Liquid level sensor and liquid level measuring method

Abstract

The invention provides a liquid level sensor and a liquid level measuring method, and relates to the technical field of sensors. The liquid level sensor comprises a detection capacitor, a signal processing board and a data communication port, the detection capacitor is connected with the signal processing board through a wire. The signal processing board is in communication connection with the data communication port; the signal processing board is used for responding to the liquid level measurement request through the data communication port, measuring capacitance by measuring charging and discharging time, obtaining the capacitance value of the current liquid level based on the detected capacitance, preprocessing the capacitance value, determining the liquid level value based on the preprocessed capacitance value and sending the liquid level value to external equipment through the data communication port; wherein the capacitance value is an analog signal; the liquid level value is a digital signal; the signal processing board is arranged in the liquid level sensor, capacitance signals of analog signals are converted into liquid level values of digital signals, then the liquid level values are output through the data communication port, long-distance transmission of the capacitance signals prone to electromagnetic interference is avoided through high-frequency charging and discharging measurement capacitance and the whole design, and the measurement precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to a liquid level sensor and a liquid level measuring method. Background Art

[0002] The existing capacitive liquid level sensor measures the capacitance signal of the capacitor inserted into the liquid to be tested, and transmits it to the comprehensive diagnostic device through the signal transmission cable. The comprehensive diagnostic device completes the final oil level value calculation. In some traditional typical capacitive liquid level sensors, a dielectric constant compensation sensor is also added. The dielectric constant compensation sensor is located at the bottom of the oil level sensor and is used to sense the change in the dielectric constant of the lubricating oil when the oil state changes. The signal of the dielectric constant compensation sensor is also transmitted to the comprehensive diagnostic device through the signal transmission cable. However, the sensor outputs a capacitance signal, which is easily affected by the parasitic capacitance caused by the transmission cable and its layout, and is easily affected by external electromagnetic interference. Summary of the invention

[0003] The object of the present invention is to provide a liquid level sensor and a liquid level measurement method. A signal processing board is set in the liquid level sensor, the size of the capacitor is measured according to the charging and discharging time, and the capacitance signal of the analog signal is converted into a liquid level value of a digital signal, which is then output through a data communication port. The high-frequency charging and discharging measurement capacitor and the entire design avoid the long-distance transmission of the capacitance signal that is susceptible to electromagnetic interference, thereby improving the measurement accuracy.

[0004] In a first aspect, the present invention provides a liquid level sensor, comprising: a detection capacitor, a signal processing board and a data communication port; The detection capacitor is connected to the signal processing board through a communication wire; The signal processing board is connected to the data communication port for communication; The signal processing board is used to respond to the liquid level measurement request through the data communication port, obtain the capacitance value of the current liquid level based on the detection capacitor, pre-process the capacitance value, determine the liquid level value based on the pre-processed capacitance value, and send the liquid level value to the external device through the data communication port; wherein the capacitance value is an analog signal; and the liquid level value is a digital signal.

[0005] In some preferred embodiments of the present invention, the detection capacitor comprises: a first electrode and a second electrode coaxially nested; a non-metallic material is filled between the first electrode and the second electrode; A first electrode sheet is disposed on the first electrode; A second electrode sheet is disposed on the second pole; The first electrode sheet is arranged opposite to the second electrode sheet.

[0006] In some preferred embodiments of the present invention, a plurality of first equivalent capacitance segments of equal length are arranged on the first electrode; the first electrode sheet is arranged on the first equivalent capacitance segment; A plurality of second equivalent capacitance segments of equal length are arranged on the second electrode; the second electrode sheet is arranged on the second equivalent capacitance segment; The first equivalent capacitance section is arranged opposite to the second equivalent capacitance section.

[0007] In some preferred embodiments of the present invention, the signal processing board includes: a capacitance reading unit; The signal processing board responds to the liquid level measurement request and obtains the discharge time of the detection capacitor; The capacitance reading unit determines the capacitance value based on the discharge time.

[0008] In some preferred embodiments of the present invention, the signal processing board further comprises: a compensation unit; the compensation unit comprises: a temperature-sensitive resistor; the preprocessing comprises: temperature compensation; The compensation unit performs temperature compensation on the capacitance value based on the ambient temperature obtained by the thermistor.

[0009] In some preferred embodiments of the present invention, the signal processing board further comprises: a filtering unit; the pre-processing further comprises: filtering processing; After the signal processing board obtains multiple capacitance values ​​of the current liquid level based on the detection capacitor, the filtering unit performs filtering processing on the multiple capacitance values.

[0010] In some preferred embodiments of the present invention, the signal processing board further comprises: an average value processing unit; the preprocessing further comprises: average value calculation; The average value processing unit calculates the average value of the remaining capacitance value after the filtering process to obtain an average capacitance value.

[0011] In some preferred embodiments of the present invention, the signal processing board is used to determine the liquid level value corresponding to the average capacitance value in a preset fitted capacitance-liquid level relationship diagram.

[0012] In some preferred embodiments of the present invention, the capacitance-liquid level relationship diagram is determined based on fitting of the zero value and the full value of the liquid level sensor.

[0013] In a second aspect, the present invention provides a liquid level measurement method, which is applied to the liquid level sensor provided in the first aspect, comprising: Respond to level measurement requests; A capacitance value is obtained based on the detected capacitance, the capacitance value is preprocessed, a liquid level value is determined based on the preprocessed capacitance value, and the liquid level value is output.

[0014] The present invention brings the following beneficial effects: The invention provides a liquid level sensor and a liquid level measurement method. The liquid level sensor comprises: a detection capacitor, a signal processing board and a data communication port; the detection capacitor is connected to the signal processing board through a communication wire; the signal processing board is communicatively connected to the data communication port; the signal processing board is used to respond to a liquid level measurement request through the data communication port, measure the size of the capacitor according to the charge and discharge time, obtain the capacitance value of the current liquid level based on the detection capacitor, pre-process the capacitance value, determine the liquid level value based on the pre-processed capacitance value, and send the liquid level value to an external device through the data communication port; wherein the capacitance value is an analog signal; the liquid level value is a digital signal; a signal processing board is arranged in the liquid level sensor, the capacitance signal of the analog signal is converted into the liquid level value of the digital signal, and then output through the data communication port, high-frequency charge and discharge measurement and the entire design avoid the long-distance transmission of the capacitance signal susceptible to electromagnetic interference, and improve the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a structural schematic diagram of a capacitive oil level compensation sensor in the prior art; Figure 2 A schematic diagram of the structure of a liquid level sensor provided by an embodiment of the present invention; Figure 3 An internal schematic diagram of a capacitance value chip provided by an embodiment of the present invention; Figure 4 A schematic diagram of a first capacitance measurement circuit is provided for an embodiment of the present invention; Figure 5 A schematic diagram of a signal conversion circuit provided by an embodiment of the present invention; Figure 6 A flow chart of a liquid level measurement method provided by an embodiment of the present invention.

[0017] Icons: 1-compensating middle tube; 2-compensating inner tube; 3-traditional inner tube; 4-traditional outer tube; 5-socket; 6-first inner tube; 7-new outer tube; 8-second inner tube; 9-support block; 10-mounting flange; 11-signal processing board; 12-data communication port. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0021] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0022] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0023] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] See also Figure 1The structure diagram of a capacitive oil level compensation sensor in the prior art is shown. The oil level compensation sensor is functionally divided into an oil level sensor and a dielectric constant compensation sensor. The sensor includes: a traditional inner tube 3 and a traditional outer tube 4, and the compensation sensor includes: a compensation middle tube 1 and a compensation inner tube 2. The oil level sensor is a coaxial capacitor, which is used to measure the oil level height signal in the lubricating oil tank; in order to ensure the accuracy of the capacitance measurement, a dielectric constant compensation sensor is added to the bottom of the liquid level sensor. The dielectric constant compensation sensor is located at the bottom of the oil level sensor and is used to sense the change in the dielectric constant of the lubricating oil when the oil state changes. The oil level compensation sensor outputs two capacitance signals, namely, the capacitance signal C output by the oil level sensor and the capacitance signal C0 output by the dielectric constant compensation sensor. The two sets of capacitance signals are transmitted to the comprehensive diagnostic device through the signal transmission cable, and the comprehensive diagnostic device completes the final oil level value calculation and outputs the result through the socket 5. However, the sensor outputs a capacitance signal, which is easily affected by the parasitic capacitance caused by the transmission cable and its layout, and is easily affected by external electromagnetic interference.

[0025] Driven by user structural requirements, it is necessary to solve the problems that the capacitance signal output by the capacitive liquid level sensor is easily interfered, the capacitance signal transmission has high requirements for cables, and the temperature affects the measurement accuracy of the capacitive liquid level sensor. Due to the original structure, the sensor itself only generates capacitance signals, and it is difficult to solve the problems of parasitic capacitance, capacitance signal interference and temperature, and it is difficult to achieve high-precision and accurate measurement under temperature changes.

[0026] To solve this problem, the signal acquisition component is integrated into the product. The capacitance signal is directly collected through the capacitance value chip, and after automatic compensation calculation, it is transmitted to the MCU. The MCU processes the capacitance signal into liquid level height and converts it into a digital signal output. The sensor has high measurement accuracy and the signal is not easily interfered with.

[0027] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0028] Embodiment 1 The present invention provides a liquid level sensor, comprising: a detection capacitor, a signal processing board 11 and a data communication port 12; the detection capacitor is connected to the signal processing board 11 through a communication wire; the signal processing board 11 and the data communication port 12 are communicatively connected; the signal processing board 11 is used to respond to a liquid level measurement request through the data communication port 12, obtain a capacitance value of a current liquid level based on the detection capacitor, pre-process the capacitance value, determine a liquid level value based on the pre-processed capacitance value, and send the liquid level value to an external device through the data communication port 12; wherein the capacitance value is an analog signal; and the liquid level value is a digital signal.

[0029] Specifically, the detection capacitor operates stably in the liquid medium and is not significantly affected by external environmental factors such as temperature, humidity, pressure, etc. In some preferred embodiments of the present invention, see Figure 2 The structural schematic diagram of a liquid level sensor provided by an embodiment of the present invention is shown, and the detection capacitor includes: a first pole (new outer tube 7) and a second pole (first inner tube 6 and second inner tube 8) coaxially nested, and the first inner tube 6 and the second inner tube 8 respectively form two capacitors with the outer tube. This is a structural design, and can be connected as needed, especially when the measurement height is very large and it is difficult to ensure the processing accuracy of the tube; non-metallic materials are filled between the first pole and the second pole; a first electrode sheet is arranged on the first pole; a second electrode sheet is arranged on the second pole; the first electrode sheet and the second electrode sheet are arranged opposite to each other.

[0030] Specifically, the inner tube and the outer tube are separated by non-metallic materials, and the outer tube is separated from the mounting flange 10 by non-metallic materials to achieve insulation. The inner tube and the outer tube constitute a coaxial capacitor, and the distance between the inner and outer tubes can be changed according to needs during the design stage to adjust the size of the basic capacitance value, and the capacitance value changes linearly with the change of the liquid level height. The two poles of the capacitor are connected to the signal processing board 11 through a shorter wire, which greatly reduces the error caused by parasitic capacitance brought by the capacitance signal transmission, and the capacitance value chip processes and compensates the capacitance signal. In some preferred embodiments of the present invention, the length of the wire is less than 100 mm.

[0031] A special coaxial capacitor design is adopted, in which the inner and outer electrodes are separated by a high-precision insulating material to form a uniform electric field distribution to reduce edge effects and improve measurement accuracy. In order to improve the sensitivity of the detection capacitor to liquid level changes, we optimize the surface area of ​​the electrodes and the distance between them to ensure a highly linear relationship between the capacitance change and the liquid level change. In addition, by selecting materials with low dielectric absorption and long-term stability, the reliability and accuracy of the sensor in long-term operation are ensured.

[0032] The signal processing board 11 is a key component that connects the detection capacitor and the data communication port 12. It first converts the analog capacitance value obtained by the detection capacitor into a digital signal. This process uses a high-precision analog-to-digital converter (ADC) to ensure the accuracy of the conversion. Then, these digital signals are sent to a microprocessor or microcontroller for preprocessing, including filtering, denoising and averaging to extract the real liquid level signal. In addition, the signal processing board 11 is also responsible for more complex data processing, such as compensating for the influence of temperature, because temperature changes may affect the capacitance value. The system we designed can monitor the ambient temperature in real time and adjust the capacitance value according to the preset temperature compensation algorithm to ensure the accuracy of measurement at different temperatures.

[0033] Furthermore, the signal processing board 11 may include: a microcontroller unit, an analog-to-digital converter, a power management module, and a signal conditioning circuit, etc.; the microcontroller unit is the "brain" of the signal processing board 11, responsible for controlling the entire data processing process, and an industrial-grade MCU with low power consumption, high processing power, and sufficient memory may be selected to ensure that data can be processed efficiently and complex algorithms can be run; the analog-to-digital converter is responsible for converting the analog signal output by the detection capacitor into a digital form for processing by the MCU, and the resolution and sampling rate of the ADC are key parameters to ensure that subtle capacitance changes can be captured and a rapid response can be achieved; the power management module is used to provide a stable power supply to all components on the board, including a voltage regulator, a decoupling capacitor, and a battery management system when necessary, to ensure that the onboard equipment can operate stably under different operating conditions; the signal conditioning circuit includes filters and amplifiers for optimizing the signal transmitted from the detection capacitor, and these circuits help to improve the signal-to-noise ratio, thereby improving the measurement accuracy of the entire system.

[0034] The data communication port 12 is designed to conveniently transfer processed data from the microprocessor to an external device or network. The present design supports a variety of communication protocols, including but not limited to I²C, SPI, UART, etc., to meet different hardware interface requirements. In some preferred embodiments of the present invention, the communication port can not only realize wired communication, but also support wireless data transmission through an integrated wireless module, which greatly expands the application range of the sensor. Through these communication ports, users can remotely monitor liquid level data in real time, and can also remotely configure sensor parameters or update its firmware. The design of the data communication port 12 takes security and reliability into consideration, and adopts data encryption and error checking mechanisms to ensure the security and accuracy of transmission.

[0035] The oil level sensor converts the liquid level into capacitance, and then extracts the analog signal through the capacitance measurement circuit. Figure 3 The internal principle diagram of a capacitance value chip provided by an embodiment of the present invention is shown. The chip is a capacitance digital conversion single chip solution with a single-chip microcomputer processing unit for dedicated capacitance measurement. Its front-end conversion unit is based on the principle of capacitance measurement based on discharge time. This conversion measurement principle provides high-precision time conversion with a minimum conversion time range of 2μs. The chip has a 48-bit DSP unit inside. This processing unit will process the capacitance measurement information, obtain the measurement data, and send the result to the chip output port. The MCU uses an 8MHz resonator for clocking and a 3V3 voltage for power supply. The SPI interface is used to receive the capacitance data collected by the capacitance acquisition chip.

[0036] Furthermore, in some preferred embodiments of the present invention, a plurality of first equivalent capacitor segments of equal length are arranged on the first electrode; the first electrode sheet is arranged on the first equivalent capacitor segment; a plurality of second equivalent capacitor segments of equal length are arranged on the second electrode; the second electrode sheet is arranged on the second equivalent capacitor segment; the first equivalent capacitor segment and the second equivalent capacitor segment are arranged opposite to each other.

[0037] Specifically, according to the capacitance value of the capacitance sensor, a suitable capacitor is selected as the reference capacitor. PC1, PC2, PC3, PC4, and PC5 are connected to each sub-capacitor of the sensor. PC1-PC5 are structural sub-capacitors. The number of connections is selected according to the needs. Multiple sub-capacitors share the outer tube. Non-metallic materials are selected on the inner tube to make the support block 9 for internal support. The outer wall of the non-metallic structure is pasted with five separated copper foil tapes for physical insulation, and connected to the circuit board through internal leads. The values ​​of the five sub-capacitors are processed separately as a liquid level (five sections, i.e., 20% each), and then the sum of each section is the total liquid level height. The empty values ​​of all sub-capacitors of the sensor are taken as 0 values, and the full oil values ​​of all capacitors are taken as full values. If a certain capacitor is completely immersed in the liquid surface, it is recorded as 20%, and if it is completely in the air, it is 0%. The amount of immersion is calculated in sections, and each section is a linear relationship. The sum of each section is the final oil volume. For capacitance value chips, the capacitance measurement registers are configured and read through the standard firmware of the chip in pc0-pc5, and the measured capacitance value is converted into a digital value with an accuracy of up to 21 effective bits. The capacitance value to be measured is calculated by reading the ratio C / C0 of the capacitance to be measured and the reference capacitance in the register. The measurable range covers several fF to several hundred nF. The capacitance sensor data can be calibrated inside the chip and then transmitted through the SPI or I2C data serial interface.

[0038] Furthermore, in some preferred embodiments of the present invention, the signal processing board 11 includes: a capacitance reading unit; the signal processing board 11 responds to the liquid level measurement request and obtains the discharge time of the detection capacitor; the capacitance reading unit determines the capacitance value based on the discharge time.

[0039] For details, see Figure 4 The embodiment of the present invention shown in the figure provides a schematic diagram of a first capacitance measurement circuit and Figure 5The schematic diagram of a signal conversion circuit provided by an embodiment of the present invention is shown in the figure below. The circuit design of the liquid level conversion of the capacitance reading module is shown in the figure below. BUFFCAP is connected to the ground to decouple the capacitor of Uf level, IIC is grounded and pulls down the pin to enable SPI, MISO_SDA is the SPI communication line, and there is also a crystal oscillator inside the chip. If an external crystal oscillator needs to be connected, it can be achieved through OXIN and OXOUT. PC0-PC7 are capacitance detection pins, and the appropriate connection method is selected as needed. PCAUX is used for an external pressure relief resistor. The PT2REF pin is used for an external reference resistor, and PTOUT is used to ground the pin through a capacitor when measuring temperature. SCK_SCL is the clock line of SPI, and SSN_PG0 is connected to the chip select signal line of SPI. Pulling it low means that the chip is selected. VDD is connected to the input voltage of 3.3V. VPP_OTP is grounded to pull down the voltage.

[0040] The sensor structure design ensures high linearity and produces high-precision capacitance; the capacitance acquisition circuit calculates the capacitance based on the principle of the value conversion chip and the "measurement of charge and discharge time". In order to improve the measurement accuracy, a single sensor drift mode is adopted. Set the configuration register to the ground mode and select the trigger source of the capacitance measurement as the continuous trigger mode. The program design of the high-precision oil level sensor mainly includes two parts, one is the configuration of the capacitance value chip and the program of the capacitance reading module, and the other is the program of the liquid level height conversion module of the single-chip microcomputer. For multiple capacitors connected to the chip, the discharge time of each capacitor will be uploaded to the MCU, and the first capacitor will be used as a reference comparison capacitor. After receiving the data, the MCU will compare the discharge time of the following capacitors with the discharge time of the first capacitor. Since the capacitance of the first capacitor is known and the discharge time is proportional to the capacitance value, the capacitance of the remaining measured capacitors can be solved by this method.

[0041] The measurement results can be derived using the following formula. The discharge time is proportional to the capacitance of the fuel level sensor and the reference capacitor: ; in, For the The discharge time of each capacitor is is the discharge time of the first sub-capacitor, For the The capacitance value of each capacitor is is the capacitance value of the first sub-capacitor.

[0042] Furthermore, in some preferred embodiments of the present invention, the signal processing board 11 also includes: a compensation unit; the compensation unit includes: a thermistor; the preprocessing includes: temperature compensation; the compensation unit performs temperature compensation on the capacitance value based on the ambient temperature obtained by the thermistor.

[0043] For details, see Figure 3 The chip can compensate for the internal parasitic capacitance and the internal comparator delay, which can ensure the reliable operation and high-precision measurement of the sensor. At the same time, the chip has its own on-chip thermistor, which can measure the ambient temperature for temperature compensation, and the multi-channel measurement circuits can compensate each other for reference. The chip has two on-chip resistors that can be used to measure temperature. One of them is an aluminum resistor with a temperature coefficient of TK≈2800ppm / K, which can be used as a temperature sensor, and the other is a polysilicon resistor with a TK coefficient close to zero as a reference. By setting the parameters in the corresponding register, read R0 / R ref The proportional relationship of the resistors obtains temperature compensation.

[0044] Furthermore, in some preferred embodiments of the present invention, the signal processing board 11 also includes: a filtering unit; the preprocessing also includes: filtering processing; after the signal processing board 11 obtains multiple capacitance values ​​of the current liquid level based on the detection capacitor, the filtering unit performs filtering processing on the multiple capacitance values.

[0045] Furthermore, in some preferred embodiments of the present invention, the signal processing board 11 also includes: an average value processing unit; the preprocessing also includes: average value calculation; the average value processing unit calculates the average value of the remaining capacitance value after filtering to obtain an average capacitance value.

[0046] Specifically, since the chip can measure up to 2μs, it can perform multiple measurements in a very short time, remove and filter the sudden changes, obtain multiple relatively accurate calculation values ​​in a short time, and then average the multiple measurement values ​​to obtain a very stable capacitance value. At this time, the capacitance and liquid level will have a good linear relationship. The single-chip microcomputer removes abnormal data and filters the capacitance value, then performs multiple measurements to average the calculation, and then calculates based on the linear relationship between capacitance and liquid level.

[0047] Furthermore, in some preferred embodiments of the present invention, the signal processing board 11 is used to determine the liquid level value corresponding to the average capacitance value in a preset fitting capacitance-liquid level relationship diagram.

[0048] Furthermore, in some preferred embodiments of the present invention, the capacitance-liquid level relationship diagram is determined based on fitting of the zero value and full value of the liquid level sensor.

[0049] Specifically, in order to ensure the accuracy of the measured liquid level value, the sensor needs to be calibrated (zero and full). A fixed code is input through the communication interface to write a zero value when the oil is empty and a full value when the oil is full. The MCU calculates the capacitance value to calculate the liquid level with high precision and high linearity. Zero and full are achieved through the communication interface, and the capacitance values ​​of the empty and full liquid levels can be stored in advance. When the liquid level changes, the real-time capacitance value can be obtained, and the current liquid level is calculated by the difference in capacitance to achieve high-precision liquid level measurement. Finally, the liquid level is sent periodically through the communication interface.

[0050] The embodiment of the present invention provides a liquid level sensor, which uses a capacitance value chip and a single-chip microcomputer, making the oil level sensor more intelligent and miniaturized. The capacitance signal is directly processed into the liquid level height at the sensor end and converted into a digital signal output, which solves the problem that the capacitance signal and its transmission are susceptible to interference from the source. At the same time, the use of a capacitance value chip can directly perform temperature compensation on the capacitor from the chip, and by selecting a high-precision reference capacitor that is less affected by temperature, the influence of temperature drift on liquid level measurement is greatly reduced. In addition, calibration can be performed directly through the communication interface on the sensor, avoiding the influence of parasitic capacitance brought by external access equipment during the calibration process, and meeting the demand for high-precision liquid level measurement.

[0051] The present invention provides a liquid level sensor, comprising: a detection capacitor, a signal processing board 11 and a data communication port 12; the detection capacitor is connected to the signal processing board 11 through a communication wire; the signal processing board 11 and the data communication port 12 are communicatively connected; the signal processing board 11 is used to respond to a liquid level measurement request through the data communication port 12, obtain a capacitance value of a current liquid level based on the detection capacitor, pre-process the capacitance value, determine a liquid level value based on the pre-processed capacitance value, and send the liquid level value to an external device through the data communication port 12; wherein the capacitance value is an analog signal; the liquid level value is a digital signal; the signal processing board 11 is arranged in the liquid level sensor, the capacitance signal of the analog signal is converted into a liquid level value of a digital signal, and then output through the data communication port 12, thereby reducing electromagnetic interference and improving measurement accuracy.

[0052] The present invention provides a liquid level sensor, which measures the capacitance change caused by the liquid level through a capacitance value chip, and solves the liquid level through an MCU to output a digital signal, thereby solving the problem that analog signals such as output capacitance are easily interfered with. The capacitance change caused by the liquid level is measured through a capacitance value chip, and the liquid level is solved through an MCU, and the automatic compensation of the capacitance value chip and the compensation calibration of an external reference capacitor solve the problem of the influence of temperature drift on the measurement accuracy of the sensor, and at the same time solves the problem of inaccurate measurement of the compensation end of the traditional capacitive liquid level sensor.

[0053] Embodiment 2 On the basis of the above embodiment, an embodiment of the present invention provides a liquid level measurement method, which is applied to the liquid level sensor provided in the above embodiment. The method includes: Respond to the liquid level measurement request, obtain a capacitance value based on the detection capacitance, pre-process the capacitance value, determine the liquid level value based on the pre-processed capacitance value, and output the liquid level value.

[0054] For details, see Figure 6 The flowchart of a liquid level measurement method provided by an embodiment of the present invention shown in the figure includes the following specific steps: initializing the system; starting periodic acquisition; filtering the acquired capacitance value; judging whether calibration and storage are required; if so, executing storage of calibration values ​​before proceeding to the next step; if not, directly proceeding to the next step; judging whether calibration readings are required; if so, executing reading of calibration values ​​and then periodically sending liquid level information; if not, directly sending liquid level information periodically.

[0055] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the liquid level measurement method described above can refer to the corresponding liquid level sensor in the aforementioned method embodiment, and will not be repeated here.

[0056] In addition, in the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid level sensor, characterized in that: include: Detect capacitors, signal processing boards and data communication ports; The detection capacitor is connected to the signal processing board via a communication wire; The signal processing board is communicatively connected with the data communication port; The signal processing board is used to respond to the liquid level measurement request through the data communication port, obtain the capacitance value of the current liquid level based on the detection capacitor, pre-process the capacitance value, determine the liquid level value based on the pre-processed capacitance value, and send the liquid level value to the external device through the data communication port; wherein the capacitance value is an analog signal; and the liquid level value is a digital signal.

2. The liquid level sensor according to claim 1, characterized in that: The detection capacitor comprises: a first electrode and a second electrode coaxially nested; a non-metallic material is filled between the first electrode and the second electrode; A first electrode sheet is disposed on the first electrode; A second electrode sheet is disposed on the second electrode; The first electrode sheet is arranged opposite to the second electrode sheet.

3. The liquid level sensor according to claim 2, characterized in that: A plurality of first equivalent capacitance segments of equal length are arranged on the first electrode; the first electrode sheet is arranged on the first equivalent capacitance segment; A plurality of second equivalent capacitance segments of equal length are arranged on the second electrode; the second electrode sheet is arranged on the second equivalent capacitance segment; The first equivalent capacitance segment and the second equivalent capacitance segment are arranged opposite to each other.

4. The liquid level sensor according to claim 1, characterized in that: The signal processing board includes: a capacitance reading unit; The signal processing board responds to the liquid level measurement request to obtain the charging and discharging time of the detection capacitor; The capacitance reading unit determines the capacitance value based on the charge and discharge time and by comparing it with a high-precision reference capacitance.

5. The liquid level sensor according to claim 1, characterized in that: The signal processing board further comprises: a compensation unit; the compensation unit comprises: a temperature-sensitive resistor; the pre-processing comprises: temperature compensation; The compensation unit performs temperature compensation on the capacitance value based on the ambient temperature acquired by the temperature-sensitive resistor.

6. The liquid level sensor according to claim 5, characterized in that: The signal processing board further comprises: a filtering unit; the pre-processing further comprises: filtering processing; After the signal processing board obtains the multiple capacitance values ​​of the current liquid level based on the detection capacitor, the filtering unit performs the filtering process on the multiple capacitance values.

7. The liquid level sensor according to claim 6, characterized in that: The signal processing board further comprises: an average value processing unit; the preprocessing further comprises: average value calculation; The average value processing unit calculates the average value of the remaining capacitance value after the filtering process to obtain an average capacitance value.

8. The liquid level sensor according to claim 7, characterized in that: The signal processing board is used to determine the liquid level value corresponding to the average capacitance value in a preset fitting capacitance-liquid level relationship diagram.

9. The liquid level sensor according to claim 8, characterized in that: The capacitance-liquid-level relationship diagram is determined based on fitting of the zero value and the full value of the liquid level sensor.

10. A liquid level measurement method, characterized in that: The liquid level sensor according to any one of claims 1 to 9 comprises: Respond to level measurement requests; A capacitance value is obtained based on the detected capacitance, the capacitance value is preprocessed, a liquid level value is determined based on the preprocessed capacitance value, and the liquid level value is output.

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