Electromagnetic sensing device and signal conditioning method therefor

Abstract

An electromagnetic sensing device, comprising 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 which are disposed near a liquid level to be detected. The control module (100) comprises 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). The excitation signal adjustment module (200) is connected to the primary excitation coil, and the excitation signal adjustment module (200) is used for adjusting the frequency and amplitude of an excitation signal on the basis of a parameter value outputted by the second port, and outputting the adjusted excitation signal to the primary excitation coil. The induction signal conditioning module (300) is connected to the secondary induction coil, and the induction signal conditioning module (300) is used for conditioning an induction signal on the basis of a parameter value outputted by the third port, so as to obtain a liquid level signal used for representing the liquid level to be detected. A signal conditioning method for an electromagnetic sensing device is further provided.

Description

Electromagnetic sensing device and signal conditioning method thereof

[0001] Reference of Related Applications

[0002] The present disclosure claims the entire benefit of the filing date of the application for an invention patent application with the State Intellectual Property Office of the People's Republic of China, filed on June 6, 2024, with the application number 202410731926.1, and the title of "Electromagnetic Sensing Device and Signal Conditioning Method Thereof", and incorporates by reference the entire content thereof.

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to the technical field of liquid level detection, and in particular to an electromagnetic sensing device and a signal conditioning method thereof.

[0005] BACKGROUND

[0006] In the process of high-quality continuous casting of steel billets, the liquid level height of the steel crystallizer is a very important control index. Liquid level fluctuation exceeding ±3mm not only seriously affects the quality of the steel billets, causing degradation of the quality, but also can cause forced shutdown, even a safety accident of leakage of molten steel, causing serious economic losses and personnel danger. Therefore, it is crucial to improve the accuracy of the detection results of the liquid level height of the steel crystallizer.

[0007] In the prior art, an electromagnetic sensor is usually used to detect the liquid level height. However, since the excitation signal frequency of the primary coil in the existing electromagnetic sensor is fixed, and the center frequency point of the band-pass filter module for filtering the induced signal of the secondary coil is also fixed, it is difficult to avoid electromagnetic interference generated by various devices (such as electromagnetic stirring, electromagnetic braking, etc.) in the field in actual application, resulting in low accuracy of the detection results of the liquid level height.

[0008] SUMMARY

[0009] The present disclosure provides an electromagnetic sensing device and a signal conditioning method thereof.

[0010] According to one aspect of the present disclosure, an electromagnetic sensing device is provided, which comprises a control module, an excitation signal adjustment module, an induced signal conditioning module, a human-computer interaction module, and a primary excitation coil and a secondary induced coil arranged near the liquid level to be detected.

[0011] The control module comprises a first port connected with the human-computer interaction module, a second port connected with the excitation signal adjustment module, and a third port connected with the induced signal conditioning module.

[0012] The excitation signal adjustment module is connected with the primary excitation coil, and 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;

[0013] The induction signal conditioning module is connected with 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 representing the liquid level to be detected.

[0014] 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.

[0015] In some embodiments, the control module is encapsulated with a control unit, a first digital-to-analog conversion circuit and a first pulse modulation circuit; the excitation signal adjustment module comprises a signal modulation circuit and a power amplification circuit;

[0016] The input end of the first digital-to-analog conversion circuit and the input end of the first pulse modulation circuit are connected with the control unit, the output end of the first digital-to-analog conversion circuit and the output end of the first pulse modulation circuit are connected with the input end of the signal modulation circuit as the second port, the output end of the signal modulation circuit is connected with the input end of the power amplification circuit, and the output end of the power amplification circuit is connected with the feedback end of the signal modulation circuit and the primary excitation coil respectively.

[0017] In some embodiments, the control module is further encapsulated with 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 comprises a first signal amplification circuit, a first operational amplification 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 amplification circuit and a third operational amplification circuit;

[0018] 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 connected with 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 are connected as the third port.

[0019] The output end of the second digital-analog conversion circuit is connected with the input end of the first operational amplifier circuit, and the output end of the first operational amplifier circuit is connected with the control end of the first band-pass filter circuit; the output end of the second pulse modulation circuit is connected with the control end of the first switch phase detector circuit, and the output end of the third pulse modulation circuit is connected with the control end of the second switch phase detector circuit;

[0020] The secondary induction coil is connected with the input end of the first signal amplification circuit, the output end of the first signal amplification circuit is connected with the input end of the first band-pass filter circuit, the output end of the first band-pass filter circuit is connected with the input end of the first switch phase detector circuit and the input end of the second switch phase detector circuit respectively, the output end of the first switch phase detector circuit is connected with the input end of the first low-pass filter circuit, the output end of the first low-pass filter circuit is connected with the input end of the second operational amplifier circuit, and the output end of the second operational amplifier circuit is connected with the input end of the first analog-digital conversion circuit; the output end of the second switch phase detector circuit is connected with the input end of the second low-pass filter circuit, the output end of the second low-pass filter circuit is connected with the input end of the third operational amplifier circuit, and the output end of the third operational amplifier circuit is connected with the input end of the second analog-digital conversion circuit.

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

[0022] In some embodiments, the device further comprises a compensation induction coil arranged near the secondary induction coil; the control module further encapsulates a third digital-analog conversion circuit, a fourth pulse modulation circuit, a fifth pulse modulation circuit, a third analog-digital conversion circuit and a fourth analog-digital conversion circuit; the induction signal conditioning module further comprises a second signal amplification circuit, a fourth operational amplifier circuit, a second band-pass filter circuit, a third switch phase detector circuit, a fourth switch phase detector circuit, a third low-pass filter circuit, a fourth low-pass filter circuit, a fifth operational amplifier circuit and a sixth operational amplifier circuit;

[0023] The input end of the third digital-analog conversion circuit, the input end of the fourth pulse modulation circuit, the input end of the fifth pulse modulation circuit, the output end of the third analog-digital conversion circuit and the output end of the fourth analog-digital conversion circuit are connected with the control unit, and the output end of the third digital-analog conversion circuit, the output end of the fourth pulse modulation circuit and the output end of the fifth pulse modulation circuit are the third port;

[0024] The output end of the third digital-to-analog conversion circuit is connected with the input end of the fourth operational amplifier circuit, and the output end of the fourth operational amplifier circuit is connected with the control end of the second band-pass filter circuit; the output end of the fourth pulse modulation circuit is connected with the control end of the third switch phase detector circuit, and the output end of the fifth pulse modulation circuit is connected with the control end of the fourth switch phase detector circuit;

[0025] The compensation induction coil is connected with the input end of the second signal amplification circuit, the output end of the second signal amplification circuit is connected with the input end of the second band-pass filter circuit, the output end of the second band-pass filter circuit is connected with the input end of the third switch phase detector circuit and the input end of the fourth switch phase detector circuit respectively, the output end of the third switch phase detector circuit is connected with the input end of the third low-pass filter circuit, the output end of the third low-pass filter circuit is connected with the input end of the fifth operational amplifier circuit, the output end of the fifth operational amplifier circuit is connected with the input end of the third analog-to-digital conversion circuit; the output end of the fourth switch phase detector circuit is connected with the input end of the fourth low-pass filter circuit, the output end of the fourth low-pass filter circuit is connected with the input end of the sixth operational amplifier circuit, and the output end of the sixth operational amplifier circuit is connected with the input end of the fourth analog-to-digital conversion circuit.

[0026] In some embodiments, 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 signal output by the fourth pulse modulation circuit and the fifth pulse modulation circuit.

[0027] In some embodiments, the device further comprises an interference signal detection module, and the control module further comprises a fourth port connected with the interference signal detection module.

[0028] The interference signal detection module is configured to acquire 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.

[0029] In some embodiments, the interference signal detection module comprises a current mutual inductance circuit, a seventh operational amplifier circuit, a filter circuit, a comparison circuit and a detector circuit; and the induction signal conditioning module further comprises an input capture circuit and a fifth analog-to-digital conversion circuit.

[0030] The output end of the current mutual inductance circuit is connected with the input end of the seventh operational amplifier circuit, the output end of the seventh operational amplifier circuit is connected with the input end of the filter circuit, the output end of the filter circuit is connected with the input end of the comparison circuit and the input end of the detection circuit respectively, the output end of the comparison circuit is connected with the input end of the input capture circuit, the output end of the detection circuit is connected with the input end of the fifth analog-digital conversion circuit, and the output end of the input capture circuit and the output end of the fifth analog-digital conversion circuit are connected with the control unit.

[0031] According to another aspect of the present disclosure, a signal conditioning method of an electromagnetic sensing device is provided, the method is applied to the electromagnetic sensing device, and the method comprises:

[0032] 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 obtained by adjusting based on the parameter adjustment instruction received by the first port;

[0033] The primary excitation coil generates an alternating magnetic field according to the adjusted excitation signal;

[0034] The secondary induction coil generates an induction signal according to the alternating magnetic field;

[0035] The induction signal conditioning module conditions the induction information according to the parameter value output by the third port to obtain a liquid level signal used for representing the liquid level to be detected, wherein the parameter value output by the third port is obtained by adjusting based on the parameter adjustment instruction received by the first port.

[0036] In some embodiments, the control module further encapsulates a second digital-analog conversion circuit, a second pulse modulation circuit, a third pulse modulation circuit, a first analog-digital conversion circuit and a second analog-digital conversion circuit; the induction signal conditioning module comprises a first signal amplification circuit, a first operational amplifier circuit, a first band-pass filter circuit, a first switched phase detection circuit, a second switched phase 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; and the method further comprises:

[0037] obtaining the signal output by the second analog-digital conversion circuit;

[0038] The signal output by the second analog-digital conversion circuit is taken as a first feedback signal, and the phases of the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit are moved relative to the phase of the pulse signal output by the first pulse modulation circuit as a whole to make the first feedback signal have a voltage amplitude close to zero, wherein 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.

[0039] In some embodiments, the device further comprises a compensation induction coil arranged near the secondary induction coil; the control module further encapsulates a third digital-analog conversion circuit, a fourth pulse modulation circuit, a fifth pulse modulation circuit, a third analog-digital conversion circuit and a fourth analog-digital conversion circuit; the induction signal conditioning module further comprises a second signal amplification circuit, a fourth operational amplifier circuit, a second band-pass filter circuit, a third switched phase detection circuit, a fourth switched phase 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 comprises:

[0040] obtaining the signal output by the fourth analog-digital conversion circuit;

[0041] The signal output by the fourth analog-digital conversion circuit is taken as a second feedback signal, and the phases of the pulse signals output by the third pulse modulation circuit and the fourth pulse modulation circuit are moved relative to the phase of the pulse signal output by the first pulse modulation circuit as a whole to make the second feedback signal have a voltage amplitude close to 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.

[0042] In some embodiments, the method further comprises:

[0043] The control unit obtains a first sampling signal obtained by the induction signal conditioning module after signal conditioning of the secondary induction coil and a second sampling signal obtained by the induction signal conditioning module after signal conditioning of the compensation induction coil, and performs zero calibration on the first sampling signal and the second sampling signal to obtain a zero calibration coefficient;

[0044] According to the amplitude of the interference signal, an interference correction value is determined, and according to the frequency of the interference signal, a filter coefficient corresponding to a digital notch filter preset in the control unit is determined;

[0045] The first sampling signal and the second sampling signal are processed by using the zero calibration coefficient, the interference correction value and the filter coefficient to obtain the liquid level signal.

[0046] In some embodiments, the parameter value output by the second port and the parameter value output by the third port can be adjusted by parameter adjustment instructions 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 sensing information, effectively avoid electromagnetic interference generated by various devices on site, and make the detection result of the liquid level to be detected more accurate.

[0047] BRIEF DESCRIPTION OF DRAWINGS

[0048] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the accompanying drawings required to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0050] One or more embodiments are exemplarily illustrated by pictures in the drawings corresponding to the embodiments, and the exemplarily illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, unless otherwise specified. The drawings in the drawings do not constitute a proportional limitation.

[0051] FIG. 1 is a structural schematic diagram of an electromagnetic sensing device provided by an embodiment of the present disclosure;

[0052] FIG. 2 is a structural schematic diagram of an electromagnetic sensing device provided by the related art;

[0053] FIG. 3 is a structural schematic diagram of another electromagnetic sensing device provided by an embodiment of the present disclosure;

[0054] FIG. 4 is a structural schematic diagram of still another electromagnetic sensing device provided by an embodiment of the present disclosure;

[0055] FIG. 5 is a structural schematic diagram of yet another electromagnetic sensing device provided by an embodiment of the present disclosure;

[0056] FIG. 6 is a flow schematic diagram of a signal conditioning method of an electromagnetic sensing device provided by an embodiment of the present disclosure.

[0057] DETAILED DESCRIPTION

[0058] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0059] The following disclosure provides numerous different embodiments or examples for implementing various structures of this disclosure. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this disclosure. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0060] To address the issue of low accuracy in liquid level detection by existing electromagnetic sensors, this disclosure provides an electromagnetic sensing device and its signal conditioning method, which can effectively avoid electromagnetic interference generated by various on-site devices, thereby making the detection results of the liquid level to be detected more accurate.

[0061] Referring to Figure 1, Figure 1 is a structural schematic diagram of an electromagnetic sensing device provided in an embodiment of this disclosure. As shown in Figure 1, 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;

[0062] 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.

[0063] The excitation signal adjustment module 200 is connected to the primary excitation coil. The excitation signal adjustment module 200 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.

[0064] The induction signal conditioning module 300 is connected to the secondary induction coil, which is used to generate an induction signal based on the alternating magnetic field. The induction signal conditioning module 300 is used to condition the induction information based on the parameter value output from the third port to obtain a liquid level signal that characterizes the liquid level to be detected.

[0065] 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.

[0066] It should be noted that the control module 100 can further include other circuits such as an analog-to-digital conversion circuit, a digital-to-analog conversion circuit, a pulse modulation circuit, etc. in addition to the central processing unit (CPU). The input and output ports of these circuits correspond to different pins of the chip.

[0067] The arrangement direction, shape, and number of turns of the primary excitation coil and the 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 ring coils or rectangular coils, etc. As an optional embodiment, 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 arranged in parallel to the liquid level to be detected, and the central axis of the secondary induction coil can be arranged perpendicular to the plane of the liquid level to be detected. In this way, the amplitude of the induced electric field on the secondary induction coil can be more sensitive to changes in the liquid level.

[0068] The excitation signal adjustment module 200 can adjust the frequency and amplitude of the excitation signal (i.e., the alternating current) according to the parameter value output by 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 can generate an alternating induced electric field in the alternating magnetic field. The alternating induced electric field can further generate eddy current (i.e., the induced signal) in the closed loop to the induced signal conditioning module 300. At this time, the induced signal conditioning module 300 can condition the induced information according to the parameter value output by the third port to obtain a liquid level signal for representing the liquid level to be detected.

[0069] In related technologies, the amplitude of the excitation signal is usually obtained by dividing a fixed voltage source using a potentiometer, and the frequency of the excitation signal is usually obtained by dividing a fixed active crystal oscillator using a frequency division module. Therefore, the amplitude and frequency of the modulated excitation signal are usually fixed and cannot be adjusted. When filtering the induced information, a filter circuit with a fixed center frequency is usually used, and when amplitude modulation or phase modulation is performed on the induced information, a potentiometer is usually used for adjustment, as shown in FIG. 2. Since the amplitude, frequency, and center frequency of the filter circuit of the excitation signal are fixed and cannot be adjusted online, and the potentiometer has a large temperature coefficient, the detection result can easily drift. Therefore, the detection result of the existing electromagnetic sensor is not accurate enough.

[0070] In the embodiment of the present disclosure, the inductive signal does not need to be adjusted by using a potentiometer, and the parameter adjustment instruction input by the man-machine interaction module 400 can be used to adjust the parameter value output by the second port and the parameter value output by the third port, so as to flexibly adjust the frequency and amplitude of the excitation signal and the parameters required in the conditioning process of the inductive signal, thereby effectively avoiding electromagnetic interference generated by various devices on site, and making the detection result of the liquid level to be detected more accurate.

[0071] Further, referring to FIG. 3, the control module 100 is encapsulated with a control unit CPU, a first digital-to-analog conversion circuit DAC1 and a first pulse modulation circuit PWM1; the excitation signal adjustment module 200 includes a signal modulation circuit 201 and a power amplification circuit 202;

[0072] The input end of the first digital-to-analog conversion circuit DAC1 and the input end of the first pulse modulation circuit PWM1 are connected with the control unit CPU, the output end of the first digital-to-analog conversion circuit DAC1 and the output end of the first pulse modulation circuit PWM1 are connected with the input end of the signal modulation circuit 201 as the second port, the output end of the signal modulation circuit 201 is connected with the input end of the power amplification circuit 202, and the output end of the power amplification circuit 202 is connected with the feedback end of the signal modulation circuit 201 and the primary excitation coil respectively.

[0073] Specifically, the first digital-to-analog conversion circuit DAC1 can adjust the voltage amplitude of the signal output according to the voltage amplitude parameter set by the user, so as to realize amplitude modulation of the signal in the modulation circuit. The first pulse modulation circuit PWM1 microcontroller can adjust the frequency of the pulse signal output according to the frequency parameter set by the user, so as to realize frequency modulation of the signal in the modulation circuit. Then, after the modulation circuit modulation and the power amplification circuit 202 amplification, an excitation signal with adjustable amplitude and frequency close to a sine wave can be obtained to the primary excitation coil, so that the primary excitation coil can generate an alternating magnetic field according to the excitation signal.

[0074] Further, continuing to refer to FIG. 3, the control module 100 is further encapsulated with a second digital-to-analog conversion circuit DAC2, a second pulse modulation circuit PWM2, a third pulse modulation circuit PWM3, a first analog-to-digital conversion circuit ADC1 and a second analog-to-digital conversion circuit ADC2; the inductive signal conditioning module 300 includes a first signal amplification circuit 301, a first operational amplification circuit 302, a first band-pass filter circuit 303, a first switched phase-sensitive detection circuit 304, a second switched phase-sensitive detection circuit 305, a first low-pass filter circuit 306, a second low-pass filter circuit 307, a second operational amplification circuit 308 and a third operational amplification circuit 309;

[0075] The input end of the second digital-to-analog conversion circuit DAC2, the input end of the second pulse modulation circuit PWM2, the input end of the third pulse 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 connected with the control unit CPU, and the output end of the second digital-to-analog conversion circuit DAC2, the output end of the second pulse modulation circuit PWM2 and the output end of the third pulse modulation circuit PWM3 are all third ports;

[0076] The output end of the second digital-to-analog conversion circuit DAC2 is connected with the input end of the first operational amplifier circuit 302, and the output end of the first operational amplifier circuit 302 is connected with the control end of the first band-pass filter circuit 303; the output end of the second pulse modulation circuit PWM2 is connected with the control end of the first switch phase detection circuit 304, and the output end of the third pulse modulation circuit PWM3 is connected with the control end of the second switch phase detection circuit 305;

[0077] The secondary induction coil is connected with the input end of the first signal amplification circuit 301, the output end of the first signal amplification circuit 301 is connected with the input end of the first band-pass filter circuit 303, and the output end of the first band-pass filter circuit 303 is connected with the input end of the first switch phase detection circuit 304 and the input end of the second switch phase detection circuit 305 respectively, the output end of the first switch phase detection circuit 304 is connected with the input end of the first low-pass filter circuit 306, the output end of the first low-pass filter circuit 306 is connected with the input end of the second operational amplifier circuit 308, and the output end of the second operational amplifier circuit 308 is connected with the input end of the first analog-to-digital conversion circuit ADC1; the output end of the second switch phase detection circuit 305 is connected with the input end of the second low-pass filter circuit 307, the output end of the second low-pass filter circuit 307 is connected with the input end of the third operational amplifier circuit 309, and the output end of the third operational amplifier circuit 309 is connected with the input end of the second analog-to-digital conversion circuit ADC2.

[0078] Specifically, the second digital-to-analog conversion circuit DAC2 can adjust the voltage amplitude of the signal output according to the voltage amplitude parameter set by the user, and the signal after the voltage amplitude adjustment is input to the first band-pass filter circuit 303 for voltage-controlled tracking after being amplified by the first operational amplifier circuit 302, 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.

[0079] The second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3 are respectively used to output pulse signals to the respective switch phase detection circuits, and the frequency of the pulse signals can be varied according to the frequency parameter received by the first port of the control module 100, and the frequency is increased or decreased by a preset step, 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 frequency of the pulse signals output by the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3 needs to be equal to the frequency of the pulse signals output by the first pulse modulation circuit PWM1, that is, equal to the center frequency of the first band-pass filter circuit 303. In addition, the phase difference between the pulse signals output by the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3 (i.e., the A phase 0° and the A phase 90° in FIG. 3) 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 induced signal input to the first switch phase detection circuit 304, that is, the phase difference is 0°, and the phase of the pulse signal output by the second pulse modulation circuit PWM2 is orthogonal to the induced signal input to the first switch phase detection circuit 304, that is, the phase difference is 90°. However, due to interference signal interference and self-drift, the phase of the pulse signal output by the second pulse modulation circuit PWM2 often deviates from the phase of the induced signal input to the first switch phase detection circuit 304, and the phase of the pulse signal output by the second pulse modulation circuit PWM2 also deviates from the phase of the induced signal input to the first switch phase detection circuit 304. At this time, the signal close to direct current obtained by the second analog-to-digital conversion circuit ADC2 after low-pass filtering can be used as a feedback signal (when the feedback signal is close to 0, it indicates that the phase of the pulse signal output by the third pulse modulation circuit PWM3 is orthogonal to the phase of the detected signal, and when the feedback signal is positive or negative, the phase of the pulse signal output by the third pulse modulation circuit PWM3 leads or lags the phase of the detected signal), and the control unit CPU can control the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3 to move the phase of the pulse signal output by the first pulse modulation circuit PWM1 which keeps 90° phase angle and is overall unchanged relative to the frequency phase, so that proportional-integral-derivative (PID) closed-loop regulation can be performed. In general, the feedback signal close to 0 is taken as the closed-loop control target.

[0080] In this way, the phase difference between the input pulse signal and the input induced signal in the first switch phase detection circuit 304 and the phase difference between the input pulse signal and the input induced signal in the second switch phase detection circuit 305 can be closed-loop controlled and locked, and after the phase changes due to electromagnetic interference in the front end, real-time automatic correction can be realized, the deviation of the final output liquid level signal is reduced, and the anti-interference ability of the electromagnetic sensing device is increased.

[0081] Further, 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 frequency of the pulse signals output by the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3.

[0082] Specifically, the second digital-to-analog conversion circuit DAC2 can adjust the voltage amplitude of the signal output by the second digital-to-analog conversion circuit DAC2 according to the voltage amplitude parameter set by the user, and the signal after voltage amplitude adjustment is input to the first band-pass filter circuit 303 for voltage-controlled tracking after being amplified by the first operational amplifier circuit 302, thereby changing the filtering center frequency of the first band-pass filter circuit 303, and making 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 signal in the induced signal, and improve the accuracy of the detection result of the electromagnetic sensing device.

[0083] Further, the control unit CPU is configured to move the phase 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 as a whole, so that the first feedback signal is a voltage amplitude close to zero, and the phase difference between the pulse signals output by the second pulse modulation circuit PWM2 and the third pulse modulation circuit PWM3 is always maintained at 90 degrees.

[0084] Specifically, after receiving the signal output by the second analog-digital conversion circuit ADC2, the control unit CPU can move the phase 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 as a whole to make the first feedback signal have a voltage amplitude close to zero. In this way, the phase difference between the input pulse signal and the input induced signal in the first switched-phase detection circuit 304 and the phase difference between the input pulse signal and the input induced signal in the second switched-phase detection circuit 305 can be locked in a closed loop, and the phase can be automatically corrected in real time when the front end is subjected to electromagnetic interference and the phase changes, thereby reducing the deviation of the final output liquid level signal and increasing the anti-interference ability of the electromagnetic sensing device.

[0085] Further, continuing to refer to FIG. 3, the device further includes a compensation induction coil arranged near the secondary induction coil; the control module 100 further encapsulates a third digital-analog conversion circuit DAC3, a fourth pulse modulation circuit PWM4, a fifth pulse modulation circuit PWM5, a third analog-digital conversion circuit ADC3, and a fourth analog-digital conversion circuit ADC4; the induced signal conditioning module 300 further includes a second signal amplification circuit 310, a fourth operational amplification circuit 311, a second band-pass filter circuit 312, a third switched-phase detection circuit 313, a fourth switched-phase detection circuit 314, a third low-pass filter circuit 315, a fourth low-pass filter circuit 316, a fifth operational amplification circuit 317, and a sixth operational amplification circuit 318.

[0086] The input end of the third digital-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-digital conversion circuit ADC3, and the output end of the fourth analog-digital conversion circuit ADC4 are connected with the control unit CPU, and the output end of the third digital-analog conversion circuit DAC3, the output end of the fourth pulse modulation circuit PWM4, and the output end of the fifth pulse modulation circuit PWM5 are all third ports.

[0087] The output end of the third digital-analog conversion circuit DAC3 is connected with the input end of the fourth operational amplification circuit 311, and the output end of the fourth operational amplification circuit 311 is connected with the control end of the second band-pass filter circuit 312; the output end of the fourth pulse modulation circuit PWM4 is connected with the control end of the third switched-phase detection circuit 313, and the output end of the fifth pulse modulation circuit PWM5 is connected with the control end of the fourth switched-phase detection circuit 314.

[0088] The compensation inductive coil is connected with the input end of the second signal amplification circuit 310, the output end of the second signal amplification circuit 310 is connected with 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 with the input end of the third switch phase detection circuit 313 and the input end of the fourth switch phase detection circuit 314, the output end of the third switch phase detection circuit 313 is connected with the input end of the third low-pass filter circuit 315, the output end of the third low-pass filter circuit 315 is connected with the input end of the fifth operational amplifier circuit 317, the output end of the fifth operational amplifier circuit 317 is connected with the input end of the third analog-to-digital conversion circuit ADC3; the output end of the fourth switch phase detection circuit 314 is connected with the input end of the fourth low-pass filter circuit 316, the output end of the fourth low-pass filter circuit 316 is connected with the input end of the sixth operational amplifier circuit 318, the output end of the sixth operational amplifier circuit 318 is connected with the input end of the fourth analog-to-digital conversion circuit ADC4.

[0089] Specifically, the third digital-to-analog conversion circuit DAC3 can adjust the voltage amplitude of the signal output according to the voltage amplitude parameter set by the user, and the signal after voltage amplitude adjustment is input to the second band-pass filter circuit 312 for voltage control tracking after being amplified by the fourth operational amplifier circuit 311, 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.

[0090] The fourth pulse modulation circuit PWM4 and the fifth pulse modulation circuit PWM5 are respectively used to output pulse signals to the respective switch phase-sensitive detection circuits. The frequency of the pulse signals can be varied according to the frequency parameter received by the first port of the control module 100, and the frequency is increased or decreased by a preset step, so as to adjust the frequency 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 frequency of the pulse signals output by the fourth pulse modulation circuit PWM4 and the fifth pulse modulation circuit PWM5 needs to be equal to the frequency of the pulse signals output by the first pulse modulation circuit PWM1, i.e., equal to the center frequency of the second band-pass filter circuit 312. In addition, the phase difference between the pulse signals output by the fourth pulse modulation circuit PWM4 and the fifth pulse modulation circuit PWM5 (i.e., the B phase 0° and the B phase 90° in FIG. 3) is 90°. 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 detection circuit 313, i.e., the phase difference is 0°, and 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 detection circuit 314, i.e., the phase difference is 90°. However, due to interference signal interference and self-drift, the phase of the pulse signal output by the fourth pulse modulation circuit PWM4 often has a phase deviation from the induced signal input to the third switch phase-sensitive detection circuit 313, and the phase of the pulse signal output by the fifth pulse modulation circuit PWM5 also has a phase deviation from the induced signal input to the fourth switch phase-sensitive detection circuit 314. At this time, the signal close to direct current obtained by low-pass filtering after phase-sensitive detection can be collected by the fourth analog-to-digital conversion circuit ADC4 as a feedback signal (when the feedback signal is close to 0, it indicates that the phase of the pulse signal output by the fifth pulse modulation circuit PWM5 is orthogonal to the phase of the detected signal, and when the feedback signal is a positive or negative value, the phase of the pulse signal output by the fifth pulse modulation circuit PWM5 leads or lags the phase of the detected signal), and the control unit CPU can control the phase of the pulse signal output by the first pulse modulation circuit PWM1 to move according to the size of the feedback information, so that the pulse signal output by the fourth pulse modulation circuit PWM4 and the fifth pulse modulation circuit PWM5 remains 90° phase angle and the overall frequency phase does not change. In this way, proportional-integral-derivative (PID) closed-loop regulation can be performed, and in general, the feedback signal close to 0 is taken as the closed-loop control target.

[0091] In this way, the phase difference between the input pulse signal and the input induced signal in the third switch phase detection circuit 313 and the phase difference between the input pulse signal and the input induced signal in the fourth switch phase detection circuit 314 can be closed-loop controlled and locked, and after the phase changes due to electromagnetic interference in the front end, real-time automatic correction can be realized, the deviation of the final output liquid level signal is reduced, and the anti-interference ability of the electromagnetic sensing device is increased.

[0092] 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 frequency of the pulse signals output by the fourth pulse modulation circuit PWM4 and the fifth pulse modulation circuit PWM5.

[0093] Specifically, the third digital-to-analog conversion circuit DAC3 can adjust the voltage amplitude of the signal output by the third digital-to-analog conversion circuit DAC3 according to the voltage amplitude parameter set by the user, and the signal after voltage amplitude adjustment is input to the second band-pass filter circuit 312 for voltage-controlled tracking after being amplified by the fourth operational amplifier circuit 311, thereby changing the filtering 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. In this way, the second band-pass filter circuit 312 can effectively filter out the interference signal in the induced signal, and improve the accuracy of the detection result of the electromagnetic sensing device.

[0094] Further, the control unit CPU is configured to use the signal output by the fourth analog-to-digital conversion circuit ADC4 as a second feedback signal, and move the phase 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 as a whole, so that the voltage amplitude of the second feedback signal tends to zero, and the phase difference between the pulse signals output by the third pulse modulation circuit PWM3 and the fourth pulse modulation circuit PWM4 is always maintained at 90 degrees.

[0095] Specifically, after receiving the signal output by the fourth analog-to-digital conversion circuit ADC4, the control unit CPU can move 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 as a whole to make the second feedback signal approach zero in voltage amplitude. In this way, the phase difference between the input pulse signal and the input induced signal in the third switched phase-sensitive detection circuit 313 and the phase difference between the input pulse signal and the input induced signal in the fourth switched phase-sensitive detection circuit 314 can be controlled and locked in a closed loop, and after the front end is subjected to electromagnetic interference and the phase changes, real-time automatic correction can be realized, the deviation of the finally output liquid level signal can be reduced, and the anti-interference ability of the electromagnetic sensing device can be increased.

[0096] Further, referring to FIG. 4, the device further comprises an interference signal detection module 500, and the control module 100 further comprises a fourth port connected with the interference signal detection module 500.

[0097] The interference signal detection module 500 is configured to acquire 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.

[0098] In an embodiment, the interference signal detection module 500 can also be used to acquire the frequency and amplitude of the interference signal, and according to the acquired frequency and amplitude of the interference signal, the interference correction value and the filter coefficient corresponding to the digital notch filter can be calculated, so that the deviation and fluctuation of the liquid level signal can be reduced according to the interference correction value and the filter coefficient corresponding to the digital notch filter in the subsequent process, thereby increasing the anti-interference ability of the electromagnetic sensing device.

[0099] Further, referring to FIG. 5, the interference signal detection module 500 comprises a current mutual inductance circuit 501, a seventh operational amplifier circuit 502, a filter circuit 503, a comparison circuit 504 and a detection circuit 505; and the induced signal conditioning module 300 further comprises an input capture circuit IC1 and a fifth analog-to-digital conversion circuit ADC5.

[0100] The output end of the current mutual inductance circuit 501 is connected with the input end of the seventh operational amplifier circuit 502, the output end of the seventh operational amplifier circuit 502 is connected with the input end of the filter circuit 503, the output end of the filter circuit 503 is connected with the input end of the comparison circuit 504 and the input end of the detection circuit 505 respectively, the output end of the comparison circuit 504 is connected with the input end of the input capture circuit IC1, the output end of the detection circuit 505 is connected with the input end of the fifth analog-to-digital conversion circuit ADC5, and the output end of the input capture circuit IC1 and the output end of the fifth analog-to-digital conversion circuit ADC5 are connected with the control unit CPU.

[0101] In an embodiment, the current mutual inductance circuit 501 can also be used to detect the current mutual inductance signal output by an external electromagnetic interference generating device, and then the signal is amplified by the seventh operational amplifier circuit 502 and filtered by the filter circuit 503, and then input into the input capture circuit IC1 through the comparison circuit 504, the frequency of the interference signal is obtained through the input capture circuit IC1, and the signal is input into the fifth analog-to-digital conversion circuit ADC5 through the detection circuit 505, and the amplitude of the interference signal is obtained through the fifth analog-to-digital conversion circuit ADC5. According to the obtained frequency and amplitude of the interference signal, the electromagnetic sensing device can better adjust to avoid interference or add interference correction value to the final liquid level calculation to correct the error, or select a reasonable digital notch filter filtering coefficient in the control unit CPU to better filter out the interference of the final liquid level result, and also maintain good response speed.

[0102] It should be noted that the input capture circuit IC1 can be set to capture the pulse width, and the pulse width is recorded by the count value of the connected timer. The number of pulses in a period of time can be obtained through the count value, so as to determine the frequency of the interference signal. The fifth analog-to-digital conversion circuit ADC5 can sample the processed current mutual inductance signal to obtain the alternating current effective value or peak voltage, and then multiply the measured alternating current effective value or peak voltage by a proportional value to obtain the actual alternating current effective value or peak voltage of the measured device (i.e. the electromagnetic interference generating device) (i.e. the amplitude of the interference signal).

[0103] Referring to FIG. 6, FIG. 6 is a flowchart of a signal conditioning method of an electromagnetic sensing device according to an embodiment of the present disclosure. As shown in FIG. 6, the signal conditioning method of the electromagnetic sensing device is applied to the electromagnetic sensing device described above, and the method comprises:

[0104] In step 601, 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.

[0105] In step 602, the primary excitation coil generates an alternating magnetic field according to the adjusted excitation signal.

[0106] In step 603, the secondary induction coil generates an induction signal according to the alternating magnetic field.

[0107] In step 604, the induction signal conditioning module conditions the induction information according to the parameter value output by the third port to obtain a liquid level signal for representing the liquid level to be detected, wherein the parameter value output by the third port is adjusted based on the parameter adjustment instruction received by the first port.

[0108] In the related art, the amplitude of the excitation signal is usually obtained by dividing a fixed voltage source using a potentiometer, and the frequency of the excitation signal is usually obtained by dividing a fixed active crystal oscillator using a frequency division module, so that the amplitude and frequency of the excitation signal obtained by modulation are usually fixed and cannot be adjusted. When filtering the induced information, a filter circuit with a fixed center frequency is usually used for filtering, and when amplitude modulation or phase modulation is performed on the induced information, a potentiometer is usually used for adjustment, as shown in FIG. 2. Since the amplitude, frequency of the excitation signal, and the center frequency of the filter circuit are fixed and cannot be adjusted online, and the potentiometer has a large temperature coefficient, the detection result is prone to drift, so that the detection result of the existing electromagnetic sensor is not accurate enough.

[0109] In the embodiments of the present disclosure, the induced signal does not need to be adjusted using a potentiometer, and the parameter adjustment instruction input by the man-machine interaction module can be used to adjust the parameter value output by the second port and the parameter value output by the third port, so as to flexibly adjust the frequency and amplitude of the excitation signal and the parameters required in the conditioning process of the induced information, thereby effectively avoiding electromagnetic interference generated by various devices on site, and making the detection result of the liquid level to be detected more accurate.

[0110] Further, as shown in FIG. 3, the control module further 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 induced 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 detection circuit, a second switched phase-sensitive detection circuit, a first low-pass filter circuit, a second low-pass filter circuit, a second operational amplification circuit, and a third operational amplification circuit; and the method further includes:

[0111] obtaining a signal output by the second analog-to-digital conversion circuit;

[0112] The signal output by the second analog-to-digital conversion circuit is used as a first feedback signal to move 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 as a whole, so that the first feedback signal has a voltage amplitude close to zero, wherein 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.

[0113] In an embodiment, after receiving the signal output by the second analog-digital conversion circuit, the control unit can move 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 as a whole to make the first feedback signal have a voltage amplitude close to zero. In this way, the phase difference between the input pulse signal and the input induced signal in the first switched-phase detection circuit and the phase difference between the input pulse signal and the input induced signal in the second switched-phase detection circuit can be locked by closed-loop control, and the deviation of the final output liquid level signal can be reduced and the anti-interference ability of the electromagnetic sensing device can be increased when the front end is subjected to electromagnetic interference and the phase changes.

[0114] Further, the electromagnetic sensing device further comprises a compensation induction coil arranged near the secondary induction coil; the control module further encapsulates a third digital-analog conversion circuit, a fourth pulse modulation circuit, a fifth pulse modulation circuit, a third analog-digital conversion circuit and a fourth analog-digital conversion circuit; the induced signal conditioning module further comprises a second signal amplification circuit, a fourth operational amplifier circuit, a second band-pass filter circuit, a third switched-phase detection circuit, a fourth switched-phase 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 comprises:

[0115] obtaining a signal output by the fourth analog-digital conversion circuit;

[0116] taking the signal output by the fourth analog-digital conversion circuit as a second feedback signal, and moving 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 as a whole to make the second feedback signal have a voltage amplitude close to 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.

[0117] In an embodiment, after receiving the signal output by the fourth analog-digital conversion circuit, the control unit can move 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 as a whole to make the second feedback signal have a voltage amplitude close to zero. In this way, the phase difference between the input pulse signal and the input induced signal in the third switched-phase detection circuit and the phase difference between the input pulse signal and the input induced signal in the fourth switched-phase detection circuit can be locked by closed-loop control, and the deviation of the final output liquid level signal can be reduced and the anti-interference ability of the electromagnetic sensing device can be increased when the front end is subjected to electromagnetic interference and the phase changes.

[0118] Further, the method further comprises:

[0119] The control unit obtains a first sampling signal obtained after the induction signal conditioning module performs signal conditioning on the secondary induction coil and a second sampling signal obtained after the induction signal conditioning module performs signal conditioning on the compensation induction coil, and performs zero calibration on the first sampling signal and the second sampling signal to obtain a zero calibration coefficient;

[0120] The interference correction value is determined according to the amplitude of the interference signal, and the filter coefficient corresponding to the digital notch filter preset in the control unit is determined according to the frequency of the interference signal;

[0121] The first sampling signal and the second sampling signal are processed by using the zero calibration coefficient, the interference correction value, and the filter coefficient to obtain a liquid level signal.

[0122] Specifically, before using the electromagnetic sensing device to detect the liquid level, the electromagnetic sensing device can be zero calibrated, that is, the first sampling signal and the second sampling signal satisfy the following relationship: Vs-KxVc=0.

[0123] Wherein, Vs represents the first sampling signal, Vc represents the second sampling signal, and K is the zero calibration coefficient. Compared with the zero calibration in the superposition amplification module in FIG. 2 (that is, the induction signal of the compensation induction coil is used as a signal source, and two amplitude and phase modulated alternating currents are obtained by adjusting two potentiometers, and then the two amplitude and phase modulated alternating currents are superimposed and offset with the induction signal of the secondary induction coil to achieve zero calibration), the zero calibration in the present disclosure can reduce the interference signal mixed in, thereby improving the detection signal-to-noise ratio and the stability of the electromagnetic sensing device.

[0124] 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 is subjected to 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 is subjected to 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 calibration coefficient K can be calculated by using the above formula.

[0125] In the process of liquid level detection using the electromagnetic sensor device, the frequency and amplitude of the interference signal can be obtained by the interference signal detection module, and then the interference correction value is determined according to the amplitude of the interference signal, and the filter coefficient corresponding to the digital notch filter preset in the control unit is determined according to the frequency of the interference signal. Specifically, the interference correction value can be determined by the following formula: C=a×Co+b;

[0126] Wherein, a and b are parameters, which are obtained by fitting experimental data, and Co is the AC effective value or peak voltage detected by the fifth analog-to-digital conversion circuit in the case of external current transformer signal input, or a parameter in the control unit that can be manually adjusted in the case of no external current transformer signal input.

[0127] Since the actual electromagnetic interference of the electromagnetic sensor device will not only cause a direct current error value, but also have AC fluctuation interference, the digital notch filter can effectively filter out the AC interference loaded on the output liquid level corresponding direct current signal, without affecting the direct current component and response speed. The digital notch filter here can be a filter equation in the control unit, and the filter coefficients of the filter equation are calculated by matlab in advance 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 by the input capture circuit, and then loads the filter coefficients corresponding to the digital notch filter from the memory of the control module.

[0128] Finally, the control unit can use the zero adjustment calibration coefficient and the interference correction value to process the first sampling signal and the second sampling signal, and the processing process is: Vs-K×Vc+K×C. Then the processed signal is filtered by the digital notch filter to output the liquid level signal.

[0129] In the embodiment, the electromagnetic sensor 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 induced signal according to the actual electromagnetic interference of the application site, effectively avoid the interference caused by the electromagnetic stirring, electromagnetic braking and other equipment in the application site of the liquid level meter to the electromagnetic sensor device, thereby improving the signal-to-noise ratio and anti-interference ability of the electromagnetic sensor device. Moreover, the phase difference between the carrier of the switch phase-sensitive detection circuit in the electromagnetic sensor device and the input induced signal realizes closed-loop control locking, which can be automatically corrected in real time after the front end is subjected to electromagnetic interference and the phase changes, reduces the deviation of the final output liquid level signal, and increases the anti-interference ability of the electromagnetic sensor device. In addition, the electromagnetic sensor device can detect the current mutual inductance signal output by the electromagnetic interference device, and after signal processing and control module collection and analysis, the interference correction value and digital notch processing are added to the final liquid level calculation, which reduces the deviation and fluctuation of the final output liquid level signal, and further increases the anti-interference ability of the electromagnetic sensor device. Thirdly, the electromagnetic sensor device removes the original potentiometer, reduces the drift degree of the detection result, and is conducive to enhancing the stability and improving the detection precision of the electromagnetic sensor device. Finally, the electromagnetic sensor device can also measure the phase difference between the excitation signal of the primary excitation coil and the induced signal of the secondary induction coil, and the induced signal of the compensation induction coil, which provides more possibilities for the design of the measurement system of the 3-coil electromagnetic detection principle.

[0130] The device embodiments described above are only schematic, wherein the units described as separate components can or can not be physically separate, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the embodiment.

[0131] From the above description of the 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 can also be implemented by hardware. Based on such understanding, the above technical solutions essentially or in other words make contributions to the related art, which 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 a ROM / RAM, a magnetic disk, an optical disk, etc., and includes a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods described in each embodiment or some parts of the embodiments.

[0132] It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises", "comprising", "includes", "including" and "has" are inclusive and therefore 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 groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order

[0133] The above description is that of current embodiments of the disclosure. Various modifications and changes can be made thereto without departing from the spirit and scope of the disclosure as set forth. The disclosure is not to be limited to the embodi ments described herein but is to cover any and all changes and modifications within the scope and spirit of the disclosure as described.

Claims

1. An electromagnetic sensing device, wherein, The electromagnetic sensing device comprises 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. The control module comprises 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 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, which 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, which 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 representing 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.

2. The electromagnetic sensing device of claim 1, wherein, The control module encapsulates a control unit, a first digital-to-analog conversion circuit, and a first pulse modulation circuit; and the excitation signal adjustment module comprises a modulation circuit and a power amplification circuit. The input end of the first digital-to-analog conversion circuit and the input end of the first pulse modulation circuit are 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 are connected to the input end of the modulation circuit as the second port, the output end of the modulation circuit is connected to the input end of the power amplification circuit, and the output end of the power amplification circuit is connected to the feedback end of the modulation circuit and the primary excitation coil.

3. The electromagnetic sensing device of claim 2, wherein, The control module further 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; and the induction signal conditioning module comprises a first signal amplification circuit, a first operational amplification 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 amplification circuit, and a third operational amplification circuit. 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 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 are connected to the third port. The output end of the second digital-analog conversion circuit is connected with the input end of the first operational amplifier circuit, the output end of the first operational amplifier circuit is connected with the control end of the first band-pass filter circuit; the output end of the second pulse modulation circuit is connected with the control end of the first switch phase detector circuit, the output end of the third pulse modulation circuit is connected with the control end of the second switch phase detector circuit; The secondary induction coil is connected with the input end of the first signal amplification circuit, the output end of the first signal amplification circuit is connected with the input end of the first band-pass filter circuit, the output end of the first band-pass filter circuit is connected with the input end of the first switch phase detector circuit and the input end of the second switch phase detector circuit respectively, the output end of the first switch phase detector circuit is connected with the input end of the first low-pass filter circuit, the output end of the first low-pass filter circuit is connected with the input end of the second operational amplifier circuit, the output end of the second operational amplifier circuit is connected with the input end of the first analog-digital conversion circuit; the output end of the second switch phase detector circuit is connected with the input end of the second low-pass filter circuit, the output end of the second low-pass filter circuit is connected with the input end of the third operational amplifier circuit, the output end of the third operational amplifier circuit is connected with the input end of the second analog-digital conversion circuit.

4. The electromagnetic sensing device of claim 3, wherein, The center frequency of the first band-pass filter circuit is obtained by adjusting the voltage amplitude output by the second digital-analog conversion circuit, and the center frequency of the first band-pass filter circuit is equal to the frequency of the pulse signals output by the second pulse modulation circuit and the third pulse modulation circuit.

5. The electromagnetic sensing device of claim 3, wherein, The device further comprises a compensation induction coil arranged near the secondary induction coil; the control module further encapsulates a third digital-analog conversion circuit, a fourth pulse modulation circuit, a fifth pulse modulation circuit, a third analog-digital conversion circuit and a fourth analog-digital conversion circuit; the induction signal conditioning module further comprises a second signal amplification circuit, a fourth operational amplifier circuit, a second band-pass filter circuit, a third switch phase detector circuit, a fourth switch phase detector 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 input end of the third digital-analog conversion circuit, the input end of the fourth pulse modulation circuit, the input end of the fifth pulse modulation circuit, the output end of the third analog-digital conversion circuit and the output end of the fourth analog-digital conversion circuit are connected with the control unit, and the output end of the third digital-analog conversion circuit, the output end of the fourth pulse modulation circuit and the output end of the fifth pulse modulation circuit are used as the third port; The output end of the third digital-analog conversion circuit is connected with the input end of the fourth operational amplifier circuit, the output end of the fourth operational amplifier circuit is connected with the control end of the second band-pass filter circuit; the output end of the fourth pulse modulation circuit is connected with the control end of the third switch phase detector circuit, the output end of the fifth pulse modulation circuit is connected with the control end of the fourth switch phase detector circuit; The compensation induction coil is connected with the input end of the second signal amplification circuit, the output end of the second signal amplification circuit is connected with the input end of the second band-pass filter circuit, the output end of the second band-pass filter circuit is connected with the input end of the third switch phase detection circuit and the input end of the fourth switch phase detection circuit respectively, the output end of the third switch phase detection circuit is connected with the input end of the third low-pass filter circuit, the output end of the third low-pass filter circuit is connected with the input end of the fifth operational amplifier circuit, and the output end of the fifth operational amplifier circuit is connected with the input end of the third analog-to-digital conversion circuit; the output end of the fourth switch phase detection circuit is connected with the input end of the fourth low-pass filter circuit, the output end of the fourth low-pass filter circuit is connected with the input end of the sixth operational amplifier circuit, and the output end of the sixth operational amplifier circuit is connected with the input end of the fourth analog-to-digital conversion circuit.

6. The electromagnetic sensing device of claim 5, wherein, The center frequency of the second band-pass filter circuit is obtained by adjusting 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 signal output by the fourth pulse modulation circuit and the fifth pulse modulation circuit.

7. The electromagnetic sensing device of claim 5, wherein, The device further comprises an interference signal detection module, and the control module further comprises a fourth port connected with the interference signal detection module. The interference signal detection module is configured to acquire the frequency and amplitude of an interference signal and transmit the frequency and amplitude of the interference signal to the control module through the fourth port.

8. The electromagnetic sensing device of claim 7, wherein, The interference signal detection module comprises 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 comprises an input capture circuit and a fifth analog-to-digital conversion circuit. The output end of the current mutual inductance circuit is connected with the input end of the seventh operational amplifier circuit, the output end of the seventh operational amplifier circuit is connected with the input end of the filter circuit, the output end of the filter circuit is connected with the input end of the comparison circuit and the input end of the detection circuit respectively, the output end of the comparison circuit is connected with the input end of the input capture circuit, the output end of the detection circuit is connected with the input end of the fifth analog-to-digital conversion circuit, and the output end of the input capture circuit and the output end of the fifth analog-to-digital conversion circuit are connected with the control unit.

9. A method of signal conditioning for an electromagnetic sensing device, wherein, The method is applied to the electromagnetic sensing device of any one of claims 1 to 8, and the method comprises: 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 obtained by adjusting 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 method is applied to the electromagnetic sensing device of any one of claims 1 to 8, and the method comprises: The inductive signal conditioning module conditions the inductive information according to a parameter value output by the third port, to obtain a liquid level signal used for representing the to-be-detected liquid level, wherein the parameter value output by the third port is obtained by adjusting the parameter received by the first port based on the parameter adjustment instruction.

10. The method of claim 9, wherein, The control module is internally encapsulated with a control unit, a first digital-to-analog conversion circuit and a first pulse modulation circuit, and is also internally encapsulated with 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 inductive signal conditioning module comprises a first signal amplification circuit, a first operational amplification circuit, a first band-pass filter circuit, a first switched phase detection circuit, a second switched phase detection 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 comprises: acquiring a signal output by the second analog-to-digital conversion circuit; moving 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 as a whole, taking the signal output by the second analog-to-digital conversion circuit as a first feedback signal, so that the first feedback signal has a voltage amplitude close to zero, wherein 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.

11. The method of claim 10, wherein, The device further comprises a compensation inductive coil arranged near the secondary inductive coil; the control module is also internally encapsulated with 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 inductive signal conditioning module further comprises a second signal amplification circuit, a fourth operational amplification circuit, a second band-pass filter circuit, a third switched phase detection circuit, a fourth switched phase detection 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 comprises: acquiring a signal output by the fourth analog-to-digital conversion circuit; moving 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 as a whole, taking the signal output by the fourth analog-to-digital conversion circuit as a second feedback signal, so that the second feedback signal has a voltage amplitude close to 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.

12. The method of claim 11, wherein, The device further comprises an interference signal detection module, which is used to acquire the frequency and amplitude of an interference signal, and the method further comprises: The control unit acquires a first sampling signal obtained by the inductive signal conditioning module after signal conditioning of the secondary inductive coil and a second sampling signal obtained by the inductive signal conditioning module after signal conditioning of the compensation inductive coil, and performs zero calibration on the first sampling signal and the second sampling signal, to obtain a zero calibration coefficient; determine an interference correction value according to the amplitude of the interference signal, and determine a filter coefficient corresponding to a preset digital notch filter in the control unit according to the frequency of the interference signal; perform signal processing on the first sampling signal and the second sampling signal by using the zero-adjusting calibration coefficient, the interference correction value, and the filter coefficient, to obtain the liquid level signal.

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