module, a synchronous demodulation sub-module, a second-order low-pass filtering sub-module, a second amplifying sub-module and an analog-to-digital conversion sub-module which are sequentially connected, an input end of the first amplifying sub-module is connected with an output end of the measuring element, and an output end of the analog-to-digital conversion sub-module is connected with an input end of the CPU processing module; The first amplifying submodule is used for amplifying the electromotive force signal and increasing the common mode rejection ratio of the signal to obtain a first processing signal; The band-pass filtering sub-module is used for carrying out filtering processing on the first processing signal to obtain a second processing signal of the square wave; the synchronous demodulation sub-module is used for extracting weak signals synchronous with the excitation magnetic field in the second processing signals to obtain third processing signals; The second-order low-pass filtering sub-module is used for filtering the third processing signal to obtain a fourth processing signal; The second amplifying submodule is used for carrying out differential amplification processing on the fourth processing signal to obtain a fifth processing signal; The analog-to-digital conversion sub-module is used for converting the fifth processing signal into a digital signal.
3. The signal processing circuit of a capacitive electromagnetic flowmeter of claim 2, wherein the first amplification submodule includes a first operational amplifier connected to the output of the measurement element and a second operational amplifier connected to the first operational amplifier, the output of the first operational amplifier being connected to the input of the band-pass filter submodule.
4. The signal processing circuit of a capacitive electromagnetic flowmeter according to claim 2, wherein the bandpass filtering submodule includes a filter, an input terminal of the filter is connected to the first amplifying submodule through a fifth resistor, and an output terminal of the filter is connected to an input terminal of the synchronous demodulation submodule.
5. The signal processing circuit of a capacitive electromagnetic flowmeter according to claim 2, wherein the synchronous demodulation submodule includes a demodulator, an input terminal of the demodulator is connected to the band-pass filter submodule, and an output of the demodulator is connected to the second-order low-pass filter submodule through a plurality of series resistors.
6. The signal processing circuit of a capacitive electromagnetic flowmeter according to claim 2, wherein the second-order low-pass filtering submodule includes a third operational amplifier, an anode input terminal of the third operational amplifier is connected to an output terminal of the synchronous demodulation submodule, an output terminal of the third operational amplifier is connected to the second amplification submodule, and an output terminal of the third operational amplifier is further connected to a cathode input terminal of the third operational amplifier through an eighth resistor.
7. The signal processing circuit of a capacitive electromagnetic flowmeter according to claim 2, wherein the second amplification submodule includes a differential amplifier connected to an output of the second-order low-pass filter submodule, and an output of the differential amplifier is connected to the analog-to-digital conversion submodule through a second-order filter circuit.
8. The signal processing circuit of a capacitive electromagnetic flowmeter of claim 7, wherein the second stage filter circuit comprises a forty-sixth resistor, a forty-seventh resistor, a fifty-first resistor, a fifty-third capacitor, a fifty-fourth capacitor, a fifty-fifth capacitor, and a fifty-sixth capacitor, a first end of the forty-sixth resistor being connected to a fifth connection terminal and a sixth connection terminal of the differential amplifier, respectively, a second end of the forty-sixth resistor being connected to a first end of the fifty-third resistor and a first end of the fifty-third capacitor, respectively, a second end of the fifty-fourth resistor being connected to a first end of the fifty-fourth capacitor and a second end of the fifty-fifth capacitor, respectively, a first end of the fifty-fifth capacitor being connected to a first connection terminal of the differential amplifier, a second end of the forty-seventh resistor being connected to a fourth end of the fifty-seventh resistor being connected to a first end of the fifty-fourth resistor and a second end of the fifty-fifth capacitor, respectively.
9. The signal processing circuit of a capacitive electromagnetic flowmeter of claim 2, wherein the analog-to-digital conversion sub-module comprises an analog-to-digital converter, an eleventh connection and a twelfth connection of the analog-to-digital converter being connected to the output of the second amplification sub-module, the analog-to-digital converter being further connected to the CPU processing module.
10. A capacitive electromagnetic flowmeter comprising a signal processing circuit of the capacitive electromagnetic flowmeter of any of claims 1-9.

Description

Capacitive electromagnetic flowmeter and signal processing circuit thereof Technical Field The application belongs to the technical field of capacitive electromagnetic flowmeters, and particularly relates to a capacitive electromagnetic flowmeter and a signal processing circuit thereof. Background The capacitive electromagnetic flowmeter is a meter for measuring fluid flow based on Faraday electromagnetic induction principle, and compared with a common electromagnetic flowmeter, the capacitive electromagnetic flowmeter has the working principle of combining electromagnetic induction and capacitive sensing technologies. The working principle of the capacitive electromagnetic flowmeter is that an alternating magnetic field is generated by applying a high-frequency 25HZ current source to an exciting coil, when a conductive fluid passes through the magnetic field, charged ions in the fluid are acted by Lorentz force, induced electromotive forces (E) are generated on two sides perpendicular to the magnetic field and the flowing direction, and the flow velocity of the fluid is calculated according to a formula (K is an instrument coefficient, B is magnetic induction intensity, D is pipeline diameter and V is fluid average flow velocity), so that the flow velocity is obtained. The signal processing circuit of the capacitive electromagnetic flowmeter is a core and a difficult point, wherein the stability and the high precision of the signal processing circuit directly determine the stability and the precision of the electromagnetic flowmeter. Compared with the traditional electromagnetic flowmeter, the metal electrode is used for directly contacting the fluid to detect the voltage, and the electrode covered by the ceramic insulating layer is used for capacitive coupling with the fluid. The induced electromotive force is transmitted to the external electrode through the fluid and the insulating layer, thereby forming a capacitive structure. The capacitance between the electrodes is modulated by the fluid potential change, thereby indirectly measuring the induced electromotive force. The induced electromotive force of the capacitive electromagnetic flowmeter is much smaller than that of the traditional electromagnetic flowmeter, and effective signals are required to be extracted through a high-sensitivity amplifier and a filtering technology. Compared with the traditional electromagnetic flowmeter, the electromagnetic flowmeter has the advantages of good corrosion resistance and dirt resistance, the insulating layer protects the electrode, is suitable for corrosive, high-viscosity or particle-containing fluid (such as chemical slurry, oily sewage and slurry solution), has low conductivity adaptability, can measure fluid with lower conductivity (such as pure water and certain organic solution) compared with the traditional electromagnetic flowmeter, has conductivity lower than 0.01uS/cm, really has a full-path structure, does not have a flow element, and reduces energy consumption. Disclosure of utility model An embodiment of the application provides a capacitive electromagnetic flowmeter and a signal processing circuit thereof, which are used for solving the problems of poor stability and low precision of the traditional capacitive electromagnetic flowmeter. In a first aspect, an embodiment of the present application provides a signal processing circuit of a capacitive electromagnetic flowmeter, including: the measuring element is used for measuring capacitance data and electromotive force signals of the flow of the component to be measured; The signal processing module is connected with the measuring element and is used for amplifying, filtering, signal extraction and signal conversion processing of the electromotive force signal to obtain a digital signal; the capacitance measuring module is connected between the measuring element and the CPU processing module and is used for collecting capacitance data and temperature data in the measuring element and transmitting the capacitance data and the temperature data to the CPU processing module. Optionally, the signal processing module includes a first amplifying sub-module, a band-pass filtering sub-module, a synchronous demodulation sub-module, a second-order low-pass filtering sub-module, a second amplifying sub-module and an analog-to-digital conversion sub-module which are sequentially connected, an input end of the first amplifying sub-module is connected with an output end of the measuring element, and an output end of the analog-to-digital conversion sub-module is connected with an input end of the CPU processing module; The first amplifying submodule is used for amplifying the electromotive force signal and increasing the common mode rejection ratio of the signal to obtain a first processing signal; The band-pass filtering sub-module is used for carrying out filtering processing on the first processing signal to obtain a second processing signal of the square wa