Electromagnetic Sensing Device and Its Signal Conditioning Method

Abstract

The present application relates to an electromagnetic sensing device and a signal conditioning method thereof. The device includes: a control module, an excitation signal adjustment module, an induced signal conditioning module, a human-machine interaction module, and a primary excitation coil and a secondary induction coil arranged near the liquid level to be detected; wherein, the control module includes a first port connected to the human-machine interaction module, a second port connected to the excitation signal adjustment module, and a third port connected to the induced signal conditioning module; the excitation signal adjustment module is connected to the primary excitation coil, and the excitation signal adjustment module is configured to adjust the frequency and amplitude of the excitation signal according to the parameter values output from the second port, and output the adjusted excitation signal to the primary excitation coil; the induced signal conditioning module is connected to the secondary induction coil, and the induced signal conditioning module is configured to condition the induced signal according to the parameter values output from the third port to obtain a liquid level signal for characterizing the liquid level to be detected, so as to make the detection result of the liquid level to be detected more accurate.

Description

Technical Field

[0001] The present application relates to the technical field of liquid level detection, and particularly to an electromagnetic sensing device and a signal conditioning method thereof. Background Art

[0002] During the casting process of high-quality continuous casting billets, the liquid level height of the molten steel mold is a very important control index. If the liquid level fluctuates by more than ±3 mm, it will not only seriously affect the quality of the billets and downgrade their quality, but may also cause forced shutdowns and even safety accidents such as molten steel leakage, resulting in serious economic losses and personal risks. Therefore, it is crucial to improve the accuracy of the detection results of the liquid level height of the molten steel mold.

[0003] In the prior art, electromagnetic sensors are usually used to detect the liquid level height. However, since the excitation signal frequency of the primary coil in the existing electromagnetic sensors is fixed, and the center frequency point of the band-pass filtering module for filtering the induced signal of the secondary coil is also fixed, it is difficult to avoid electromagnetic interference generated by various on-site devices (such as electromagnetic stirring, electromagnetic braking, etc.) during actual application, resulting in low accuracy of the detection results of the liquid level height. Summary of the Invention

[0004] The present application provides an electromagnetic sensing device and a signal conditioning method thereof to solve the problem of low accuracy of the detection results of the liquid level height in the existing electromagnetic sensors.

[0005] In a first aspect, an embodiment of the present application provides an electromagnetic sensing device, which includes: a control module, an excitation signal adjustment module, an induced signal conditioning module, a human-machine interaction module, and a primary excitation coil and a secondary induction coil disposed near the liquid level to be detected;

[0006] Among them, the control module includes a first port connected to the human-machine interaction module, a second port connected to the excitation signal adjustment module, and a third port connected to the induced signal conditioning module;

[0007] The excitation signal adjustment module is connected to the primary excitation coil. The excitation signal adjustment module is used to adjust the frequency and amplitude of the excitation signal according to the parameter value output from the second port, and output the adjusted excitation signal to the primary excitation coil. The primary excitation coil is used to generate an alternating magnetic field according to the adjusted excitation signal;

[0008] The induced signal conditioning module is connected to the secondary induction coil. The secondary induction coil is used to generate an induced signal according to the alternating magnetic field. The induced signal conditioning module is used to condition the induced signal according to the parameter value output from the third port to obtain a liquid level signal for characterizing the liquid level to be detected;

[0009] The parameter values output from the second port and the parameter values output from the third port are adjusted based on the parameter adjustment instruction received by the first port.

[0010] Optionally, a control unit, a first digital-to-analog conversion circuit, and a first pulse modulation circuit are encapsulated in the control module; the excitation signal adjustment module includes a signal modulation circuit and a power amplifier circuit;

[0011] Wherein, the input end of the first digital-to-analog conversion circuit and the input end of the first pulse modulation circuit are both connected to the control unit, the output end of the first digital-to-analog conversion circuit and the output end of the first pulse modulation circuit both serve as the second port and are connected to the input end of the signal modulation circuit, the output end of the signal modulation circuit is connected to the input end of the power amplifier circuit, and the output end of the power amplifier circuit is respectively connected to the feedback end of the signal modulation circuit and the primary excitation coil.

[0012] Optionally, a second digital-to-analog conversion circuit, a second pulse modulation circuit, a third pulse modulation circuit, a first analog-to-digital conversion circuit, and a second analog-to-digital conversion circuit are further encapsulated in the control module; the induction signal conditioning module includes a first signal amplifier circuit, a first operational amplifier circuit, a first band-pass filter circuit, a first switched-phase-sensitive demodulation circuit, a second switched-phase-sensitive demodulation circuit, a first low-pass filter circuit, a second low-pass filter circuit, a second operational amplifier circuit, and a third operational amplifier circuit;

[0013] Wherein, the input end of the second digital-to-analog conversion circuit, the input end of the second pulse modulation circuit, the input end of the third pulse modulation circuit, the output end of the first analog-to-digital conversion circuit, and the output end of the second analog-to-digital conversion circuit are all connected to the control unit, and the output end of the second digital-to-analog conversion circuit, the output end of the second pulse modulation circuit, and the output end of the third pulse modulation circuit all serve as the third port;

[0014] The output end of the second digital-to-analog conversion circuit is connected to the input end of the first operational amplifier circuit, and the output end of the first operational amplifier circuit is connected to the control end of the first band-pass filter circuit; the output end of the second pulse modulation circuit is connected to the control end of the first switched-phase-sensitive demodulation circuit, and the output end of the third pulse modulation circuit is connected to the control end of the second switched-phase-sensitive demodulation circuit;

[0015] The secondary induction coil is connected to the input end of the first signal amplification circuit, the output end of the first signal amplification circuit is connected to the input end of the first band-pass filter circuit, the output end of the first band-pass filter circuit is respectively connected to the input ends of the first switched phase-sensitive detection circuit and the second switched phase-sensitive detection circuit, the output end of the first switched phase-sensitive detection circuit is connected to the input end of the first low-pass filter circuit, the output end of the first low-pass filter circuit is connected to the input end of the second operational amplifier circuit, and the output end of the second operational amplifier circuit is connected to the input end of the first analog-to-digital conversion circuit; the output end of the second switched phase-sensitive detection circuit is connected to the input end of the second low-pass filter circuit, the output end of the second low-pass filter circuit is connected to the input end of the third operational amplifier circuit, and the output end of the third operational amplifier circuit is connected to the input end of the second analog-to-digital conversion circuit.

[0016] Optionally, the center frequency of the first band-pass filter circuit is adjusted based on the voltage amplitude output by the second digital-to-analog conversion circuit, and the center frequency of the first band-pass filter circuit is equal to the frequencies of the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit.

[0017] Optionally, the device further includes a compensation induction coil disposed near the secondary induction coil; a third digital-to-analog conversion circuit, a fourth pulse modulation circuit, a fifth pulse modulation circuit, a third analog-to-digital conversion circuit, and a fourth analog-to-digital conversion circuit are further encapsulated in the control module; the induction signal conditioning module further includes a second signal amplification circuit, a fourth operational amplifier circuit, a second band-pass filter circuit, a third switched phase-sensitive detection circuit, a fourth switched phase-sensitive detection circuit, a third low-pass filter circuit, a fourth low-pass filter circuit, a fifth operational amplifier circuit, and a sixth operational amplifier circuit;

[0018] Among them, the input ends of the third digital-to-analog conversion circuit, the fourth pulse modulation circuit, the fifth pulse modulation circuit, the output end of the third analog-to-digital conversion circuit, and the output end of the fourth analog-to-digital conversion circuit are all connected to the control unit, and the output ends of the third digital-to-analog conversion circuit, the fourth pulse modulation circuit, and the fifth pulse modulation circuit all serve as the third port;

[0019] The output end of the third digital-to-analog conversion circuit is connected to the input end of the fourth operational amplifier circuit, and the output end of the fourth operational amplifier circuit is connected to the control end of the second band-pass filter circuit; the output end of the fourth pulse modulation circuit is connected to the control end of the third switched phase-sensitive detection circuit, and the output end of the fifth pulse modulation circuit is connected to the control end of the fourth switched phase-sensitive detection circuit;

[0020] The compensation induction coil is connected to the input end of the second signal amplification circuit. The output end of the second signal amplification circuit is connected to the input end of the second band-pass filter circuit. The output end of the second band-pass filter circuit is respectively connected to the input end of the third switched-phase-sensitive detection circuit and the input end of the fourth switched-phase-sensitive detection circuit. The output end of the third switched-phase-sensitive detection circuit is connected to the input end of the third low-pass filter circuit. The output end of the third low-pass filter circuit is connected to the input end of the fifth operational amplifier circuit. The output end of the fifth operational amplifier circuit is connected to the input end of the third analog-to-digital conversion circuit. The output end of the fourth switched-phase-sensitive detection circuit is connected to the input end of the fourth low-pass filter circuit. The output end of the fourth low-pass filter circuit is connected to the input end of the sixth operational amplifier circuit. The output end of the sixth operational amplifier circuit is connected to the input end of the fourth analog-to-digital conversion circuit.

[0021] Optionally, the center frequency of the second band-pass filter circuit is adjusted based on the voltage amplitude output by the third digital-to-analog conversion circuit, and the center frequency of the second band-pass filter circuit is equal to the frequency of the pulse signals output by the fourth pulse modulation circuit and the fifth pulse modulation circuit.

[0022] Optionally, the device further includes an interference signal detection module, and the control module further includes a fourth port connected to the interference signal detection module;

[0023] Wherein, the interference signal detection module is used to obtain the frequency and amplitude of the interference signal, and transmit the frequency and amplitude of the interference signal to the control module through the fourth port.

[0024] Optionally, the interference signal detection module includes a current mutual inductance circuit, a seventh operational amplifier circuit, a filter circuit, a comparison circuit and a detection circuit; the induction signal conditioning module further includes an input capture circuit and a fifth analog-to-digital conversion circuit;

[0025] Wherein, the output end of the current mutual inductance circuit is connected to the input end of the seventh operational amplifier circuit. The output end of the seventh operational amplifier circuit is connected to the input end of the filter circuit. The output end of the filter circuit is respectively connected to the input end of the comparison circuit and the input end of the detection circuit. The output end of the comparison circuit is connected to the input end of the input capture circuit. The output end of the detection circuit is connected to the input end of the fifth analog-to-digital conversion circuit. The output ends of the input capture circuit and the fifth analog-to-digital conversion circuit are connected to the control unit.

[0026] In a second aspect, an embodiment of the present application provides a method for conditioning a signal of an electromagnetic sensing device. The method is applied to the electromagnetic sensing device described in the first aspect, and the method includes:

[0027] The excitation signal adjustment module adjusts the frequency and amplitude of the excitation signal according to the parameter value output from the second port, and outputs the adjusted excitation signal to the primary excitation coil, where the parameter value output from the second port is adjusted based on the parameter adjustment instruction received by the first port;

[0028] The primary excitation coil generates an alternating magnetic field according to the adjusted excitation signal;

[0029] The secondary induction coil generates an induction signal according to the alternating magnetic field;

[0030] The induction signal conditioning module conditions the induction signal according to the parameter value output from the third port to obtain a liquid level signal for characterizing the liquid level to be detected, where the parameter value output from the third port is adjusted based on the parameter adjustment instruction received by the first port.

[0031] Optionally, a second digital-to-analog conversion circuit, a second pulse modulation circuit, a third pulse modulation circuit, a first analog-to-digital conversion circuit, and a second analog-to-digital conversion circuit are further encapsulated in the control module; the induction signal conditioning module includes a first signal amplification circuit, a first operational amplification circuit, a first band-pass filter circuit, a first switched-phase sensitive demodulation circuit, a second switched-phase sensitive demodulation circuit, a first low-pass filter circuit, a second low-pass filter circuit, a second operational amplification circuit, and a third operational amplification circuit; the method further includes:

[0032] Obtain the signal output by the second analog-to-digital conversion circuit;

[0033] Take the signal output by the second analog-to-digital conversion circuit as a first feedback signal, and perform an overall shift on the phase of the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit relative to the phase of the pulse signal output by the first pulse modulation circuit, so that the first feedback signal has a voltage amplitude approaching zero, where the phase difference between the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit always remains at 90 degrees.

[0034] Optionally, the device further includes a compensation induction coil disposed near the secondary induction coil; a third digital-to-analog conversion circuit, a fourth pulse modulation circuit, a fifth pulse modulation circuit, a third analog-to-digital conversion circuit, and a fourth analog-to-digital conversion circuit are further encapsulated in the control module; the induction signal conditioning module further includes a second signal amplification circuit, a fourth operational amplification circuit, a second band-pass filter circuit, a third switched-phase sensitive demodulation circuit, a fourth switched-phase sensitive demodulation circuit, a third low-pass filter circuit, a fourth low-pass filter circuit, a fifth operational amplification circuit, and a sixth operational amplification circuit; the method further includes:

[0035] Obtain the signal output by the fourth analog-to-digital conversion circuit;

[0036] Use the signal output by the fourth analog-to-digital conversion circuit as the second feedback signal to globally shift the phases of the pulse signals output by the third pulse modulation circuit and the fourth pulse modulation circuit relative to the phase of the pulse signal output by the first pulse modulation circuit, so that the second feedback signal has a voltage amplitude approaching zero, where the phase difference between the pulse signals output by the third pulse modulation circuit and the fourth pulse modulation circuit is always maintained at 90 degrees.

[0037] Optionally, the method further includes:

[0038] The control unit obtains the first sampling signal obtained by the induction signal conditioning module after conditioning the secondary induction coil and the second sampling signal obtained by the induction signal conditioning module after conditioning the compensation induction coil, and performs zero-adjustment calibration on the first sampling signal and the second sampling signal to obtain a zero-adjustment calibration coefficient;

[0039] Determine an interference correction value according to the amplitude of the interference signal, and determine the filtering coefficient corresponding to the preset digital notch filter in the control unit according to the frequency of the interference signal;

[0040] Use the zero-adjustment calibration coefficient, the interference correction value, and the filtering coefficient to perform signal processing on the first sampling signal and the second sampling signal to obtain the liquid level signal.

[0041] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art: The electromagnetic sensing device provided by the embodiment of the present application includes: a control module, an excitation signal adjustment module, an induction signal conditioning module, a human-computer interaction module, and a primary excitation coil and a secondary induction coil arranged near the liquid level to be detected; wherein, the control module includes a first port connected to the human-computer interaction module, a second port connected to the excitation signal adjustment module, and a third port connected to the induction signal conditioning module; the excitation signal adjustment module is connected to the primary excitation coil, and the excitation signal adjustment module is configured to adjust the frequency and amplitude of the excitation signal according to the parameter value output by the second port, and output the adjusted excitation signal to the primary excitation coil, and the primary excitation coil is configured to generate an alternating magnetic field according to the adjusted excitation signal; the induction signal conditioning module is connected to the secondary induction coil, the secondary induction coil is configured to generate an induction signal according to the alternating magnetic field, and the induction signal conditioning module is configured to condition the induction signal according to the parameter value output by the third port to obtain a liquid level signal for characterizing the liquid level to be detected; the parameter value output by the second port and the parameter value output by the third port are adjusted based on the parameter adjustment instruction received by the first port. In this way, the parameter values output by the second port and the third port can be adjusted by the parameter adjustment instruction input by the human-computer interaction module, so as to flexibly adjust the frequency and amplitude of the excitation signal and the parameters required in the conditioning process of the induction signal, thereby effectively avoiding electromagnetic interference generated by various on-site devices and making the detection result of the liquid level to be detected more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present invention and, together with the specification, are used to explain the principles of the present invention.

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0044] One or more embodiments are exemplarily illustrated by the pictures in the corresponding accompanying drawings. These exemplary illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, unless otherwise stated, and the drawings in the drawings do not constitute a proportional limitation.

[0045] Figure 1 FIG. is a schematic structural diagram of an electromagnetic sensing device provided by an embodiment of the present application;

[0046] Figure 2 Schematic structural diagram of an electromagnetic sensing device provided in the related art;

[0047] Figure 3 Schematic structural diagram of another electromagnetic sensing device provided in an embodiment of the present application;

[0048] Figure 4 Schematic structural diagram of yet another electromagnetic sensing device provided in an embodiment of the present application;

[0049] Figure 5 Schematic structural diagram of another electromagnetic sensing device provided in an embodiment of the present application;

[0050] Figure 6 Schematic flow diagram of a signal conditioning method for an electromagnetic sensing device provided in an embodiment of the present application. Detailed implementation manners

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0052] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or letters in different examples. This repetition is for the purpose of simplification and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed.

[0053] To solve the problem that the accuracy of the detection result of the liquid level height of the existing electromagnetic sensor is relatively low, the present application provides an electromagnetic sensing device and its signal conditioning method, which can effectively avoid electromagnetic interference generated by various on-site devices and make the detection result of the liquid level to be detected more accurate.

[0054] See Figure 1 , Figure 1 Schematic structural diagram of an electromagnetic sensing device provided in an embodiment of the present application. As Figure 1 shown, the electromagnetic sensing device includes: a control module 100, an excitation signal adjustment module 200, an induction signal conditioning module 300, a human-machine interaction module 400, and a primary excitation coil and a secondary induction coil disposed near the liquid level to be detected;

[0055] Among them, the control module 100 includes a first port connected to the human-machine interaction module 400, a second port connected to the excitation signal adjustment module 200, and a third port connected to the induction signal conditioning module 300;

[0056] The excitation signal adjustment module 200 is connected to the primary excitation coil. The excitation signal adjustment module 200 is configured to adjust the frequency and amplitude of the excitation signal according to the parameter values output from the second port, and output the adjusted excitation signal to the primary excitation coil. The primary excitation coil is configured to generate an alternating magnetic field according to the adjusted excitation signal;

[0057] The induction signal conditioning module 300 is connected to the secondary induction coil. The secondary induction coil is configured to generate an induction signal according to the alternating magnetic field. The induction signal conditioning module 300 is configured to condition the induction signal according to the parameter values output from the third port to obtain a liquid level signal for characterizing the liquid level to be detected;

[0058] The parameter values output from the second port and the parameter values output from the third port are adjusted based on the parameter adjustment instructions received by the first port.

[0059] It should be noted that in addition to the Central Processing Unit (CPU), the above control module 100 may further include other circuits such as an analog-to-digital conversion circuit, a digital-to-analog conversion circuit, a pulse modulation circuit, etc. They are packaged together in a chip, and the input and output ports of these circuits correspond to different pins of the chip.

[0060] The setting directions, shapes, numbers of turns, etc. of the above primary excitation coil and secondary induction coil can be set according to actual needs and are not specifically limited herein. The primary excitation coil and the secondary induction coil can be a toroidal coil or a rectangular coil, etc. As an optional implementation manner, the central axis of the primary excitation coil and the central axis of the secondary induction coil can be perpendicular to each other. Specifically, the central axis of the primary excitation coil can be set parallel to the liquid level to be detected, and the central axis of the secondary induction coil can be set perpendicular to the plane of the liquid level to be detected, so that the amplitude of the induced electric field on the secondary induction coil is more sensitive to the change of the liquid level.

[0061] The above excitation signal adjustment module 200 can adjust the frequency and amplitude of the excitation signal (i.e., alternating current) according to the parameter values output from the second port, and output the adjusted excitation signal to the primary excitation coil. In this way, the primary excitation coil can generate an alternating magnetic field according to the adjusted excitation signal, and the secondary induction coil generates an alternating induced electric field in this alternating magnetic field. The alternating induced electric field then generates an eddy current (i.e., induced signal) in the closed loop and gives it to the induction signal conditioning module 300. At this time, the induction signal conditioning module 300 can condition the induction signal according to the parameter values output from the third port to obtain a liquid level signal for characterizing the liquid level to be detected.

[0062] In the related art, the amplitude of the excitation signal is usually obtained by dividing the voltage of a fixed voltage source using a potentiometer, and the frequency of the excitation signal is usually obtained by dividing the frequency of a fixed active crystal oscillator using a frequency division module. Therefore, the amplitude and frequency of the modulated excitation signal are usually fixed and non-adjustable. Moreover, when filtering the induction signal, a filter circuit with a fixed center frequency is usually used for filtering, and when amplitude modulating or phase modulating the induction signal, a potentiometer is usually used for adjustment, as Figure 2 shown. Since the amplitude and frequency of the excitation signal and the center frequency of the filter circuit are all fixed and cannot be adjusted online, and the potentiometer has a large temperature coefficient and is prone to causing drift of the detection result, the detection result of the existing electromagnetic sensor is not accurate enough.

[0063] However, in the embodiment of the present application, there is no need to use a potentiometer to adjust the induction signal, and the parameter values output from the second port and the third port can be adjusted by the parameter adjustment instruction input through the human-machine interaction module 400, so as to flexibly adjust the frequency and amplitude of the excitation signal and the parameters required in the conditioning process of the induction signal, thereby effectively avoiding the electromagnetic interference generated by various on-site devices and making the detection result of the liquid level to be detected more accurate.

[0064] Further, referring to Figure 3 , a control unit CPU, a first digital-to-analog conversion circuit DAC1, and a first pulse width modulation circuit PWM1 are encapsulated in the control module 100; the excitation signal adjustment module 200 includes a signal modulation circuit 201 and a power amplifier circuit 202;

[0065] Among them, the input ends of the first digital-to-analog conversion circuit DAC1 and the first pulse width modulation circuit PWM1 are both connected to the control unit CPU. The output ends of the first digital-to-analog conversion circuit DAC1 and the first pulse width modulation circuit PWM1 both serve as the second ports and are connected to the input end of the signal modulation circuit 201. The output end of the signal modulation circuit 201 is connected to the input end of the power amplifier circuit 202. The output end of the power amplifier circuit 202 is respectively connected to the feedback end of the signal modulation circuit 201 and the primary excitation coil.

[0066] Specifically, the above-mentioned first digital-to-analog conversion circuit DAC1 can adjust the voltage amplitude of the signal it outputs according to the voltage amplitude parameter set by the user, so as to achieve amplitude modulation of the signal in the modulation circuit. The above-mentioned first pulse width modulation circuit PWM1 microcontroller can adjust the frequency of the pulse signal it outputs according to the frequency parameter set by the user, so as to achieve frequency modulation of the signal in the modulation circuit. Then, after being modulated by the modulation circuit and amplified by the power amplifier circuit 202, an excitation signal similar to a sine wave with adjustable amplitude and frequency can be obtained and given to the primary excitation coil. In this way, the primary excitation coil can generate an alternating magnetic field according to this excitation signal.

[0067] Further, continue to refer to Figure 3 , a second digital-to-analog conversion circuit DAC2, a second pulse width modulation circuit PWM2, a third pulse width modulation circuit PWM3, a first analog-to-digital conversion circuit ADC1, and a second analog-to-digital conversion circuit ADC2 are also encapsulated in the control module 100; the induction signal conditioning module 300 includes a first signal amplifier circuit 301, a first operational amplifier circuit 302, a first band-pass filter circuit 303, a first switched-phase sensitive demodulation circuit 304, a second switched-phase sensitive demodulation circuit 305, a first low-pass filter circuit 306, a second low-pass filter circuit 307, a second operational amplifier circuit 308, and a third operational amplifier circuit 309;

[0068] Among them, the input ends of the second digital-to-analog conversion circuit DAC2, the second pulse width modulation circuit PWM2, the third pulse width modulation circuit PWM3, the output end of the first analog-to-digital conversion circuit ADC1, and the output end of the second analog-to-digital conversion circuit ADC2 are all connected to the control unit CPU. The output ends of the second digital-to-analog conversion circuit DAC2, the second pulse width modulation circuit PWM2, and the third pulse width modulation circuit PWM3 all serve as the third ports;

[0069] The output terminal of the second digital-to-analog conversion circuit DAC2 is connected to the input terminal of the first operational amplifier circuit 302, and the output terminal of the first operational amplifier circuit 302 is connected to the control terminal of the first band-pass filter circuit 303; the output terminal of the second pulse modulation circuit PWM2 is connected to the control terminal of the first switched phase-sensitive detection circuit 304, and the output terminal of the third pulse modulation circuit PWM3 is connected to the control terminal of the second switched phase-sensitive detection circuit 305;

[0070] The secondary induction coil is connected to the input terminal of the first signal amplification circuit 301, the output terminal of the first signal amplification circuit 301 is connected to the input terminal of the first band-pass filter circuit 303, the output terminal of the first band-pass filter circuit 303 is respectively connected to the input terminals of the first switched phase-sensitive detection circuit 304 and the second switched phase-sensitive detection circuit 305, the output terminal of the first switched phase-sensitive detection circuit 304 is connected to the input terminal of the first low-pass filter circuit 306, the output terminal of the first low-pass filter circuit 306 is connected to the input terminal of the second operational amplifier circuit 308, and the output terminal of the second operational amplifier circuit 308 is connected to the input terminal of the first analog-to-digital conversion circuit ADC1; the output terminal of the second switched phase-sensitive detection circuit 305 is connected to the input terminal of the second low-pass filter circuit 307, the output terminal of the second low-pass filter circuit 307 is connected to the input terminal of the third operational amplifier circuit 309, and the output terminal of the third operational amplifier circuit 309 is connected to the input terminal of the second analog-to-digital conversion circuit ADC2.

[0071] Specifically, the above-mentioned second digital-to-analog conversion circuit DAC2 can adjust the voltage amplitude of the output signal according to the voltage amplitude parameter set by the user. After the signal with the adjusted voltage amplitude is amplified by the first operational amplifier circuit 302, it is input to the first band-pass filter circuit 303 for voltage-controlled tracking, so as to change the filter center frequency of the first band-pass filter circuit 303 to be consistent with the frequency of the pulse signal output by the control module 100.

[0072] The above-mentioned second pulse modulation circuit PWM2 and third pulse modulation circuit PWM3 are respectively used to output pulse signals to their respective switched phase-sensitive detection circuits. The frequency of this pulse signal can be increased or decreased in accordance with a preset step according to the frequency parameter received by the first port of the control module 100, so as to adjust the frequency of the pulse signals output by the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3. It should be noted that the frequencies of the pulse signals output by the above-mentioned second pulse modulation circuit PWM2 and third pulse modulation circuit PWM3 need to be equal to the frequency of the pulse signal output by the above-mentioned first pulse modulation circuit PWM1, that is, equal to the center frequency of the first band-pass filter circuit 303. In addition, the pulse signals output by the above-mentioned second pulse modulation circuit PWM2 and third pulse modulation circuit PWM3 (that is Figure 3The phase difference between 0° and 90° of the A phase in [the text] is 90°. In an ideal state, the phase of the pulse signal output by the second pulse modulation circuit PWM2 is in phase with the induction signal input to the first switched phase-sensitive detector circuit 304, that is, the phase difference between the two is 0°. The phase of the pulse signal output by the second pulse modulation circuit PWM2 is orthogonal to the induction signal input to the first switched phase-sensitive detector circuit 304, that is, the phase difference between the two is 90°. However, due to interference signal interference and its own drift, there is often a phase deviation between the phase of the pulse signal output by the second pulse modulation circuit PWM2 and the induction signal input to the first switched phase-sensitive detector circuit 304, and there is also a phase deviation between the phase of the pulse signal output by the second pulse modulation circuit PWM2 and the induction signal input to the first switched phase-sensitive detector circuit 304. At this time, a nearly direct current signal obtained after phase-sensitive detection and low-pass filtering by the second analog-to-digital conversion circuit ADC2 can be used as a feedback signal (when this feedback signal is close to 0, it means that the phase of the pulse signal output by the third pulse modulation circuit PWM3 is orthogonal to the phase of the detected signal. When this feedback signal is positive or negative, the phase of the pulse signal output by the third pulse modulation circuit PWM3 is ahead of or lagging behind the phase of the detected signal). The control unit CPU can control the pulse signals output by the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3 according to the magnitude of this feedback information to maintain a 90° phase angle and move the phase of the pulse signal output by the first pulse modulation circuit PWM1 that is unchanged as a whole with respect to the frequency phase. In this way, proportional-integral-derivative (PID) closed-loop regulation can be carried out. Generally, the closed-loop control target is that the feedback signal is close to 0.

[0073] In this way, the phase difference between the pulse signal input to the first switched phase-sensitive detector circuit 304 and the input induction signal and the phase difference between the pulse signal input to the second switched phase-sensitive detector circuit 305 and the input induction signal can be closed-loop controlled and locked. After the phase changes due to electromagnetic interference at the front end, it can be automatically corrected in real time, reducing the deviation of the finally output liquid level signal and increasing the anti-interference ability of the electromagnetic sensing device detection.

[0074] Furthermore, the center frequency of the first band-pass filter circuit 303 is adjusted based on the voltage amplitude output by the second digital-to-analog conversion circuit DAC2, and the center frequency of the first band-pass filter circuit 303 is equal to the frequencies of the pulse signals output by the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3.

[0075] Specifically, the above-mentioned second digital-to-analog conversion circuit DAC2 can adjust the voltage amplitude of the signal it outputs according to the voltage amplitude parameter set by the user. After the voltage amplitude of the signal is adjusted, it is amplified by the first operational amplifier circuit 302 and then input to the first band-pass filter circuit 303 for voltage-controlled tracking, thereby changing the filter center frequency of the first band-pass filter circuit 303 to make it consistent with the frequency of the pulse signal output by the control module 100. In this way, the first band-pass filter circuit 303 can effectively filter out the interference signals in the induction signal, improving the accuracy of the detection result of the electromagnetic sensing device.

[0076] Further, the control unit CPU is used to use the signal output by the second analog-to-digital conversion circuit ADC2 as the first feedback signal to integrally shift the phases of the pulse signals output by the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3 relative to the phase of the pulse signal output by the first pulse modulation circuit PWM1, so that the first feedback signal has a voltage amplitude approaching zero. Among them, the phase difference between the pulse signals output by the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3 always remains at 90 degrees.

[0077] Specifically, after receiving the signal output by the second analog-to-digital conversion circuit ADC2, the control unit CPU can use this signal as the first feedback signal to integrally shift the phases of the pulse signals output by the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3 relative to the phase of the pulse signal output by the first pulse modulation circuit PWM1, so that the first feedback signal has a voltage amplitude approaching zero. In this way, it is possible to achieve closed-loop control locking of the phase difference between the pulse signal input to the first switched-phase sensitive demodulation circuit 304 and the input induction signal and the phase difference between the pulse signal input to the second switched-phase sensitive demodulation circuit 305 and the input induction signal. When the phase changes due to electromagnetic interference at the front end, it can be automatically corrected in real time, reducing the deviation of the finally output liquid level signal and increasing the anti-interference ability of the electromagnetic sensing device detection.

[0078] Further, continue to refer to Figure 3 , the device further includes a compensation induction coil disposed near the secondary induction coil; a third digital-to-analog conversion circuit DAC3, a fourth pulse modulation circuit PWM4, a fifth pulse modulation circuit PWM5, a third analog-to-digital conversion circuit ADC3, and a fourth analog-to-digital conversion circuit ADC4 are further encapsulated in the control module 100; the induction signal conditioning module 300 further includes a second signal amplifier circuit 310, a fourth operational amplifier circuit 311, a second band-pass filter circuit 312, a third switched-phase sensitive demodulation circuit 313, a fourth switched-phase sensitive demodulation circuit 314, a third low-pass filter circuit 315, a fourth low-pass filter circuit 316, a fifth operational amplifier circuit 317, and a sixth operational amplifier circuit 318;

[0079] Among them, the input end of the third digital-to-analog conversion circuit DAC3, the input end of the fourth pulse modulation circuit PWM4, the input end of the fifth pulse modulation circuit PWM5, the output end of the third analog-to-digital conversion circuit ADC3, and the output end of the fourth analog-to-digital conversion circuit ADC4 are all connected to the control unit CPU. The output ends of the third digital-to-analog conversion circuit DAC3, the fourth pulse modulation circuit PWM4, and the fifth pulse modulation circuit PWM5 all serve as the third port;

[0080] The output end of the third digital-to-analog conversion circuit DAC3 is connected to the input end of the fourth operational amplifier circuit 311. The output end of the fourth operational amplifier circuit 311 is connected to the control end of the second band-pass filter circuit 312. The output end of the fourth pulse modulation circuit PWM4 is connected to the control end of the third switched-phase-sensitive detection circuit 313. The output end of the fifth pulse modulation circuit PWM5 is connected to the control end of the fourth switched-phase-sensitive detection circuit 314;

[0081] The compensation induction coil is connected to the input end of the second signal amplification circuit 310. The output end of the second signal amplification circuit 310 is connected to the input end of the second band-pass filter circuit 312. The output end of the second band-pass filter circuit 312 is respectively connected to the input ends of the third switched-phase-sensitive detection circuit 313 and the fourth switched-phase-sensitive detection circuit 314. The output end of the third switched-phase-sensitive detection circuit 313 is connected to the input end of the third low-pass filter circuit 315. The output end of the third low-pass filter circuit 315 is connected to the input end of the fifth operational amplifier circuit 317. The output end of the fifth operational amplifier circuit 317 is connected to the input end of the third analog-to-digital conversion circuit ADC3. The output end of the fourth switched-phase-sensitive detection circuit 314 is connected to the input end of the fourth low-pass filter circuit 316. The output end of the fourth low-pass filter circuit 316 is connected to the input end of the sixth operational amplifier circuit 318. The output end of the sixth operational amplifier circuit 318 is connected to the input end of the fourth analog-to-digital conversion circuit ADC4.

[0082] Specifically, the above-mentioned third digital-to-analog conversion circuit DAC3 can adjust the voltage amplitude of the signal it outputs according to the voltage amplitude parameter set by the user. After the signal with the adjusted voltage amplitude is operationally amplified by the fourth operational amplifier circuit 311, it is input to the second band-pass filter circuit 312 for voltage-controlled tracking, so as to change the filter center frequency of the second band-pass filter circuit 312 to be consistent with the frequency of the pulse signal output by the control module 100.

[0083] The above-mentioned fourth pulse modulation circuit PWM4 and fifth pulse modulation circuit PWM5 are respectively used to output pulse signals to their respective switch phase-sensitive demodulation circuits. The frequency of the pulse signal can be varied by increasing or decreasing the frequency according to the frequency parameter received by the first port of the control module 100 in a preset step, so as to adjust the frequencies of the pulse signals output by the fourth pulse modulation circuit PWM4 and the fifth pulse modulation circuit PWM5. It should be noted that the frequencies of the pulse signals output by the above-mentioned fourth pulse modulation circuit PWM4 and fifth pulse modulation circuit PWM5 need to be equal to the frequency of the pulse signal output by the above-mentioned first pulse modulation circuit PWM1, that is, equal to the center frequency of the second band-pass filter circuit 312. In addition, the phases of the pulse signals output by the above-mentioned fourth pulse modulation circuit PWM4 and fifth pulse modulation circuit PWM5 (i.e., Figure 3 the 0° of the B phase and the 90° of the B phase in

[0084] are 90° out of phase. In an ideal state, the phase of the pulse signal output by the fourth pulse modulation circuit PWM4 is in phase with the induced signal input to the third switch phase-sensitive demodulation circuit 313, that is, the phase difference between the two is 0°. The phase of the pulse signal output by the fifth pulse modulation circuit PWM5 is orthogonal to the induced signal input to the fourth switch phase-sensitive demodulation circuit 314, that is, the phase difference between the two is 90°. However, due to the interference of interference signals and the existence of drift, there is often a phase deviation between the phase of the pulse signal output by the fourth pulse modulation circuit PWM4 and the induced signal input to the third switch phase-sensitive demodulation circuit 313, and there is also a phase deviation between the phase of the pulse signal output by the fifth pulse modulation circuit PWM5 and the induced signal input to the fourth switch phase-sensitive demodulation circuit 314. At this time, a nearly direct current signal obtained by phase-sensitive demodulation and low-pass filtering collected by the fourth analog-to-digital conversion circuit ADC4 can be used as a feedback signal (when the feedback signal is close to 0, it means that the phase of the pulse signal output by the fifth pulse modulation circuit PWM5 is orthogonal to the phase of the signal to be detected. When the feedback signal is positive or negative, the phase of the pulse signal output by the fifth pulse modulation circuit PWM5 is ahead of or lags behind the phase of the signal to be detected). The control unit CPU can control the pulse signals output by the fourth pulse modulation circuit PWM4 and the fifth pulse modulation circuit PWM5 to maintain a 90° phase angle and move the phase of the pulse signal output by the first pulse modulation circuit PWM1 with an overall unchanged relative frequency phase according to the magnitude of the feedback information. In this way, proportional-integral-derivative (PID) closed-loop regulation can be performed. Generally, the closed-loop control target is that the feedback signal is close to 0.In this way, it is possible to achieve closed-loop control and locking of the phase differences between the pulse signals input to the third switched-phase sensitive demodulation circuit 313 and the induced signals input thereto, and between the pulse signals input to the fourth switched-phase sensitive demodulation circuit 314 and the induced signals input thereto. After the phase changes due to electromagnetic interference at the front end, real-time automatic correction can be performed to reduce the deviation of the finally output liquid level signal and enhance the anti-interference ability of the electromagnetic sensing device detection.

[0085] Further, the center frequency of the second band-pass filter circuit 312 is adjusted based on the voltage amplitude output by the third digital-to-analog conversion circuit DAC3, and the center frequency of the second band-pass filter circuit 312 is equal to the frequencies of the pulse signals output by the fourth pulse modulation circuit PWM4 and the fifth pulse modulation circuit PWM5.

[0086] Specifically, the above-mentioned third digital-to-analog conversion circuit DAC3 can adjust the voltage amplitude of the signal it outputs according to the voltage amplitude parameter set by the user. After the signal with the adjusted voltage amplitude is operationally amplified by the fourth operational amplifier circuit 311, it is input to the second band-pass filter circuit 312 for voltage-controlled tracking, thereby changing the filtering center frequency of the second band-pass filter circuit 312 to make it consistent with the frequency of the pulse signal output by the control module 100. In this way, the second band-pass filter circuit 312 can effectively filter out the interference signals in the induced signals, improving the accuracy of the detection results of the electromagnetic sensing device.

[0087] Further, the control unit CPU is used to use the signal output by the fourth analog-to-digital conversion circuit ADC4 as the second feedback signal to globally shift the phases of the pulse signals output by the third pulse modulation circuit PWM3 and the fourth pulse modulation circuit PWM4 relative to the phase of the pulse signal output by the first pulse modulation circuit PWM1, so that the second feedback signal has a voltage amplitude approaching zero, wherein the phase difference between the pulse signals output by the third pulse modulation circuit PWM3 and the fourth pulse modulation circuit PWM4 always remains at 90 degrees.

[0088] Specifically, after receiving the signal output by the fourth analog-to-digital conversion circuit ADC4, the control unit CPU can use this signal as the second feedback signal to globally shift the phases of the pulse signals output by the fourth pulse modulation circuit PWM4 and the fifth pulse modulation circuit PWM5 relative to the phase of the pulse signal output by the first pulse modulation circuit PWM1, so that the second feedback signal has a voltage amplitude approaching zero. In this way, it is possible to achieve closed-loop control and locking of the phase differences between the pulse signals input to the third switched-phase sensitive demodulation circuit 313 and the input induction signal, and between the pulse signals input to the fourth switched-phase sensitive demodulation circuit 314 and the input induction signal. When the phase changes due to electromagnetic interference at the front end, it can be automatically corrected in real time, reducing the deviation generated in the final output liquid level signal and increasing the anti-interference ability of the electromagnetic sensing device.

[0089] Further, referring to Figure 4 , the device further includes an interference signal detection module 500, and the control module 100 further includes a fourth port connected to the interference signal detection module 500;

[0090] Among them, the interference signal detection module 500 is used to obtain the frequency and amplitude of the interference signal, and transmit the frequency and amplitude of the interference signal to the control module 100 through the fourth port.

[0091] In an embodiment, the interference signal detection module 500 can also be used to obtain the frequency and amplitude of the interference signal, and calculate the interference correction value and the filtering coefficient corresponding to the digital notch filter according to the obtained frequency and amplitude of the interference signal, which is convenient for subsequently reducing the deviation and fluctuation generated in the liquid level signal according to the interference correction value and the filtering coefficient corresponding to the digital notch filter, thereby increasing the anti-interference ability of the electromagnetic sensing device.

[0092] Further, referring to Figure 5 , the interference signal detection module 500 includes a current mutual inductance circuit 501, a seventh operational amplifier circuit 502, a filtering circuit 503, a comparison circuit 504, and a detection circuit 505; the induction signal conditioning module 300 further includes an input capture circuit IC1 and a fifth analog-to-digital conversion circuit ADC5;

[0093] Among them, the output end of the current mutual inductance circuit 501 is connected to the input end of the seventh operational amplifier circuit 502, the output end of the seventh operational amplifier circuit 502 is connected to the input end of the filtering circuit 503, the output end of the filtering circuit 503 is respectively connected to the input end of the comparison circuit 504 and the input end of the detection circuit 505, the output end of the comparison circuit 504 is connected to the input end of the input capture circuit IC1, the output end of the detection circuit 505 is connected to the input end of the fifth analog-to-digital conversion circuit ADC5, and the output ends of the input capture circuit IC1 and the fifth analog-to-digital conversion circuit ADC5 are connected to the control unit CPU.

[0094] In one embodiment, a current mutual inductance circuit 501 can also be used to detect the current mutual inductance signal output by an external electromagnetic interference generating device. After being amplified by a seventh operational amplifier circuit 502 and filtered by a filter circuit 503, the signal is then input into an input capture circuit IC1 through a comparison circuit 504. The input capture circuit IC1 obtains the frequency of the interference signal, and the signal is input into a fifth analog-to-digital conversion circuit ADC5 through a detection circuit 505. The fifth analog-to-digital conversion circuit ADC5 obtains the amplitude of the interference signal. According to the obtained frequency and amplitude of the interference signal, the electromagnetic sensing device can be better adjusted to actively avoid interference or add an interference correction value to correct the error in the final liquid level calculation. Also, a reasonable filtering coefficient of a digital notch filter can be selected in the control unit CPU to better filter out interference from the final liquid level result while maintaining a good response speed.

[0095] It should be noted that the input capture circuit IC1 can be set to capture the pulse width, and the pulse width here is recorded by the count value of the connected timer. The number of pulses within a cycle time can be obtained through the count value to determine the frequency of the interference signal. The fifth analog-to-digital conversion circuit ADC5 can sample the AC effective value or peak voltage of the processed current mutual inductance signal, and then multiply the measured AC effective value or peak voltage by a proportional value to obtain the actual AC effective value or peak voltage (i.e., the amplitude of the interference signal) of the device under test (i.e., the electromagnetic interference generating device).

[0096] See Figure 6 , Figure 6 is a schematic flowchart of a signal conditioning method for an electromagnetic sensing device provided by an embodiment of the present application. As Figure 6 shown, the signal conditioning method of the electromagnetic sensing device is applied to the above electromagnetic sensing device, and the method includes:

[0097] Step 601, an excitation signal adjustment module adjusts the frequency and amplitude of the excitation signal according to the parameter value output by the second port, and outputs the adjusted excitation signal to the primary excitation coil, where the parameter value output by the second port is adjusted based on the parameter adjustment instruction received by the first port;

[0098] Step 602, the primary excitation coil generates an alternating magnetic field according to the adjusted excitation signal;

[0099] Step 603, the secondary induction coil generates an induction signal according to the alternating magnetic field;

[0100] Step 604, the induction signal conditioning module conditions the induction signal according to the parameter value output by the third port to obtain a liquid level signal for characterizing the liquid level to be detected, where the parameter value output by the third port is adjusted based on the parameter adjustment instruction received by the first port.

[0101] In the related art, the amplitude of the excitation signal is usually obtained by dividing the voltage of a fixed voltage source using a potentiometer, and the frequency of the excitation signal is usually obtained by dividing the frequency of a fixed active crystal oscillator using a frequency division module. Therefore, the amplitude and frequency of the modulated excitation signal are usually fixed and non-adjustable. Moreover, when filtering the induction signal, a filter circuit with a fixed center frequency is usually used for filtering, and when amplitude modulating or phase modulating the induction signal, a potentiometer is usually used for adjustment, as Figure 2 shown. Since the amplitude and frequency of the excitation signal and the center frequency of the filter circuit are all fixed and cannot be adjusted online, and the potentiometer has a large temperature coefficient and is prone to causing drift in the detection result, the detection result of the existing electromagnetic sensor is not accurate enough.

[0102] In the embodiment of the present application, there is no need to use a potentiometer to adjust the induction signal, and the parameter values output by the second port and the third port can be adjusted through the parameter adjustment instruction input by the human-computer interaction module, so as to flexibly adjust the frequency and amplitude of the excitation signal and the parameters required in the conditioning process of the induction signal, thereby effectively avoiding electromagnetic interference generated by various on-site devices and making the detection result of the liquid level to be detected more accurate.

[0103] Further, as Figure 3 shown, a second digital-to-analog conversion circuit, a second pulse modulation circuit, a third pulse modulation circuit, a first analog-to-digital conversion circuit, and a second analog-to-digital conversion circuit are also encapsulated in the control module; the induction signal conditioning module includes a first signal amplification circuit, a first operational amplification circuit, a first band-pass filter circuit, a first switched-phase-sensitive demodulation circuit, a second switched-phase-sensitive demodulation circuit, a first low-pass filter circuit, a second low-pass filter circuit, a second operational amplification circuit, and a third operational amplification circuit; the method further includes:

[0104] Obtain the signal output by the second analog-to-digital conversion circuit;

[0105] Use the signal output by the second analog-to-digital conversion circuit as a first feedback signal to globally shift the phase of the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit relative to the phase of the pulse signal output by the first pulse modulation circuit, so that the first feedback signal has a voltage amplitude approaching zero, where the phase difference between the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit always remains at 90 degrees.

[0106] In one embodiment, after receiving the signal output by the second analog-to-digital conversion circuit, the control unit may use this signal as the first feedback signal to globally shift the phases of the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit relative to the phase of the pulse signal output by the first pulse modulation circuit, so that the first feedback signal has a voltage amplitude approaching zero. In this way, it is possible to achieve closed-loop control locking of the phase difference between the pulse signal input to the first switched-phase sensitive demodulation circuit and the induced signal, and the phase difference between the pulse signal input to the second switched-phase sensitive demodulation circuit and the induced signal. When the phase changes due to electromagnetic interference at the front end, it can be automatically corrected in real time, reducing the deviation of the finally output liquid level signal and increasing the anti-interference ability of the electromagnetic sensing device for detection.

[0107] Further, the electromagnetic sensing device further includes a compensation induction coil disposed near the secondary induction coil; the control module further encapsulates a third digital-to-analog conversion circuit, a fourth pulse modulation circuit, a fifth pulse modulation circuit, a third analog-to-digital conversion circuit, and a fourth analog-to-digital conversion circuit; the induction signal conditioning module further includes a second signal amplification circuit, a fourth operational amplifier circuit, a second band-pass filter circuit, a third switched-phase sensitive demodulation circuit, a fourth switched-phase sensitive demodulation circuit, a third low-pass filter circuit, a fourth low-pass filter circuit, a fifth operational amplifier circuit, and a sixth operational amplifier circuit; the method further includes:

[0108] Obtain the signal output by the fourth analog-to-digital conversion circuit;

[0109] Use the signal output by the fourth analog-to-digital conversion circuit as the second feedback signal to globally shift the phases of the pulse signals output by the third pulse modulation circuit and the fourth pulse modulation circuit relative to the phase of the pulse signal output by the first pulse modulation circuit, so that the second feedback signal has a voltage amplitude approaching zero, wherein the phase difference between the pulse signals output by the third pulse modulation circuit and the fourth pulse modulation circuit is always maintained at 90 degrees.

[0110] In one embodiment, after receiving the signal output by the fourth analog-to-digital conversion circuit, the control unit may also use this signal as the second feedback signal to globally shift the phases of the pulse signals output by the fourth pulse modulation circuit and the fifth pulse modulation circuit relative to the phase of the pulse signal output by the first pulse modulation circuit, so that the second feedback signal has a voltage amplitude approaching zero. In this way, it is possible to achieve closed-loop control locking of the phase difference between the pulse signal input to the third switched-phase sensitive demodulation circuit and the induced signal, and the phase difference between the pulse signal input to the fourth switched-phase sensitive demodulation circuit and the induced signal. When the phase changes due to electromagnetic interference at the front end, it can be automatically corrected in real time, reducing the deviation of the finally output liquid level signal and increasing the anti-interference ability of the electromagnetic sensing device for detection.

[0111] Further, the method further includes:

[0112] The control unit obtains a first sampling signal obtained by the induction signal conditioning module after conditioning the signal of the secondary induction coil and a second sampling signal obtained by the induction signal conditioning module after conditioning the signal of the compensation induction coil, and performs zero adjustment and calibration on the first sampling signal and the second sampling signal to obtain a zero adjustment and calibration coefficient;

[0113] Determine an interference correction value according to the amplitude of the interference signal, and determine a filtering coefficient corresponding to a preset digital notch filter in the control unit according to the frequency of the interference signal;

[0114] Use the zero adjustment and calibration coefficient, the interference correction value, and the filtering coefficient to perform signal processing on the first sampling signal and the second sampling signal to obtain a liquid level signal.

[0115] Specifically, before using the electromagnetic sensing device for liquid level detection, the electromagnetic sensing device can be zero-adjusted and calibrated, so that the following relationship is satisfied between the first sampling signal and the second sampling signal:

[0116] Vs - K×Vc = 0;

[0117] Wherein, Vs represents the first sampling signal, Vc represents the second sampling signal, and K is the zero adjustment and calibration coefficient. Compared with Figure 2 implementing zero adjustment in the superimposing and amplifying module (that is, using the induction signal of the compensation induction coil as the signal source, adjusting two potentiometers to obtain two amplitude-modulated and phase-modulated AC signals that are superimposed and then canceled with the induction signal of the secondary induction coil to achieve zero adjustment), the zero adjustment method in the present application can reduce the interference signals mixed in, thereby improving the detection signal-to-noise ratio and the stability of the electromagnetic sensing device.

[0118] It should be noted that the first sampling signal Vs is the corresponding sampling signal obtained after the induction signal of the secondary induction coil passes through band-pass filtering, switching phase-sensitive detection, and low-pass filtering, and the first sampling signal Vs can be determined by the signals output by the first analog-to-digital conversion circuit and the second analog-to-digital conversion circuit. The second sampling signal Vc is the corresponding sampling signal obtained after the induction signal of the compensation induction coil passes through band-pass filtering, switching phase-sensitive detection, and low-pass filtering, and the second sampling signal Vc can be determined by the signals output by the third analog-to-digital conversion circuit and the fourth analog-to-digital conversion circuit. After the control unit determines the first sampling signal Vs according to the signals output by the first analog-to-digital conversion circuit and the second analog-to-digital conversion circuit, and determines the second sampling signal Vc according to the signals output by the third analog-to-digital conversion circuit and the fourth analog-to-digital conversion circuit, the zero adjustment and calibration coefficient K can be calculated using the above formula.

[0119] During the process of using the electromagnetic sensing device for liquid level detection, the interference signal detection module can be used to obtain the frequency and amplitude of the interference signal. Then, the interference correction value can be determined according to the amplitude of the interference signal, and the filtering coefficient corresponding to the preset digital notch filter in the control unit can be determined according to the frequency of the interference signal. Specifically, the following formula can be used to determine the interference correction value:

[0120] C = a×Co + b;

[0121] Where a and b are parameters obtained by fitting experimental data. Co is the AC effective value or peak voltage detected by the fifth analog-to-digital conversion circuit when there is an external current mutual inductance signal input, and is a manually adjustable parameter in the control unit when there is no external current transformer signal input.

[0122] Since the electromagnetic interference actually received by the electromagnetic sensing device not only corresponds to a DC error value but also has AC fluctuation interference, the digital notch filter can effectively filter out the AC interference loaded on the DC signal corresponding to the output liquid level without affecting the DC component and response speed. The digital notch filter here can be a filter equation in the control unit. The filtering coefficients of the filter equation are pre-calculated by matlab and stored in the memory of the control module. The control unit looks up the table according to the frequency of the interference signal obtained from the input capture circuit, and then loads the filtering coefficient corresponding to the digital notch filter from the memory of the control module.

[0123] Finally, the control unit can perform signal processing on the first sampling signal and the second sampling signal by using the zero adjustment calibration coefficient and the interference correction value. The processing process is: Vs - K×Vc + K×C. Then, the processed signal is filtered by the digital notch filter and the liquid level signal is output.

[0124] In this embodiment, the electromagnetic sensing device can adjust the frequency and amplitude of the excitation signal of the primary excitation coil and the center frequency of the band-pass filter circuit of the induction signal online according to the actual electromagnetic interference situation at the application site, effectively avoiding the interference caused by the continuously increasing electromagnetic stirring, electromagnetic braking and other equipment at the application site of the liquid level gauge to the electromagnetic sensing device, thereby improving the signal-to-noise ratio and anti-interference ability of the detection of the electromagnetic sensing device. Moreover, the phase difference between the carrier wave of the switched-phase sensitive demodulation circuit in the electromagnetic sensing device and the input induction signal is locked by closed-loop control. After the phase changes due to electromagnetic interference at the front end, it can be automatically corrected in real time, reducing the deviation of the finally output liquid level signal and increasing the anti-interference ability of the electromagnetic sensing device. In addition, the electromagnetic sensing device can detect the current mutual induction signal output by the equipment generating electromagnetic interference. After being collected and analyzed by the signal processing and control module, the interference correction value and digital notch processing are added to the final liquid level calculation, reducing the deviation and fluctuation of the finally output liquid level signal and further increasing the anti-interference ability of the electromagnetic sensing device. Again, the original potentiometer is removed from the electromagnetic sensing device, reducing the drift degree of the detection result, which is beneficial to enhancing the stability of the electromagnetic sensing device and improving the detection accuracy. Finally, the electromagnetic sensing device can also measure the phase difference between the excitation signal of the primary excitation coil and the induction signals of the secondary induction coil and the compensation induction coil in real time, providing more possibilities for the measurement system design based on the 3-coil electromagnetic detection principle.

[0125] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0126] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the essence of the above technical solution or the part that contributes to the related technology can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., including several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0127] It should be understood that the terms used herein are for the purpose of describing particular example embodiments only and are not intended to be limiting. Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" as used herein may also include the plural forms. The terms "comprising", "including", "containing", and "having" are inclusive and thus specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the particular order described or illustrated, unless an execution order is explicitly stated. It should also be understood that additional or alternative steps may be used.

[0128] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. An electromagnetic sensing device, characterized in that, The electromagnetic sensing device includes: a control module, an excitation signal adjustment module, an induction signal conditioning module, a human-computer interaction module, and a primary excitation coil and a secondary induction coil disposed near the liquid level to be detected; Among them, the control module includes a first port connected to the human-computer interaction module, a second port connected to the excitation signal adjustment module, and a third port connected to the induction signal conditioning module; The excitation signal adjustment module is connected to the primary excitation coil. The excitation signal adjustment module is configured to adjust the frequency and amplitude of the excitation signal according to the parameter value output from the second port, and output the adjusted excitation signal to the primary excitation coil. The primary excitation coil is configured to generate an alternating magnetic field according to the adjusted excitation signal; The induction signal conditioning module is connected to the secondary induction coil. The secondary induction coil is configured to generate an induction signal according to the alternating magnetic field. The induction signal conditioning module is configured to condition the induction signal according to the parameter value output from the third port to obtain a liquid level signal for characterizing the liquid level to be detected; The parameter value output from the second port and the parameter value output from the third port are adjusted based on the parameter adjustment instruction received by the first port; Among them, a control unit, a first digital-to-analog conversion circuit, and a first pulse modulation circuit are encapsulated in the control module; the excitation signal adjustment module includes a modulation circuit and a power amplification circuit; Among them, the input end of the first digital-to-analog conversion circuit and the input end of the first pulse modulation circuit are both connected to the control unit. The output end of the first digital-to-analog conversion circuit and the output end of the first pulse modulation circuit both serve as the second port and are connected to the input end of the modulation circuit. The output end of the modulation circuit is connected to the input end of the power amplification circuit. The output end of the power amplification circuit is respectively connected to the feedback end of the modulation circuit and the primary excitation coil; A second digital-to-analog conversion circuit, a second pulse modulation circuit, a third pulse modulation circuit, a first analog-to-digital conversion circuit, and a second analog-to-digital conversion circuit are also encapsulated in the control module; the induction signal conditioning module includes a first signal amplification circuit, a first operational amplification circuit, a first band-pass filter circuit, a first switched-phase-sensitive demodulation circuit, a second switched-phase-sensitive demodulation circuit, a first low-pass filter circuit, a second low-pass filter circuit, a second operational amplification circuit, and a third operational amplification circuit; Among them, the input end of the second digital-to-analog conversion circuit, the input end of the second pulse modulation circuit, the input end of the third pulse modulation circuit, the output end of the first analog-to-digital conversion circuit, and the output end of the second analog-to-digital conversion circuit are all connected to the control unit. The output end of the second digital-to-analog conversion circuit, the output end of the second pulse modulation circuit, and the output end of the third pulse modulation circuit all serve as the third port; The output terminal of the second digital-to-analog conversion circuit is connected to the input terminal of the first operational amplifier circuit, and the output terminal of the first operational amplifier circuit is connected to the control terminal of the first band-pass filter circuit; the output terminal of the second pulse modulation circuit is connected to the control terminal of the first switched-phase-sensitive demodulation circuit, and the output terminal of the third pulse modulation circuit is connected to the control terminal of the second switched-phase-sensitive demodulation circuit; The secondary induction coil is connected to the input terminal of the first signal amplification circuit, the output terminal of the first signal amplification circuit is connected to the input terminal of the first band-pass filter circuit, the output terminal of the first band-pass filter circuit is respectively connected to the input terminals of the first switched-phase-sensitive demodulation circuit and the second switched-phase-sensitive demodulation circuit, the output terminal of the first switched-phase-sensitive demodulation circuit is connected to the input terminal of the first low-pass filter circuit, the output terminal of the first low-pass filter circuit is connected to the input terminal of the second operational amplifier circuit, and the output terminal of the second operational amplifier circuit is connected to the input terminal of the first analog-to-digital conversion circuit; the output terminal of the second switched-phase-sensitive demodulation circuit is connected to the input terminal of the second low-pass filter circuit, the output terminal of the second low-pass filter circuit is connected to the input terminal of the third operational amplifier circuit, and the output terminal of the third operational amplifier circuit is connected to the input terminal of the second analog-to-digital conversion circuit.

2. The electromagnetic sensing device according to claim 1, characterized in that, The center frequency of the first band-pass filter circuit is adjusted based on the voltage amplitude output by the second digital-to-analog conversion circuit, and the center frequency of the first band-pass filter circuit is equal to the frequencies of the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit.

3. The electromagnetic sensing device according to claim 1, characterized in that, The device further includes a compensation induction coil disposed near the secondary induction coil; a third digital-to-analog conversion circuit, a fourth pulse modulation circuit, a fifth pulse modulation circuit, a third analog-to-digital conversion circuit, and a fourth analog-to-digital conversion circuit are further encapsulated in the control module; the induction signal conditioning module further includes a second signal amplification circuit, a fourth operational amplifier circuit, a second band-pass filter circuit, a third switched-phase-sensitive demodulation circuit, a fourth switched-phase-sensitive demodulation circuit, a third low-pass filter circuit, a fourth low-pass filter circuit, a fifth operational amplifier circuit, and a sixth operational amplifier circuit; Wherein, the input terminals of the third digital-to-analog conversion circuit, the fourth pulse modulation circuit, the fifth pulse modulation circuit, the output terminal of the third analog-to-digital conversion circuit, and the output terminal of the fourth analog-to-digital conversion circuit are all connected to the control unit, and the output terminals of the third digital-to-analog conversion circuit, the fourth pulse modulation circuit, and the fifth pulse modulation circuit all serve as the third port; The output terminal of the third digital-to-analog conversion circuit is connected to the input terminal of the fourth operational amplifier circuit, and the output terminal of the fourth operational amplifier circuit is connected to the control terminal of the second band-pass filter circuit; the output terminal of the fourth pulse modulation circuit is connected to the control terminal of the third switched-phase-sensitive demodulation circuit, and the output terminal of the fifth pulse modulation circuit is connected to the control terminal of the fourth switched-phase-sensitive demodulation circuit; The compensation induction coil is connected to the input end of the second signal amplification circuit. The output end of the second signal amplification circuit is connected to the input end of the second band-pass filtering circuit. The output end of the second band-pass filtering circuit is respectively connected to the input ends of the third switched-phase-sensitive detection circuit and the fourth switched-phase-sensitive detection circuit. The output end of the third switched-phase-sensitive detection circuit is connected to the input end of the third low-pass filtering circuit. The output end of the third low-pass filtering circuit is connected to the input end of the fifth operational amplifier circuit. The output end of the fifth operational amplifier circuit is connected to the input end of the third analog-to-digital conversion circuit. The output end of the fourth switched-phase-sensitive detection circuit is connected to the input end of the fourth low-pass filtering circuit. The output end of the fourth low-pass filtering circuit is connected to the input end of the sixth operational amplifier circuit. The output end of the sixth operational amplifier circuit is connected to the input end of the fourth analog-to-digital conversion circuit.

4. The electromagnetic sensing device according to claim 3, wherein, The center frequency of the second band-pass filtering circuit is adjusted based on the voltage amplitude output by the third digital-to-analog conversion circuit, and the center frequency of the second band-pass filtering circuit is equal to the frequencies of the pulse signals output by the fourth pulse modulation circuit and the fifth pulse modulation circuit.

5. The electromagnetic sensing device according to claim 3, wherein The device further includes an interference signal detection module, and the control module further includes a fourth port connected to the interference signal detection module. Wherein, the interference signal detection module is configured to obtain the frequency and amplitude of the interference signal, and transmit the frequency and amplitude of the interference signal to the control module through the fourth port.

6. The electromagnetic sensing device according to claim 5, characterized in that, The interference signal detection module includes a current mutual inductance circuit, a seventh operational amplifier circuit, a filtering circuit, a comparison circuit, and a detection circuit. The induction signal conditioning module further includes an input capture circuit and a fifth analog-to-digital conversion circuit. Wherein, the output end of the current mutual inductance circuit is connected to the input end of the seventh operational amplifier circuit. The output end of the seventh operational amplifier circuit is connected to the input end of the filtering circuit. The output end of the filtering circuit is respectively connected to the input ends of the comparison circuit and the detection circuit. The output end of the comparison circuit is connected to the input end of the input capture circuit. The output end of the detection circuit is connected to the input end of the fifth analog-to-digital conversion circuit. The output ends of the input capture circuit and the fifth analog-to-digital conversion circuit are connected to the control unit.

7. A signal conditioning method for an electromagnetic sensing device, characterized in that, The method is applied to the electromagnetic sensing device according to any one of claims 1 to 6, and the method includes: The excitation signal adjustment module adjusts the frequency and amplitude of the excitation signal according to the parameter value output by the second port, and outputs the adjusted excitation signal to the primary excitation coil, wherein the parameter value output by the second port is adjusted based on the parameter adjustment instruction received by the first port. The primary excitation coil generates an alternating magnetic field according to the adjusted excitation signal. The secondary induction coil generates an induction signal according to the alternating magnetic field. The induction signal conditioning module conditions the induction signal according to the parameter value output from the third port to obtain a liquid level signal for characterizing the liquid level to be detected, where the parameter value output from the third port is adjusted based on the parameter adjustment instruction received by the first port.

8. The method according to claim 7, wherein The control module encapsulates a control unit, a first digital-to-analog conversion circuit, and a first pulse modulation circuit. The control module also encapsulates a second digital-to-analog conversion circuit, a second pulse modulation circuit, a third pulse modulation circuit, a first analog-to-digital conversion circuit, and a second analog-to-digital conversion circuit. The induction signal conditioning module includes a first signal amplification circuit, a first operational amplifier circuit, a first band-pass filter circuit, a first switched-phase-sensitive detection circuit, a second switched-phase-sensitive detection circuit, a first low-pass filter circuit, a second low-pass filter circuit, a second operational amplifier circuit, and a third operational amplifier circuit. The method further includes: Obtain the signal output by the second analog-to-digital conversion circuit. Use the signal output by the second analog-to-digital conversion circuit as a first feedback signal to globally shift the phases of the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit relative to the phase of the pulse signal output by the first pulse modulation circuit, so that the first feedback signal has a voltage amplitude approaching zero, where the phase difference between the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit is always maintained at 90 degrees.

9. The method according to claim 8, wherein The device further includes a compensation induction coil disposed near the secondary induction coil. The control module also encapsulates a third digital-to-analog conversion circuit, a fourth pulse modulation circuit, a fifth pulse modulation circuit, a third analog-to-digital conversion circuit, and a fourth analog-to-digital conversion circuit. The induction signal conditioning module further includes a second signal amplification circuit, a fourth operational amplifier circuit, a second band-pass filter circuit, a third switched-phase-sensitive detection circuit, a fourth switched-phase-sensitive detection circuit, a third low-pass filter circuit, a fourth low-pass filter circuit, a fifth operational amplifier circuit, and a sixth operational amplifier circuit. The method further includes: Obtain the signal output by the fourth analog-to-digital conversion circuit. Use the signal output by the fourth analog-to-digital conversion circuit as a second feedback signal to globally shift the phases of the pulse signals output by the fourth pulse modulation circuit and the fifth pulse modulation circuit relative to the phase of the pulse signal output by the first pulse modulation circuit, so that the second feedback signal has a voltage amplitude approaching zero, where the phase difference between the pulse signals output by the fourth pulse modulation circuit and the fifth pulse modulation circuit is always maintained at 90 degrees.

10. The method according to claim 9, wherein The device further includes an interference signal detection module for obtaining the frequency and amplitude of the interference signal. The method further includes: The control unit obtains a first sampling signal obtained by the induction signal conditioning module conditioning the signal of the secondary induction coil and a second sampling signal obtained by the induction signal conditioning module conditioning the signal of the compensation induction coil, and performs zero adjustment and calibration on the first sampling signal and the second sampling signal to obtain a zero adjustment and calibration coefficient. Determine an interference correction value according to the amplitude of the interference signal, and determine a filtering coefficient corresponding to a preset digital notch filter in the control unit according to the frequency of the interference signal; Use the zero adjustment calibration coefficient, the interference correction value, and the filtering coefficient to perform signal processing on the first sampling signal and the second sampling signal to obtain the liquid level signal.

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