Capacitance measurement method and circuit based on fuel quantity sensor, aircraft and storage medium

Abstract

The embodiment of the invention provides a capacitance measurement method and circuit based on a fuel quantity sensor, an airplane and a storage medium, and belongs to the technical field of capacitance measurement. The circuit comprises a signal generation module, a current-voltage conversion module, a phase-sensitive detection module, an analog-to-digital conversion module and a control module. According to the embodiment of the invention, the sine wave excitation signal can be generated through the signal generation module, so that the fuel quantity sensor generates the feedback signal according to the sine wave excitation signal, and the first voltage signal and the second voltage signal are obtained through the current-voltage conversion module; a target first real part voltage signal, a target first imaginary part voltage signal, a target second real part voltage signal and a target second imaginary part voltage signal are obtained through a phase-sensitive detection module; the capacitance value is calculated through the control module according to the digitized target first real part voltage signal, the target first imaginary part voltage signal, the target second real part voltage signal and the target second imaginary part voltage signal, the measurement accuracy of the capacitance value is improved, and therefore the measurement accuracy of the oil mass is improved.

Description

Technical Field

[0001] The present application relates to the field of capacitance measurement technology, and in particular to a capacitance measurement method, circuit, aircraft and storage medium based on an oil level sensor. Background Art

[0002] At present, in order to measure the oil level in the aircraft tank, the capacitance value is often obtained through the oil level sensor. The capacitance value is proportional to the oil immersion height of the oil level sensor, that is, the capacitance value reflects the oil level in the tank. Therefore, the measurement accuracy of the capacitance value affects the measurement accuracy of the oil level.

[0003] The signal output by the fuel level sensor can be processed by a capacitance measurement circuit to obtain a voltage, and the capacitance value can be calculated based on the voltage. However, the capacitance value calculated based on the voltage collected by the capacitance measurement circuit often has errors. With the improvement of the technical indicators of the aircraft fuel measurement system, the current capacitance value measurement accuracy can no longer meet the requirements for accurately measuring the fuel level in the aircraft tank.

[0004] Therefore, how to improve the measurement accuracy of capacitance value has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] The main purpose of the embodiments of the present application is to propose a capacitance measurement method, circuit, aircraft and storage medium based on an oil level sensor, aiming to improve the measurement accuracy of the capacitance value.

[0006] To achieve the above-mentioned purpose, a first aspect of an embodiment of the present application proposes a capacitance measurement circuit based on an oil level sensor, comprising: a signal generating module, a flow-pressure conversion module, a phase-sensitive detection module, an analog-to-digital conversion module and a control module;

[0007] The signal generating module is electrically connected to the oil level sensor, and is used to generate a first square wave signal, a second square wave signal and a sine wave excitation signal, so that the oil level sensor generates a feedback signal according to the sine wave excitation signal; wherein the first square wave signal and the second square wave signal have the same frequency and a phase difference of 90 degrees;

[0008] The flow-pressure conversion module is electrically connected to the oil level sensor, and is used to obtain a first voltage signal according to the feedback signal, and to obtain a second voltage signal according to the sinusoidal wave excitation signal and the feedback signal;

[0009] The phase-sensitive detection module is electrically connected to the signal generating module and the current-pressure conversion module, and the phase-sensitive detection module is used to obtain a target first real voltage signal according to the first voltage signal and the first square wave signal, obtain a target first imaginary voltage signal according to the first voltage signal and the second square wave signal, obtain a target second real voltage signal according to the second voltage signal and the first square wave signal, and obtain a target second imaginary voltage signal according to the second voltage signal and the second square wave signal;

[0010] The analog-to-digital conversion module is electrically connected to the phase-sensitive detection module, and the analog-to-digital conversion module is used to digitize the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal;

[0011] The control module is electrically connected to the analog-to-digital conversion module, and is used to obtain the capacitance value of the oil level sensor based on the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal.

[0012] In some embodiments, the oil level sensor-based capacitance measurement circuit further includes:

[0013] A time-sharing excitation module, the time-sharing excitation module is electrically connected to the signal generating module, the flow-pressure conversion module and the control module; wherein the signal generating module is connected to the oil level sensor through the time-sharing excitation module, and the flow-pressure conversion module is connected to the oil level sensor through the time-sharing excitation module; the time-sharing excitation module is used to electrically connect one of the multiple oil level sensors in response to the selection instruction of the control module, so that the selected oil level sensor generates the feedback signal according to the sinusoidal wave excitation signal.

[0014] In some embodiments, the signal generating module includes: a signal source submodule, a signal filtering submodule, a comparison submodule, a zero calibration submodule and an amplification submodule;

[0015] The signal source submodule is electrically connected to the control module, and the signal source submodule is used to generate a first initial sine wave signal, a second initial sine wave signal and a third initial sine wave signal in response to a control instruction of the control module; wherein the first initial sine wave signal, the second initial sine wave signal and the third initial sine wave signal have the same frequency, and the phase difference between the first initial sine wave signal and the second initial sine wave signal is 90 degrees;

[0016] The signal filtering submodule is electrically connected to the signal source submodule, and the signal filtering submodule is used to filter the first initial sinusoidal wave signal to output a first AC sinusoidal wave signal, filter the second initial sinusoidal wave signal to output a second AC sinusoidal wave signal, and filter the third initial sinusoidal wave signal to output a third AC sinusoidal wave signal;

[0017] The comparison submodule is electrically connected to the signal filtering submodule, and the comparison submodule is used to output the first square wave signal according to the first AC sine wave signal, and output the second square wave signal according to the second AC sine wave signal;

[0018] The zero calibration submodule is electrically connected to the signal filtering submodule, and the zero calibration submodule is used to output a standard sine wave signal according to the third AC sine wave signal; wherein the standard sine wave signal is a sine wave signal with an initial phase of zero;

[0019] The amplifying submodule is electrically connected to the zero-calibrating submodule, and the amplifying submodule is used to amplify the standard sine wave signal and output the sine wave excitation signal.

[0020] In some embodiments, the time-sharing excitation module includes: an excitation end switch submodule and a feedback end switch submodule;

[0021] The excitation end switch submodule is electrically connected to the amplifier submodule, the excitation end switch submodule has a first number of output ports, the feedback end switch submodule has a first number of input ports, one interface of each of the oil level sensors is electrically connected to one of the output ports of the excitation end switch submodule, and another interface of each of the oil level sensors is electrically connected to one of the input ports of the feedback end switch submodule;

[0022] The excitation end switch submodule is used to select the output port in response to the gating instruction of the control module, and the feedback end switch submodule is used to select the input port in response to the gating instruction of the control module, so that the oil level sensor corresponding to the output port and the input port generates the feedback signal according to the sinusoidal wave excitation signal.

[0023] In some embodiments, the feedback signal includes a current feedback sub-signal and a voltage feedback sub-signal, and the current-voltage conversion module includes: a feedback end conditioning sub-module and an excitation end conditioning sub-module;

[0024] The feedback-end conditioning submodule is electrically connected to the feedback-end switch submodule, and the feedback-end conditioning submodule is used to obtain the first voltage signal according to the current feedback sub-signal and the voltage feedback sub-signal;

[0025] The excitation end conditioning submodule is electrically connected to the excitation end switch submodule and the feedback end switch submodule, and the excitation end conditioning submodule is used to obtain the second voltage signal according to the sinusoidal wave excitation signal and the voltage feedback subsignal.

[0026] In some embodiments, the phase-sensitive detection module includes: a waveform synthesis submodule and a low-pass filtering submodule;

[0027] The waveform synthesis submodule is electrically connected to the comparison submodule, the feedback end conditioning submodule and the excitation end conditioning submodule, and the waveform synthesis submodule is used to perform waveform synthesis according to the first voltage signal and the first square wave signal to obtain an initial first real voltage signal, perform waveform synthesis according to the first voltage signal and the second square wave signal to obtain an initial first imaginary voltage signal, perform waveform synthesis according to the second voltage signal and the first square wave signal to obtain an initial second real voltage signal, and perform waveform synthesis according to the second voltage signal and the second square wave signal to obtain an initial second imaginary voltage signal;

[0028] The low-pass filtering submodule is electrically connected to the waveform synthesis submodule, and is used to filter the initial first real voltage signal to obtain the target first real voltage signal, filter the initial first imaginary voltage signal to obtain the target first imaginary voltage signal, filter the initial second real voltage signal to obtain the target second real voltage signal, and filter the initial second imaginary voltage signal to obtain the target second imaginary voltage signal.

[0029] To achieve the above-mentioned purpose, a second aspect of an embodiment of the present application proposes an aircraft, comprising the capacitance measurement circuit based on the fuel level sensor described in the first aspect.

[0030] To achieve the above-mentioned purpose, a third aspect of an embodiment of the present application proposes a capacitance measurement method based on an oil level sensor, the method being applied to a control module in a capacitance measurement circuit based on an oil level sensor according to the first aspect, the method comprising:

[0031] Obtaining a capacitance value of the oil level sensor according to the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal;

[0032] The oil amount is determined according to the capacitance value.

[0033] In some embodiments, after obtaining the capacitance value of the fuel level sensor according to the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal, the method further includes:

[0034] The capacitance value is calculated as follows:

[0035]

[0036] Among them, U 11 represents the first real voltage value corresponding to the digitized target first real voltage signal, U 12 represents the first imaginary voltage value corresponding to the digitized target first imaginary voltage signal, U 21 represents the second real voltage value corresponding to the digitized target second real voltage signal, U 22 represents the second imaginary voltage value corresponding to the digitized target second imaginary voltage signal, f represents the frequency of the sinusoidal wave excitation signal, and C represents the capacitance value.

[0037] To achieve the above-mentioned purpose, the fourth aspect of an embodiment of the present application proposes a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method described in the third aspect is implemented.

[0038] The capacitance measurement method, circuit, aircraft and storage medium based on the oil quantity sensor proposed in the present application generate a sinusoidal wave excitation signal through a signal generating module, so that the oil quantity sensor generates a feedback signal according to the sinusoidal wave excitation signal, obtains a first voltage signal and a second voltage signal through a flow-pressure conversion module, obtains a target first real voltage signal, a target first imaginary voltage signal, a target second real voltage signal and a target second imaginary voltage signal through a phase-sensitive detection module, and digitizes the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal through an analog-to-digital conversion module. Since the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal are all obtained by processing the feedback signal generated by the oil quantity sensor according to the sinusoidal wave excitation signal, the above four voltage signals can reflect the capacitance value of the oil quantity sensor, and the deviation between the capacitance value reflected by the above four voltage signals and the actual capacitance value is very close. By calculating the capacitance value through the control module according to the digitized target first real voltage signal, target first imaginary voltage signal, target second real voltage signal and target second imaginary voltage signal, the above-mentioned deviation can be effectively reduced, thereby reducing the influence of circuit measurement error on the measurement accuracy of capacitance value, and thus improving the measurement accuracy of oil amount obtained according to capacitance value. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a module block diagram of a capacitance measurement circuit based on an oil level sensor provided in an embodiment of the present application;

[0040] Figure 2 is a module block diagram of a capacitance measurement circuit based on an oil level sensor provided in another embodiment of the present application;

[0041] Figure 3 It is a module block diagram of the signal generation module;

[0042] Figure 4 It is the circuit schematic diagram of the signal filtering submodule;

[0043] Figure 5 This is the circuit schematic diagram of the zero calibration submodule;

[0044] Figure 6 is a waveform change diagram of the third initial sine wave signal being calibrated to zero using the zero calibration submodule;

[0045] Figure 7 It is the circuit schematic diagram of the amplifier module;

[0046] Figure 8 It is a module block diagram of the time-sharing excitation module and the flow-pressure conversion module;

[0047] Fig. 9 It is the circuit schematic diagram of the time-sharing excitation module;

[0048] Fig.10 It is the circuit schematic diagram of the feedback end conditioning submodule;

[0049] Fig.11 It is the circuit schematic diagram of the excitation end conditioning submodule;

[0050] Fig.12 It is a module block diagram of the phase-sensitive detection module;

[0051] Fig.13 It is the circuit schematic diagram of the waveform synthesis submodule;

[0052] Fig.14 It is the circuit schematic diagram of the low-pass filter submodule;

[0053] Fig.15 It is a flow chart of a capacitance measurement method based on an oil level sensor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0055] It should be noted that, although the functional modules are divided in the device schematic diagram and the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first", "second", etc. in the specification, claims and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0057] First, some nouns involved in this application are analyzed:

[0058] MCU: Microcontroller Unit, also known as single-chip microcomputer or single-chip microcomputer.

[0059] DDS: Direct Digital Synthesis, direct digital frequency synthesis technology.

[0060] The capacitance measurement method based on the fuel level sensor, circuit, aircraft and storage medium provided in the embodiments of the present application are specifically illustrated through the following embodiments. First, the capacitance measurement method based on the fuel level sensor in the embodiments of the present application is described.

[0061] The capacitance measurement method based on the oil level sensor provided in the embodiment of the present application can be applied to the terminal, can also be applied to the server side, and can also be software running in the terminal or the server side. In some embodiments, the terminal can be a smart phone, a tablet computer, a laptop computer, a desktop computer, etc.; the server side can be configured as an independent physical server, or a server cluster or distributed system composed of multiple physical servers, and can also be configured as a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms; the software can be an application that implements the capacitance measurement method based on the oil level sensor, etc., but is not limited to the above forms.

[0062] The present application can be used in many general or special computer system environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, etc. The present application can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present application can also be practiced in distributed computing environments, in which tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media including storage devices.

[0063] Figure 1 The capacitance measurement circuit based on the oil level sensor provided in the embodiment of the present application includes a signal generating module 100, a flow-pressure conversion module 200, a phase-sensitive detection module 300, an analog-to-digital conversion module 400 and a control module 500.

[0064] The signal generating module 100 is electrically connected to the oil level sensor, and is used to generate a first square wave signal, a second square wave signal and a sine wave excitation signal, so that the oil level sensor generates a feedback signal according to the sine wave excitation signal; wherein the first square wave signal and the second square wave signal have the same frequency and a phase difference of 90 degrees;

[0065] The flow-pressure conversion module 200 is electrically connected to the oil level sensor, and is used to obtain a first voltage signal according to the feedback signal, and obtain a second voltage signal according to the sinusoidal wave excitation signal and the feedback signal;

[0066] The phase-sensitive detection module 300 is electrically connected to the signal generating module 100 and the current-pressure conversion module 200. The phase-sensitive detection module 300 is used to obtain a target first real voltage signal according to the first voltage signal and the first square wave signal, obtain a target first imaginary voltage signal according to the first voltage signal and the second square wave signal, obtain a target second real voltage signal according to the second voltage signal and the first square wave signal, and obtain a target second imaginary voltage signal according to the second voltage signal and the second square wave signal;

[0067] The analog-to-digital conversion module 400 is electrically connected to the phase-sensitive detection module 300, and the analog-to-digital conversion module 400 is used to digitize the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal;

[0068] The control module 500 is electrically connected to the analog-to-digital conversion module 400, and is used to obtain the capacitance value of the oil level sensor according to the digitized target first real voltage signal, target first imaginary voltage signal, target second real voltage signal and target second imaginary voltage signal.

[0069] It should be noted that the capacitance measurement circuit based on the oil level sensor also includes a power supply module. The voltages provided by the power supply module include +2.5V, +3.3V, +5V, +10V and -10V. The power supply module includes a DC / DC direct current power supply and a regulated power supply.

[0070] Specifically, the oil level sensor is a variable dielectric capacitive sensor.

[0071] Specifically, the phase of the first square wave signal is 0 degrees, and the phase of the second square wave signal is 90 degrees.

[0072] Specifically, the signal generating module 100 is a DDS signal generator, the analog-to-digital conversion module 400 is an A / D conversion chip, and the control module 500 is a microcontroller unit (MCU).

[0073] Specifically, the model of the A / D conversion chip is SAD7656, the measurement accuracy reaches the fourth decimal place, and negative voltage can be collected. Due to the requirements of sampling rate, volume and cost, the common analog-to-digital converter (ADC) is usually a 12-bit 100K sampling rate, and the accuracy of the converted capacitance measurement (i.e., the minimum resolution) is 0.5pf. In this embodiment, the minimum resolution of the analog-to-digital conversion module 400 is 0.1pf.

[0074] The beneficial effects of the embodiments of the present application include but are not limited to:

[0075] The existing capacitance measurement circuit generally obtains the voltage of the oil level sensor, and obtains the capacitance value of the oil level sensor according to a single voltage calculation. Among them, the voltage and the capacitance value are in a linear relationship, so the measurement error of the voltage is also in a linear relationship with the measurement error of the capacitance value. In the present application, since the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal are all obtained by processing the feedback signal generated by the oil level sensor according to the sine wave excitation signal, the above four voltage signals can reflect the capacitance value of the oil level sensor, and the deviation between the capacitance value reflected by the above four voltage signals and the actual capacitance value is very close. The capacitance value is calculated by the control module 500 according to the proportional relationship of the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal. By the proportional relationship in the calculation formula, the above deviation can be effectively reduced, thereby reducing the influence of the circuit measurement error on the measurement accuracy of the capacitance value, and then improving the measurement accuracy of the oil amount obtained according to the capacitance value.

[0076] See also Figure 2 In some embodiments, the capacitance measurement circuit based on the oil level sensor further includes: a time-sharing excitation module 600, the time-sharing excitation module 600 is electrically connected to the signal generating module 100, the flow-pressure conversion module 200 and the control module 500; wherein, the signal generating module 100 is connected to the oil level sensor through the time-sharing excitation module 600, and the flow-pressure conversion module 200 is connected to the oil level sensor through the time-sharing excitation module 600; the time-sharing excitation module 600 is used to electrically connect one of the multiple oil level sensors in response to the selection instruction of the control module 500, so that the selected oil level sensor generates a feedback signal according to the sinusoidal wave excitation signal.

[0077] It should be noted that if multiple oil level sensors need to be connected, the signal generating module 100 and the flow-pressure conversion module 200 are indirectly connected to the multiple oil level sensors through the time-sharing excitation module 600 respectively.

[0078] Specifically, the overall excitation cycle is related to the switching time of the time-sharing excitation module 600 and the number of oil level sensors, wherein the overall excitation cycle refers to the time required to send the sinusoidal wave excitation signal to all oil level sensors. For example, the time-sharing excitation module 600 is switched according to the gating control amount sent by the control module 500, and the switching time of the time-sharing excitation module 600 is 10ms, then the overall excitation cycle of 8 oil level sensors is 80ms.

[0079] The advantage of this embodiment is that multiple oil level sensors are connected via the time-sharing excitation module 600, and one of the multiple oil level sensors is electrically connected in response to the selection instruction of the control module 500, so that the selected oil level sensor generates a feedback signal according to the sinusoidal wave excitation signal, thereby performing time-sharing selection on the multiple oil level sensors and obtaining the feedback signal generated by each oil level sensor according to the same sinusoidal wave excitation signal.

[0080] See also Figure 3 , in some embodiments, the signal generating module 100 includes: a signal source submodule 110, a signal filtering submodule 120, a comparing submodule 130, a zero calibration submodule 140 and an amplifying submodule 150;

[0081] The signal source submodule 110 is electrically connected to the control module 500, and the signal source submodule 110 is used to generate a first initial sine wave signal, a second initial sine wave signal, and a third initial sine wave signal in response to a control instruction of the control module 500; wherein the first initial sine wave signal, the second initial sine wave signal, and the third initial sine wave signal have the same frequency, and the phase difference between the first initial sine wave signal and the second initial sine wave signal is 90 degrees;

[0082] The signal filtering submodule 120 is electrically connected to the signal source submodule 110, and the signal filtering submodule 120 is used to filter the first initial sinusoidal wave signal to output a first AC sinusoidal wave signal, filter the second initial sinusoidal wave signal to output a second AC sinusoidal wave signal, and filter the third initial sinusoidal wave signal to output a third AC sinusoidal wave signal;

[0083] The comparison submodule 130 is electrically connected to the signal filtering submodule 120, and the comparison submodule 130 is used to output a first square wave signal according to the first AC sine wave signal, and output a second square wave signal according to the second AC sine wave signal;

[0084] The zero calibration submodule 140 is electrically connected to the signal filtering submodule 120, and the zero calibration submodule 140 is used to output a standard sine wave signal according to the third AC sine wave signal; wherein the standard sine wave signal is a sine wave signal with an initial phase of zero;

[0085] The amplifying submodule 150 is electrically connected to the zero-calibrating submodule 140 . The amplifying submodule 150 is used to amplify the standard sinusoidal wave signal and output a sinusoidal wave excitation signal.

[0086] Specifically, the signal source submodule 110 is a digital synthesis chip JDDS9851, and the frequency of the initial sinusoidal wave signal output by the signal source submodule 110 is 100 kHz.

[0087] Specifically, the comparison submodule 130 is a comparator, which is used to convert the sine wave signal into a square wave signal.

[0088] Specifically, the signal filtering submodule 120 is an elliptical filter composed of capacitors, inductors and resistors, and the cutoff frequency of the elliptical filter may be 25 MHz. The elliptical filter may use an inductor with a 10% error and a capacitor with a 5% error.

[0089] Specifically, the voltage value of the third initial sine wave signal ranges from 0 to 3.5 V. In one embodiment, the voltage value of the third initial sine wave signal is 1.8 V.

[0090] It should be noted that the signal source submodule 110 can only output a sine wave signal, and cannot directly output a square wave signal. Therefore, the first initial sine wave signal is filtered by the signal filtering submodule 120 to output a first AC sine wave signal, and the second initial sine wave signal is filtered to output a second AC sine wave signal. Then, the comparison submodule 130 outputs a first square wave signal according to the first AC sine wave signal, and outputs a second square wave signal according to the second AC sine wave signal, so that the first square wave signal and the second square wave signal are output to the phase-sensitive detection module 300.

[0091] It should be noted that the signal source submodule 110 may also only generate the first initial sine wave signal and the second initial sine wave signal, and then obtain the sine wave excitation signal according to one of the sine wave signals. However, the sine wave excitation signal obtained by this method has the same phase as the first square wave or the second square wave, which may cause the waveform of the signal (such as the target first real voltage signal) obtained by superimposing the voltage signal on the square wave signal in the phase-sensitive detection module 300 to be close to an odd function, further causing the voltage value corresponding to the digital signal obtained after digitizing the signal through the integral analog-to-digital converter to be close to zero, making it difficult to calculate the capacitance value of the oil level sensor. Therefore, the advantage of the signal source submodule 110 generating the first initial sine wave signal, the second initial sine wave signal and the third initial sine wave signal is that the phase of the third initial sine wave signal can be adjusted arbitrarily, thereby affecting the phase of the sine wave excitation signal obtained according to the third initial sine wave signal, so as to adjust the value range of the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal, and improve the reliability of the calculated capacitance value of the oil level sensor.

[0092] It should be noted that the sine wave generated by the signal source submodule 110 contains a lot of high-frequency clutter.

[0093] The advantage of this embodiment is that the sine wave generated by the excitation signal source is subjected to high-frequency filtering by the signal filtering submodule 120, thereby filtering out high-frequency clutter, improving signal clarity and signal quality, and reducing the impact of high-frequency clutter on the next-level circuit. The AC sine wave signal is processed by the zero calibration submodule 140 to remove the DC component and output a standard sine wave signal with an initial phase of zero, thereby eliminating the circuit zero point deviation, improving the measurement accuracy, and making the measurement result of the circuit more accurate. The standard sine wave signal is amplified by the amplifier submodule 150 and then output as a sine wave excitation signal, thereby increasing the power of the sine wave excitation signal.

[0094] See also Figure 3 and Figure 4 In some embodiments, the signal filtering submodule 120 includes a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a first resistor R1, a second resistor R2, a first inductor L1, and a second inductor L2. The first resistor R1 is electrically connected to the first inductor L1, the first capacitor C1, and the third capacitor C3, the first capacitor C1 is electrically connected to the second inductor L2, the second capacitor C2, and the fourth capacitor C4, and the second capacitor C2 is electrically connected to the fifth capacitor C5 and the second resistor R2. The third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, the first resistor R1, and the second resistor R2 are grounded.

[0095] It should be noted that the Psign ​​port inputs the first initial sine wave signal, the second initial sine wave signal and the third initial sine wave signal, the first AC sine wave signal and the second initial sine wave signal are output to the comparison submodule 130 through the Psine port, and the third initial sine wave signal is output to the zero calibration submodule 140 through the Psine port.

[0096] See also Figure 3 and Figure 5 In some embodiments, the zero calibration submodule 140 includes a first operational amplifier OP1, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and an adjustable resistor Rf. One end of the adjustable resistor Rf is connected to the analog ground AGND, the other end of the adjustable resistor Rf is electrically connected to the third resistor R3 and the first operational amplifier OP1, and the fourth resistor R4 is electrically connected to the fifth resistor R5 and the first operational amplifier OP1.

[0097] Specifically, the first operational amplifier OP1 in the zero calibration submodule 140 is a high-speed operational amplifier, and the model of the first operational amplifier OP1 is GF467.

[0098] It should be noted that the voltage provided by the first regulated power supply VB1 is +10V, and the voltage provided by the second regulated power supply VB2 is -10V.

[0099] It should be noted that the standard sine wave signal is output to the amplifying submodule 150 through the Pout port.

[0100] It should be noted that the calculation formula for the voltage value of the standard sine wave signal is:

[0101]

[0102] Wherein, Vout is the voltage value of the standard sinusoidal wave signal, and Vsine is the voltage value of the third initial sinusoidal wave signal.

[0103] like Figure 6 As shown, the zero calibration submodule 140 performs waveform transformation on the third initial sinusoidal wave signal to obtain a standard sinusoidal wave signal with an initial phase of zero. Figure 6 Usine refers to the third initial sine wave signal, and Uout refers to the standard sine wave signal.

[0104] See also Figure 3 and Figure 7 In some embodiments, the amplification submodule 150 includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a second operational amplifier OP2, and a third operational amplifier OP3. The sixth resistor R6 is electrically connected to the second operational amplifier OP2, one end of the seventh resistor R7 is connected to the analog ground AGND, the other end of the seventh resistor R7 is electrically connected to the eighth resistor R8 and the second operational amplifier OP2, and the second operational amplifier OP2 is electrically connected to the third operational amplifier OP3.

[0105] It should be noted that the sinusoidal wave excitation signal is output to the time-sharing excitation module 600 through the Php port.

[0106] It should be noted that the calculation formula for the voltage value of the sine wave excitation signal is:

[0107]

[0108] Wherein, Vhp is the voltage value of the sinusoidal wave excitation signal, and Vout is the voltage value of the standard sinusoidal wave signal.

[0109] Specifically, the operational amplifiers (including the second operational amplifier OP2 and the third operational amplifier OP3) in the amplifier submodule 150 are rail-to-rail operational amplifiers. The input voltage swing and output voltage swing of the rail-to-rail operational amplifier are very close to or almost equal to the power supply voltage value. The advantage of this embodiment is that the amplifier submodule 150 uses a rail-to-rail operational amplifier, which can better process various input signals and expand the range of output signals, thereby improving the performance and stability of the system.

[0110] In some embodiments, the signal generating module 100 further includes a voltage dividing circuit. The voltage dividing circuit is electrically connected to the amplifying submodule 150 and the comparing submodule 130, and the comparing submodule 130 is electrically connected to the control module 500. The voltage dividing circuit is used to divide the sine wave excitation signal to obtain a divided excitation signal, and send the sine wave excitation signal and the divided excitation signal to the comparing submodule 130, so that the comparing submodule 130 outputs a square wave signal with the same frequency as the sine wave excitation signal to the control module 500 when the voltage of the sine wave excitation signal is greater than the voltage of the divided excitation signal, so that the control module 500 obtains the frequency of the sine wave excitation signal according to the square wave signal with the same frequency as the sine wave excitation signal.

[0111] See also Figure 8 In some embodiments, the time-sharing excitation module 600 includes: an excitation end switch submodule 610 and a feedback end switch submodule 620. The excitation end switch submodule 610 is electrically connected to the amplifier submodule 150, the excitation end switch submodule 610 has a first number of output ports, the feedback end switch submodule 620 has a first number of input ports, one interface of each oil level sensor is electrically connected to an output port of the excitation end switch submodule 610, and another interface of each oil level sensor is electrically connected to an input port of the feedback end switch submodule 620. The excitation end switch submodule 610 is used to select the output port in response to the gating instruction of the control module 500, and the feedback end switch submodule 620 is used to select the input port in response to the gating instruction of the control module 500, so that the oil level sensor corresponding to the output port and the input port generates a feedback signal according to the sinusoidal wave excitation signal.

[0112] The advantage of this embodiment is that the excitation end switch submodule 610 controls the on and off of the switch in response to the on command of the control module 500, and only one of the first number of output channels is connected at a certain moment; the feedback end switch submodule 620 controls the on and off of the switch in response to the on command of the control module 500, and only one of the first number of input ports is connected at a certain moment, and the connected output channel and the connected input port are connected to the same oil level sensor, thereby controlling only one of the multiple oil level sensors to be connected at a certain moment, so that the selected oil level sensor generates a feedback signal according to the sinusoidal wave excitation signal.

[0113] See also Figure 8In some embodiments, the feedback signal includes a current feedback sub-signal and a voltage feedback sub-signal. The current-to-voltage conversion module 200 includes: a feedback end conditioning sub-module 210 and an excitation end conditioning sub-module 220. The feedback end conditioning sub-module 210 is electrically connected to the feedback end switch sub-module 620, and the feedback end conditioning sub-module 210 is used to obtain a first voltage signal according to the current feedback sub-signal and the voltage feedback sub-signal. The excitation end conditioning sub-module 220 is electrically connected to the excitation end switch sub-module 610 and the feedback end switch sub-module 620, and the excitation end conditioning sub-module 220 is used to obtain a second voltage signal according to the sinusoidal wave excitation signal and the voltage feedback sub-signal.

[0114] It should be noted that the voltage value of the first voltage signal is equal to the voltage value of the current feedback sub-signal converted into a voltage signal minus the voltage value of the voltage feedback sub-signal. The voltage value of the second voltage signal is equal to the voltage value of the sinusoidal excitation signal minus the voltage value of the voltage feedback sub-signal.

[0115] It should be noted that the sinusoidal wave excitation signal and the voltage feedback sub-signal reflect the voltage across the fuel level sensor.

[0116] It should be noted that the current value of the current feedback sub-signal reflects the current value flowing through the oil level sensor.

[0117] The advantage of this embodiment is that the current feedback sub-signal is converted into a voltage signal through the feedback end conditioning sub-module 210, thereby improving the strength of the signal. A first voltage signal is obtained according to the current feedback sub-signal and the voltage feedback sub-signal, and a second voltage signal is obtained according to the sine wave excitation signal and the voltage feedback sub-signal through the excitation end conditioning sub-module 220. In addition, interference signals are eliminated and signals are conditioned through the feedback end conditioning sub-module 210 and the excitation end conditioning sub-module 220, thereby enhancing the stability and anti-interference ability of the signal.

[0118] See also Fig. 9 In some embodiments, the time-sharing excitation module 600 includes an excitation end switch submodule 610, a feedback end switch submodule 620, and a single-pole double-throw switch 630. The excitation end switch submodule 610 and the feedback end switch submodule 620 are both composed of two analog switches.

[0119] Specifically, the analog switch is an 8-channel analog switch, and the model of the analog switch is GCC4051B.

[0120] Specifically, 16 oil level sensors may be connected between the excitation end switch submodule 610 and the feedback end switch submodule 620 .

[0121] Specifically, in one embodiment, two ports in the feedback end switch submodule 620 are grounded, and 14 oil level sensors can be connected between the excitation end switch submodule 610 and the feedback end switch submodule 620. It should be noted that electronic components may have temperature drift (referred to as temperature drift). By selecting the ground port of the analog switch in the feedback end switch submodule 620, the circuit is zeroed, thereby reducing the influence of temperature drift on the measurement result and improving the accuracy of the data.

[0122] Specifically, in another embodiment, two ports in the feedback end switch submodule 620 are used for grounding for calibration, and four ports of the excitation end switch submodule 610 and four ports of the feedback end switch submodule 620 are used to connect calibration elements, then 10 oil level sensors can be connected between the excitation end switch submodule 610 and the feedback end switch submodule 620.

[0123] Specifically, in another embodiment, eight oil level sensors are connected between the excitation end switch submodule 610 and the feedback end switch submodule 620 .

[0124] It should be noted that the address selection end of the analog switch receives the address selection instruction sent by the control module 500, and the enable end of the analog switch receives the enable instruction sent by the control module 500. The analog switch responds to the address selection instruction and enable instruction selection port of the control module 500.

[0125] It should be noted that one of the two moving contacts in the single-pole double-throw switch 630 is connected to the Php port, and the other is connected to the analog ground AGND, and the static contact in the single-pole double-throw switch 630 is connected to the PB port. The Pctrl port inputs the control instruction sent by the control module 500, and the single-pole double-throw switch 630 switches the switch according to the control instruction. When the Php port is connected to the PB port, the sinusoidal wave excitation signal is input to the excitation end switch submodule 610 through the Php port and the PB port, and the sinusoidal wave excitation signal is output to the selected oil level sensor through the excitation end switch submodule 610. The oil level sensor generates a feedback signal (including Fig. 9 The current feedback sub-signal and the voltage feedback sub-signal in the feedback module are input to the feedback terminal switch sub-module 620, and the feedback signal is transmitted to the Pfb port through the feedback terminal switch sub-module 620.

[0126] See also Fig.10In some embodiments, the feedback end conditioning submodule 210 includes a fourth operational amplifier OP4, a fifth operational amplifier OP5, a sixth operational amplifier OP6, a seventh operational amplifier OP7, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12 and a thirteenth resistor R13. A non-inverting input terminal of the fourth operational amplifier OP4 is connected to the analog ground AGND, a ninth resistor R9 is electrically connected to an inverting input terminal of the fourth operational amplifier OP4 and an output terminal of the fourth operational amplifier OP4, an output terminal of the fourth operational amplifier OP4 is electrically connected to an inverting input terminal of the sixth operational amplifier OP6, a non-inverting input terminal of the sixth operational amplifier OP6 is electrically connected to an output terminal of the sixth operational amplifier OP6, and an output terminal of the sixth operational amplifier OP6 is electrically connected to a twelfth resistor R12; a non-inverting input terminal of the fifth operational amplifier OP5 is electrically connected to an output terminal of the fifth operational amplifier OP5, an output terminal of the fifth operational amplifier OP5 is electrically connected to a tenth resistor R10, one end of an eleventh resistor R11 is connected to the analog ground AGND, the other end of the eleventh resistor R11 is electrically connected to the tenth resistor R10 and an inverting input terminal of the seventh operational amplifier OP7, one end of a thirteenth resistor R13 is electrically connected to the twelfth resistor R12 and a non-inverting input terminal of the seventh operational amplifier OP7, and the other end of the thirteenth resistor R13 is electrically connected to an output terminal of the seventh operational amplifier OP7.

[0127] Specifically, the model of the fourth operational amplifier OP4 is F412A, and the models of other operational amplifiers in the feedback-end conditioning submodule 210 are FX084.

[0128] It should be noted that the Pfb port inputs the current feedback sub-signal and the voltage feedback sub-signal, the current feedback sub-signal is output to the fourth operational amplifier OP4 through the Pfb port, and the voltage feedback sub-signal is output to the fifth operational amplifier OP5 through the Pfb port.

[0129] It should be noted that the first voltage signal is output to the phase-sensitive detection circuit through the P1 port.

[0130] It should be noted that the current feedback sub-signal obtained by the oil level sensor in the fuel tank according to the sine wave excitation signal is a weak current signal, which is not easy to be measured and calculated, so it needs to be converted into a voltage signal first. The advantage of this embodiment is that the fifth operational amplifier OP5 and the ninth resistor R9 in the feedback end conditioning submodule 210 form a flow-voltage conversion circuit, and the current feedback sub-signal is converted into a voltage signal, thereby improving the strength of the signal. The fifth operational amplifier OP5, the sixth operational amplifier OP6, the tenth resistor R10, the eleventh resistor R11 and the twelfth resistor R12 form an emitter-follower circuit, and the voltage signal converted from the current feedback sub-signal and the voltage feedback sub-signal are input into the emitter-follower circuit to eliminate the interference signal, and the signal is conditioned to enhance the stability and anti-interference ability of the signal. Through the seventh operational amplifier OP7 and the thirteenth resistor R13, a first voltage signal is obtained according to the current feedback sub-signal and the voltage feedback sub-signal.

[0131] See also Fig.11In some embodiments, the excitation end conditioning submodule 220 includes an eighth operational amplifier OP8, a ninth operational amplifier OP9, a tenth operational amplifier OP10, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, and a seventeenth resistor R17. The inverting input terminal of the eighth operational amplifier OP8 is electrically connected to the output terminal of the eighth operational amplifier OP8, the output terminal of the eighth operational amplifier OP8 is electrically connected to the fourteenth resistor R14, one end of the fifteenth resistor R15 is connected to the analog ground AGND, and the other end of the fifteenth resistor R15 is electrically connected to the fourteenth resistor R14 and the positive input terminal of the tenth operational amplifier OP10; the inverting input terminal of the ninth operational amplifier OP9 is electrically connected to the output terminal of the ninth operational amplifier OP9, the output terminal of the ninth operational amplifier OP9 is electrically connected to the sixteenth resistor R16, one end of the seventeenth resistor R17 is electrically connected to the sixteenth resistor R16 and the inverting input terminal of the tenth operational amplifier OP10, and the other end of the seventeenth resistor R17 is electrically connected to the output terminal of the tenth operational amplifier OP10.

[0132] Specifically, the resistance values ​​of the fourteenth resistor R14, the fifteenth resistor R15, the sixteenth resistor R16 and the seventeenth resistor R17 are all the same.

[0133] Specifically, the model of the operational amplifier in the excitation end conditioning submodule 220 is FX084.

[0134] Specifically, the resistors in the feedback-end conditioning submodule 210 and the excitation-end conditioning submodule 220 are non-inductive metal foil resistors, and the model is RJ711.

[0135] It should be noted that the voltage feedback sub-signal is output to the eighth operational amplifier OP8 through the Pfb port.

[0136] It should be noted that the sine wave excitation signal is output to the ninth operational amplifier OP9 through the Php port.

[0137] The advantage of this embodiment is that the eighth operational amplifier OP8, the ninth operational amplifier OP9, the fourteenth resistor R14, the fifteenth resistor R15 and the sixteenth resistor R16 form an emitter-follower circuit to isolate the front and rear stage circuits, and the voltage feedback sub-signal and the sine wave excitation signal are input into the emitter-follower circuit to eliminate the interference signal, condition the signal, and enhance the stability and anti-interference ability of the signal. Through the tenth operational amplifier OP10 and the seventeenth resistor R17, the second voltage signal is obtained according to the sine wave excitation signal and the voltage feedback sub-signal.

[0138] See also Fig.12 In some embodiments, the phase-sensitive detection module 300 includes: a waveform synthesis submodule 310 and a low-pass filtering submodule 320 .

[0139] The waveform synthesis submodule 310 is electrically connected to the comparison submodule 130, the feedback end conditioning submodule 210 and the excitation end conditioning submodule 220. The waveform synthesis submodule 310 is used to perform waveform synthesis according to the first voltage signal and the first square wave signal to obtain an initial first real voltage signal, perform waveform synthesis according to the first voltage signal and the second square wave signal to obtain an initial first imaginary voltage signal, perform waveform synthesis according to the second voltage signal and the first square wave signal to obtain an initial second real voltage signal, and perform waveform synthesis according to the second voltage signal and the second square wave signal to obtain an initial second imaginary voltage signal.

[0140] The low-pass filtering submodule 320 is electrically connected to the waveform synthesis submodule 310, and is used to filter the initial first real voltage signal to obtain a target first real voltage signal, filter the initial first imaginary voltage signal to obtain a target first imaginary voltage signal, filter the initial second real voltage signal to obtain a target second real voltage signal, and filter the initial second imaginary voltage signal to obtain a target second imaginary voltage signal.

[0141] It should be noted that the signal obtained after filtering by the low-pass filter submodule 320 is the DC component of the input signal. For example, the target first real voltage signal is the DC component of the initial first real voltage signal.

[0142] The advantage of this embodiment is that the waveform synthesis submodule 310 performs waveform synthesis to obtain an initial first real voltage signal, an initial first imaginary voltage signal, an initial second real voltage signal and an initial second imaginary voltage signal. The low-pass filtering submodule 320 performs filtering to obtain a target first real voltage signal, a target first imaginary voltage signal, a target second real voltage signal and a target second imaginary voltage signal, thereby retaining only the DC component of the signal.

[0143] See also Fig.13 In some embodiments, the waveform synthesis submodule 310 includes a 4-to-2 analog switch and a 2-to-1 analog switch. The 4-to-2 analog switch is electrically connected to the 2-to-1 analog switch, and the 2-to-1 analog switch is connected to the analog ground AGND.

[0144] Specifically, the model of the 4-to-2 analog switch is GCC4052B, and the model of the 2-to-1 analog switch is GCC4053B.

[0145] It should be noted that the address gating terminal of the 4-to-2 analog switch receives the address gating instruction sent by the control module 500 , and the 4-to-2 analog switch responds to the address gating instruction and the enable instruction gating port of the control module 500 .

[0146] It should be noted that the input terminal of the 4-to-2 analog switch (i.e. Fig.13The first voltage signal and the second voltage signal are input to the X0 port, the X1 port, the X2 port and the X3 port in the 4-to-2 analog switch control terminal (i.e. Fig.13 The Y0 port, Y1 port, Y2 port and Y3 port of the 4-to-2 analog switch input the first square wave signal and the second square wave signal. The Y port of the 4-to-2 analog switch outputs the first square wave signal or the second square wave signal to the B port of the 2-to-1 analog switch, and the X port of the 4-to-2 analog switch outputs the first voltage signal or the second voltage signal to the bY port of the 2-to-1 analog switch.

[0147] It should be noted that the Psyn port outputs the initial first real voltage signal, the initial first imaginary voltage signal, the initial second real voltage signal or the initial second imaginary voltage signal to the low-pass filtering submodule 320 .

[0148] It should be noted that in Fig.13 In the figure, U1 is the first voltage signal, U2 is the second voltage signal, PWM1 is the first square wave signal, and PWM2 is the second square wave signal.

[0149] See also Fig.14 In some embodiments, the low-pass filter submodule 320 includes an eleventh operational amplifier OP11, a twelfth operational amplifier OP12, a sixth capacitor C6, a seventh capacitor C7, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, and a twenty-first resistor R21. The eighteenth resistor R18 is electrically connected to the nineteenth resistor R19 and the seventh capacitor C7, the nineteenth resistor R19 is electrically connected to the sixth capacitor C6, the sixth capacitor C6 is electrically connected to the twentieth resistor R20, the sixth capacitor C6 and the twenty-first resistor R20 are connected to the analog ground AGND, the twentieth resistor R20 is electrically connected to the eleventh operational amplifier OP11 and the twenty-first resistor R21, and the twenty-first resistor R21 is electrically connected to the seventh capacitor C7, the eleventh operational amplifier OP11, and the twelfth operational amplifier OP12.

[0150] It should be noted that the Pan port outputs the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal to the analog-to-digital conversion module 400 .

[0151] Specifically, the model of the operational amplifiers (including the eleventh operational amplifier OP11 and the twelfth operational amplifier OP12 ) in the low-pass filter submodule 320 is FX084.

[0152] It should be noted that the 3dB cutoff frequency of the operational amplifier in the low-pass filter submodule 320 is equal to the preset signal frequency of the sine wave excitation signal. The formula for the 3dB cutoff frequency of the operational amplifier in the low-pass filter submodule 320 is:

[0153]

[0154] Wherein, FL is the 3 dB cutoff frequency of the operational amplifier in the low-pass filter submodule 320 , in Hz.

[0155] It should be noted that the formula for the amplification factor of the low-pass filter submodule 320 is:

[0156]

[0157] Wherein, K is the gain factor of the low-pass filter submodule 320 .

[0158] For example, when the preset signal frequency of the sine wave excitation signal is 100 Hz, the resistance values ​​of the eighteenth resistor R18 and the nineteenth resistor R19 are 15.9 kΩ (kilo-ohms), the resistance value of the twentieth resistor R20 is 86.19 kΩ, and the resistance value of the twenty-first resistor R21 is 50.59 kΩ. The capacitance values ​​of the sixth capacitor C6 and the seventh capacitor C7 are 0.1 μF (microfarads). According to the above formula, the 3 dB cut-off frequency of the operational amplifier is calculated to be approximately equal to 100 Hz, and the amplification factor of the low-pass filter submodule 320 is approximately equal to 1.6.

[0159] It should be noted that, according to the calculation result of the Fourier expansion, the DC component of the voltage signal is 1 / π times the voltage signal, so the theoretical value of K is 3.14. However, according to the actual measurement results, when the preset signal frequency of the sinusoidal wave excitation signal is 100Hz, the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal are obtained by the low-pass filtering submodule 320 with K set to 1.6, and the capacitance value calculated according to the voltage values ​​of these four signals is closer to the preset capacitance value. In summary, K is set to 1.6 to improve the measurement accuracy of the capacitance value.

[0160] An embodiment of the present application also provides an aircraft, which includes the above-mentioned capacitance measurement circuit based on the oil level sensor.

[0161] The specific structure and function of the capacitance measurement circuit based on the fuel level sensor in the aircraft are substantially the same as the specific embodiment of the capacitance measurement circuit based on the fuel level sensor described above, and will not be described in detail herein.

[0162] The advantage of this embodiment is that a sinusoidal excitation signal is generated by the signal generating module 100, so that the oil level sensor generates a feedback signal according to the sinusoidal excitation signal, a first voltage signal and a second voltage signal are obtained by the flow-pressure conversion module 200, a target first real voltage signal, a target first imaginary voltage signal, a target second real voltage signal and a target second imaginary voltage signal are obtained by the phase-sensitive detection module 300, and the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal are digitized by the analog-to-digital conversion module 400. Since the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal are all obtained by processing the feedback signal generated by the oil level sensor according to the sinusoidal excitation signal, the above four voltage signals can reflect the capacitance value of the oil level sensor, and the deviation between the capacitance value reflected by the above four voltage signals and the actual capacitance value is very close. By calculating the capacitance value according to the digitized target first real voltage signal, target first imaginary voltage signal, target second real voltage signal and target second imaginary voltage signal through the control module 500, the above-mentioned deviation can be effectively reduced, thereby reducing the influence of the circuit measurement error on the measurement accuracy of the capacitance value, and further improving the measurement accuracy of the oil amount obtained according to the capacitance value.

[0163] See also Fig.15 The embodiment of the present application further provides a capacitance measurement method based on an oil level sensor. The capacitance measurement method based on an oil level sensor is applied to the control module 500 in the capacitance measurement circuit based on the oil level sensor. The capacitance measurement method based on an oil level sensor includes:

[0164] S101, obtaining a capacitance value of the fuel level sensor according to the digitized target first real voltage signal, target first imaginary voltage signal, target second real voltage signal and target second imaginary voltage signal.

[0165] S102, determining the oil amount according to the capacitance value.

[0166] In some embodiments, after obtaining the capacitance value of the fuel level sensor according to the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal, the capacitance measurement method based on the fuel level sensor further includes:

[0167] The capacitance value is calculated as:

[0168]

[0169] Among them, U 11 represents the first real voltage value corresponding to the digitized target first real voltage signal, U 12represents the first imaginary voltage value corresponding to the digitized target first imaginary voltage signal, U 21 represents the second real voltage value corresponding to the digitized target second real voltage signal, U 22 represents the second imaginary voltage value corresponding to the digitized target second imaginary voltage signal, f represents the frequency of the sinusoidal wave excitation signal, and C represents the capacitance value.

[0170] Specifically, the frequency of the sinusoidal wave excitation signal may be 100 Hz.

[0171] The beneficial effects of the embodiments of the present application include but are not limited to:

[0172] Existing capacitance measurement methods generally calculate the capacitance value of the oil level sensor according to the voltage, and the calculated capacitance value is linearly related to the voltage, so the measurement error of the voltage is also linearly related to the measurement error of the capacitance value. In the present application, since the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal are all obtained by processing the feedback signal generated by the oil level sensor according to the sine wave excitation signal, the above four voltage signals can reflect the capacitance value of the oil level sensor, and the deviation between the capacitance value reflected by the above four voltage signals and the actual capacitance value is very close. The capacitance value is calculated by the control module 500 according to the proportional relationship of the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal. By calculating the proportional relationship of the voltage signal in the formula, the above deviation can be effectively reduced, thereby reducing the influence of the circuit measurement error on the measurement accuracy of the capacitance value, and then improving the measurement accuracy of the oil amount obtained according to the capacitance value.

[0173] In some embodiments, before obtaining the capacitance value of the fuel level sensor according to the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal, the capacitance measurement method based on the fuel level sensor further includes:

[0174] A sine wave excitation signal is obtained, and if the frequency of the sine wave excitation signal is not equal to the preset signal frequency, a calibration instruction is generated according to the preset signal frequency, and the calibration instruction is sent to the signal generating module 100, so that the signal generating module 100 responds to the calibration instruction and calibrates the sine wave excitation signal according to the preset signal frequency. The calibration instruction includes the preset signal frequency.

[0175] The advantage of this embodiment is that the sine wave excitation signal is monitored and calibrated by the control module 500, thereby improving the stability and reliability of the signal.

[0176] In some embodiments, the capacitance measurement circuit based on the oil level sensor further includes a storage module, which is electrically connected to the control module 500. Determining the oil level according to the capacitance value includes: searching through the storage module according to the capacitance value to obtain the oil level.

[0177] Specifically, the storage module may be a flash memory. It should be noted that after the capacitance value is calculated, the oil volume is obtained by searching the corresponding relationship between the capacitance value and the oil volume in the data table in the storage module.

[0178] In some embodiments, after obtaining the capacitance value of the fuel level sensor according to the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal, the capacitance measurement method based on the fuel level sensor further includes:

[0179] The total impedance of the circuit is obtained according to the capacitance value, the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal; the calculation formula of the total impedance of the circuit is:

[0180]

[0181] Wherein, Z represents the total impedance of the circuit, f represents the frequency of the sinusoidal wave excitation signal, C represents the capacitance value, j represents the imaginary unit, and R represents the series equivalent resistance of the oil level sensor;

[0182] The calculation formula for R is:

[0183]

[0184] Among them, U 11 represents the first real voltage value corresponding to the digitized target first real voltage signal, U 12 represents the first imaginary voltage value corresponding to the digitized target first imaginary voltage signal, U 21 represents the second real voltage value corresponding to the digitized target second real voltage signal, U 22 represents the second imaginary voltage value corresponding to the digitized target second imaginary voltage signal;

[0185] The absolute value of Z is calculated as:

[0186]

[0187] According to the digitized target first real voltage signal, target first imaginary voltage signal, target second real voltage signal and target second imaginary voltage signal, the loss factor of the fuel level sensor is obtained; the calculation formula of the loss factor is:

[0188]

[0189] Where D represents the loss factor;

[0190] According to the loss factor of the oil level sensor, the quality factor of the oil level sensor is obtained; the calculation formula of the quality factor is:

[0191] Q = 1 / D,

[0192] Here, Q represents the quality factor.

[0193] It should be noted that the loss factor is used to measure the ineffectiveness of the capacitor, and the loss factor is defined as the ratio of the loss energy of the capacitor to the stored energy. The lower the loss factor, the smaller the energy loss of the capacitor and the stronger the energy storage capacity. The quality factor is the opposite. This embodiment can judge the performance of the oil level sensor based on the loss factor and the quality factor.

[0194] In some embodiments, after obtaining the capacitance value of the oil level sensor, the capacitance measurement method based on the oil level sensor further includes:

[0195] If the capacitance value is less than zero, obtain the total impedance of the circuit;

[0196] If the total impedance of the circuit is less than the lower threshold, the circuit is in a short circuit state;

[0197] If the total circuit impedance is greater than the upper threshold, the circuit is in an open circuit state.

[0198] Specifically, the total circuit impedance can be calculated based on the series equivalent resistance and capacitance of the fuel level sensor, and the specific calculation process can refer to the above calculation formula. The lower threshold can be 100Ω, and the upper threshold can be 100kΩ.

[0199] Specifically, the control module 500 may perform a BIT (built-in self-test) according to the capacitance value and the total impedance of the circuit.

[0200] The advantage of this embodiment is that it can measure other parameters of the fuel level sensor in addition to the capacitance value, such as the series equivalent resistance of the fuel level sensor; the control module 500 can determine the circuit state (including short circuit or open circuit) based on the capacitance value and the total impedance of the circuit. Therefore, this embodiment can timely discover the faults in the circuit and improve the reliability and safety of the circuit.

[0201] In some embodiments, after obtaining the capacitance value of the fuel level sensor according to the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal, the capacitance measurement method based on the fuel level sensor further includes:

[0202] Obtain the capacitance value measured under a preset oil volume;

[0203] The circuit measurement deviation is calculated based on the reference capacitance value of the oil level sensor and the measured capacitance value; wherein the reference capacitance value is used to indicate the capacitance value of the oil level sensor at a preset oil level;

[0204] The control module is calibrated based on the circuit measurement deviation.

[0205] For example, there are 6 oil level sensors, and the reference capacitance value of each oil level sensor under the preset oil level is 50Ω, while the calculated capacitance values ​​are 52Ω, 52Ω, 51Ω, 52Ω, 53Ω and 52Ω respectively. The average difference is calculated based on these 6 capacitance values ​​and the reference capacitance value, and the average difference is used as the circuit measurement deviation. The circuit measurement deviation is 2, which is equivalent to the capacitance value measured by the capacitance measurement circuit based on the oil level sensor being 2Ω greater than the reference capacitance value. The control module is calibrated by the average difference to reduce the calculation error.

[0206] An embodiment of the present application further provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the above-mentioned capacitance measurement method based on the oil level sensor is implemented.

[0207] The memory, as a non-transient computer-readable storage medium, can be used to store non-transient software programs and non-transient computer executable programs. In addition, the memory may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some embodiments, the memory may optionally include a memory remotely disposed relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0208] The embodiments described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present application and do not constitute a limitation on the technical solutions provided in the embodiments of the present application. Those skilled in the art will appreciate that with the evolution of technology and the emergence of new application scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0209] Those skilled in the art will appreciate that the technical solutions shown in the figures do not constitute a limitation on the embodiments of the present application, and may include more or fewer steps than shown in the figures, or a combination of certain steps, or different steps.

[0210] The device embodiments described above are merely illustrative, and the units described as separate components may or may not be physically separated, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0211] Those skilled in the art will appreciate that all or some of the steps in the methods disclosed above, and the functional modules / units in the systems and devices may be implemented as software, firmware, hardware, or a suitable combination thereof.

[0212] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0213] The units described above 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 on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0214] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0215] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including multiple instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of various embodiments of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory, referred to as ROM), random access memory (Random Access Memory, referred to as RAM), disk or optical disk and other media that can store programs.

[0216] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but the scope of the rights of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by a person skilled in the art without departing from the scope and essence of the present invention should be within the scope of the rights of the present invention.

Claims

1. A capacitance measurement circuit based on an oil level sensor, characterized in that: include: Signal generating module, flow-pressure conversion module, phase-sensitive detection module, analog-to-digital conversion module and control module; The signal generating module is electrically connected to the oil level sensor, and is used to generate a first square wave signal, a second square wave signal and a sine wave excitation signal, so that the oil level sensor generates a feedback signal according to the sine wave excitation signal; wherein the first square wave signal and the second square wave signal have the same frequency and a phase difference of 90 degrees; The flow-pressure conversion module is electrically connected to the oil level sensor, and is used to obtain a first voltage signal according to the feedback signal, and to obtain a second voltage signal according to the sinusoidal wave excitation signal and the feedback signal; The phase-sensitive detection module is electrically connected to the signal generating module and the current-pressure conversion module, and the phase-sensitive detection module is used to obtain a target first real voltage signal according to the first voltage signal and the first square wave signal, obtain a target first imaginary voltage signal according to the first voltage signal and the second square wave signal, obtain a target second real voltage signal according to the second voltage signal and the first square wave signal, and obtain a target second imaginary voltage signal according to the second voltage signal and the second square wave signal; The analog-to-digital conversion module is electrically connected to the phase-sensitive detection module, and the analog-to-digital conversion module is used to digitize the target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal; The control module is electrically connected to the analog-to-digital conversion module, and is used to obtain the capacitance value of the oil level sensor based on the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal and the target second imaginary voltage signal.

2. The capacitance measurement circuit based on the oil level sensor according to claim 1, characterized in that: The capacitance measurement circuit based on the oil level sensor also includes: A time-sharing excitation module, the time-sharing excitation module is electrically connected to the signal generating module, the flow-pressure conversion module and the control module; wherein the signal generating module is connected to the oil level sensor through the time-sharing excitation module, and the flow-pressure conversion module is connected to the oil level sensor through the time-sharing excitation module; the time-sharing excitation module is used to electrically connect one of the multiple oil level sensors in response to the selection instruction of the control module, so that the selected oil level sensor generates the feedback signal according to the sinusoidal wave excitation signal.

3. The capacitance measurement circuit based on the oil level sensor according to claim 2 is characterized in that: The signal generation module includes: a signal source submodule, a signal filtering submodule, a comparison submodule, a zero calibration submodule and an amplification submodule; The signal source submodule is electrically connected to the control module, and the signal source submodule is used to generate a first initial sine wave signal, a second initial sine wave signal and a third initial sine wave signal in response to a control instruction of the control module; wherein the first initial sine wave signal, the second initial sine wave signal and the third initial sine wave signal have the same frequency, and the phase difference between the first initial sine wave signal and the second initial sine wave signal is 90 degrees; The signal filtering submodule is electrically connected to the signal source submodule, and the signal filtering submodule is used to filter the first initial sinusoidal wave signal to output a first AC sinusoidal wave signal, filter the second initial sinusoidal wave signal to output a second AC sinusoidal wave signal, and filter the third initial sinusoidal wave signal to output a third AC sinusoidal wave signal; The comparison submodule is electrically connected to the signal filtering submodule, and the comparison submodule is used to output the first square wave signal according to the first AC sine wave signal, and output the second square wave signal according to the second AC sine wave signal; The zero calibration submodule is electrically connected to the signal filtering submodule, and the zero calibration submodule is used to output a standard sine wave signal according to the third AC sine wave signal; wherein the standard sine wave signal is a sine wave signal with an initial phase of zero; The amplifying submodule is electrically connected to the zero-calibrating submodule, and the amplifying submodule is used to amplify the standard sine wave signal and output the sine wave excitation signal.

4. The capacitance measurement circuit based on the oil level sensor according to claim 3 is characterized in that: The time-sharing excitation module includes: an excitation end switch submodule and a feedback end switch submodule; The excitation end switch submodule is electrically connected to the amplifier submodule, the excitation end switch submodule has a first number of output ports, the feedback end switch submodule has a first number of input ports, one interface of each of the oil level sensors is electrically connected to one of the output ports of the excitation end switch submodule, and another interface of each of the oil level sensors is electrically connected to one of the input ports of the feedback end switch submodule; The excitation end switch submodule is used to select the output port in response to the gating instruction of the control module, and the feedback end switch submodule is used to select the input port in response to the gating instruction of the control module, so that the oil level sensor corresponding to the output port and the input port generates the feedback signal according to the sinusoidal wave excitation signal.

5. The capacitance measurement circuit based on the oil level sensor according to claim 4, characterized in that: The feedback signal includes a current feedback sub-signal and a voltage feedback sub-signal, and the current-voltage conversion module includes: a feedback end conditioning sub-module and an excitation end conditioning sub-module; The feedback-end conditioning submodule is electrically connected to the feedback-end switch submodule, and the feedback-end conditioning submodule is used to obtain the first voltage signal according to the current feedback sub-signal and the voltage feedback sub-signal; The excitation end conditioning submodule is electrically connected to the excitation end switch submodule and the feedback end switch submodule, and the excitation end conditioning submodule is used to obtain the second voltage signal according to the sinusoidal wave excitation signal and the voltage feedback subsignal.

6. The capacitance measurement circuit based on the oil level sensor according to claim 5, characterized in that: The phase-sensitive detection module includes: a waveform synthesis submodule and a low-pass filtering submodule; The waveform synthesis submodule is electrically connected to the comparison submodule, the feedback end conditioning submodule and the excitation end conditioning submodule, and the waveform synthesis submodule is used to perform waveform synthesis according to the first voltage signal and the first square wave signal to obtain an initial first real voltage signal, perform waveform synthesis according to the first voltage signal and the second square wave signal to obtain an initial first imaginary voltage signal, perform waveform synthesis according to the second voltage signal and the first square wave signal to obtain an initial second real voltage signal, and perform waveform synthesis according to the second voltage signal and the second square wave signal to obtain an initial second imaginary voltage signal; The low-pass filtering submodule is electrically connected to the waveform synthesis submodule, and is used to filter the initial first real voltage signal to obtain the target first real voltage signal, filter the initial first imaginary voltage signal to obtain the target first imaginary voltage signal, filter the initial second real voltage signal to obtain the target second real voltage signal, and filter the initial second imaginary voltage signal to obtain the target second imaginary voltage signal.

7. An aircraft, characterized in that: The invention comprises a capacitance measurement circuit based on an oil level sensor as described in any one of claims 1 to 6.

8. A capacitance measurement method based on an oil level sensor, characterized in that: The method is applied to a control module in a capacitance measurement circuit based on an oil level sensor according to any one of claims 1 to 6, and the method comprises: Obtaining a capacitance value of the oil level sensor according to the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal; The oil amount is determined according to the capacitance value.

9. The capacitance measurement method based on the oil level sensor according to claim 8, characterized in that: After obtaining the capacitance value of the oil level sensor according to the digitized target first real voltage signal, the target first imaginary voltage signal, the target second real voltage signal, and the target second imaginary voltage signal, the method further includes: The capacitance value is calculated as follows: Among them, U 11 represents the first real voltage value corresponding to the digitized target first real voltage signal, U 12 represents the first imaginary voltage value corresponding to the digitized target first imaginary voltage signal, U 21 represents the second real voltage value corresponding to the digitized target second real voltage signal, U 22 represents the second imaginary voltage value corresponding to the digitized target second imaginary voltage signal, f represents the frequency of the sinusoidal wave excitation signal, and C represents the capacitance value.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the capacitance measurement method based on the oil level sensor according to any one of claims 8 to 9 is implemented.

Images