Precise air pressure type electronic liquid level meter and detection method

Abstract

The invention belongs to the field of liquid level detection, and particularly relates to a precise air pressure type electronic liquid level meter and a detection method.The precise air pressure type electronic liquid level meter comprises a liquid level meter shell and a circuit board, the circuit board is arranged in the liquid level meter shell, a hardware part is arranged on the upper surface of the circuit board, and an interface wire harness is arranged on one side of the liquid level meter shell; the interface wire harness is connected with the circuit board through a connector, an air pipe hole is formed in the bottom of the liquid level meter shell, the hardware part comprises an electronic air pressure sensor arranged on the circuit board, the electronic air pressure sensor is used for converting air pressure changes into electric signal changes, and a pre-amplifier is arranged on one side of the electronic air pressure sensor. In a factory mode, an upper PC can be used for automatically and rapidly calibrating a product, the efficiency is high, a software anti-interference algorithm is built in MCU software, a measurement value is automatically corrected, various media can be measured, the measurement precision is high, and the application range is greatly widened through multi-interface output (when the media are water, the resolution ratio is smaller than mm); the method is widely applied to food chemical industry.

Description

Technical Field

[0001] The invention belongs to the field of liquid level detection, in particular to a precision air pressure type electronic liquid level meter and a detection method. Background Art

[0002] In the field of liquid level detection, there are currently mainly A pressure type liquid level gauges and B electronic capacitance liquid level gauges. A pressure type liquid level gauge converts pressure into electrical signals for measurement through the pressure diaphragm inside the probe, but it has many defects, high manufacturing cost and high installation requirements, large errors, and slow response to slight pressure changes, especially in low liquid level application scenarios with a small measurement limit. The error is more obvious. B electronic capacitance liquid level gauge measures by placing electrodes into the measured liquid and measuring based on changes in electrode capacitance caused by changes in liquid level. However, it also has significant disadvantages. When the electrode is immersed in the liquid, the electrode protective layer is easily damaged in high temperature and acid-base solutions, causing metal ions to mix into the solution, which will have an adverse effect in the food and chemical industry; and because the electrode requires a certain area to increase sensitivity, it is easily interfered in a complex electromagnetic environment, resulting in equipment unavailability or increased measurement errors.

[0003] The semiconductor pressure strain gauge in the traditional pneumatic electronic level gauge is restricted by the production process and inevitably produces errors. There will be output at 0 pressure, resulting in inaccurate measurement. Usually, hardware circuit adjustment is used to reduce errors, but this method is subject to human subjectivity. The adjustment result requires that the sensor and the conversion device must match. Once the sensor is replaced, it needs to be readjusted. The human adjustment efficiency is low and is not conducive to reducing product costs. In addition, its transmission signal is generally an analog signal or a frequency signal, which is susceptible to interference and inconvenient for system integration. When the measuring medium changes, the parameters of the circuit-related parts need to be readjusted, which is extremely inconvenient to use.

[0004] To this end, the present invention provides a precise air pressure type electronic liquid level gauge and a detection method. Summary of the invention

[0005] In order to make up for the deficiencies of the prior art, at least one technical problem raised in the background technology is solved.

[0006] The technical solution adopted by the present invention to solve its technical problem is: the precision pneumatic electronic liquid level gauge described in the present invention includes a liquid level gauge housing and a circuit board, the interior of the liquid level gauge housing is provided with a circuit board, the upper surface of the circuit board is provided with a hardware part, one side of the liquid level gauge housing is provided with an interface harness, the interface harness is connected to the circuit board through a connector, and an air pipe hole is opened at the bottom of the liquid level gauge housing.

[0007] Preferably, the hardware part includes an electronic air pressure sensor arranged on a circuit board, the electronic air pressure sensor is used to convert air pressure changes into electrical signal changes, a pre-amplifier is arranged on one side of the electronic air pressure sensor, the pre-amplifier is used to convert the electrical signal sent by the sensor that is too weak or too strong to a reasonable range, and a microprocessor is arranged on one side of the pre-amplifier, the microprocessor is used to quantify the signal sent by the pre-amplifier and perform corresponding operations according to the program algorithm to meet relevant requirements.

[0008] A precision pneumatic electronic liquid level gauge detection method, the detection method comprising the following steps:

[0009] S1, start, the starting point of the entire software process, marking the start of the operation of the precision pneumatic electronic liquid level meter and detection method software system;

[0010] S2. Determine whether it is engineering mode:

[0011] Engineering mode: This is a special working mode, mainly used for calibration and parameter setting maintenance of the level meter. When it is judged to be in engineering mode, the software will enter a specific processing flow.

[0012] Non-engineering mode: If it is not engineering mode, it will skip the specific operations related to engineering mode and directly enter the normal measurement and signal processing process;

[0013] S3. Read calibration correction parameters (non-engineering mode):

[0014] When in non-engineering mode, the software reads the previously saved calibration correction parameters from the storage device;

[0015] S4, analog-to-digital conversion, whether in engineering mode or not, the analog voltage signal output by the pre-amplifier needs to be converted into a digital signal through the analog-to-digital converter built into the microprocessor for subsequent digital signal processing;

[0016] S5, determining whether it is the engineering mode again, and determining the engineering mode again after the analog-to-digital conversion to determine the subsequent processing flow;

[0017] S6, signal processing (in non-engineering mode), in non-engineering mode, processing the digital signal after analog-to-digital conversion;

[0018] S7, host computer communication processing, whether in engineering mode or non-engineering mode, host computer communication processing is required;

[0019] S8, user IO processing, processing the IO interface according to the user's configuration and actual needs;

[0020] S9, output analog signal processing, converting the processed liquid level data into a standard analog signal output so as to connect and communicate with other analog input devices;

[0021] S10, calibration data calculation (in engineering mode), when in engineering mode, calibration data calculation is performed based on the read calibration correction parameters and current measurement data;

[0022] S11, saving calibration data (in engineering mode), saving the calculated calibration data to a storage device so that it can be read next time;

[0023] S12, host computer communication (in engineering mode). In engineering mode, in addition to calculating and saving calibration data, it is also necessary to communicate with the host computer to send relevant information in the calibration process to the host computer, and at the same time receive calibration instructions and parameter settings and other information sent by the host computer.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The precision pneumatic electronic liquid level gauge and detection method described in the present invention, through the design of automatic and rapid calibration using the host PC in factory mode, changes the traditional pneumatic electronic liquid level gauge's manual error adjustment method based on hardware circuits. The traditional method has problems such as human subjectivity, low adjustment efficiency, and the need for readjustment after sensor replacement. This solution greatly improves the calibration efficiency and reduces labor and time costs.

[0026] 2. The precision pneumatic electronic liquid level meter and detection method described in the present invention improves the shortcomings of existing liquid level meters (such as electronic capacitive liquid level meters that are easily interfered in complex electromagnetic environments, and traditional pneumatic electronic liquid level meters that transmit signals that are easily interfered with and inconvenient for system integration) that are susceptible to interference through the design of built-in software anti-interference algorithm in MCU software. It can automatically correct the measured value, ensure the stability and accuracy of the measurement, and can still work reliably in complex electromagnetic environments.

[0027] 3. The precision pneumatic electronic liquid level gauge and detection method described in the present invention, through the reasonable design of the hardware part and the calibration and correction function of the software, enables the liquid level gauge to measure a variety of media with high accuracy (the resolution is less than 1mm when the medium is water). Different from the existing pressure type liquid level gauges with large errors, slow response to slight pressure changes, and large errors in low liquid level applications, as well as the problem that the semiconductor pressure strain gauges of traditional pneumatic electronic liquid level gauges are prone to errors and lead to inaccurate measurements, this solution has achieved a significant improvement in measurement accuracy.

[0028] 4. The precision pneumatic electronic liquid level meter and detection method described in the present invention, by setting a design of multiple interface outputs (RS232 / 485, IO interface, analog output, etc.), greatly increases the scope of application compared to the relatively single interface of the existing liquid level meter. It is convenient to connect and communicate with a variety of devices, can meet the needs of different users and application scenarios, and can be widely used in food and chemical industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below in conjunction with the accompanying drawings.

[0030] Figure 1 It is the overall structural diagram of the present invention;

[0031] Figure 2 It is a cross-sectional view of the overall structure of the present invention;

[0032] Figure 3 It is a partial split structure diagram in the present invention;

[0033] Figure 4 It is a structural diagram of the extension component in the present invention;

[0034] Figure 5 This is a practical application diagram of the electronic liquid level meter in the present invention.

[0035] In the figure: 1. Liquid level meter housing; 2. Circuit board; 3. Electronic air pressure sensor; 4. Pre-amplifier; 5. Microprocessor; 6. Interface harness; 7. Air pipe hole. DETAILED DESCRIPTION

[0036] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0037] like Figures 1 to 4 As shown, the precision pneumatic electronic liquid level gauge of an embodiment of the present invention includes a liquid level gauge housing 1 and a circuit board 2. The circuit board 2 is arranged inside the liquid level gauge housing 1, and the upper surface of the circuit board 2 is provided with a hardware part. An interface harness 6 is arranged on one side of the liquid level gauge housing 1, and the interface harness 6 is connected to the circuit board 2 through a connector. An air pipe hole 7 is opened at the bottom of the liquid level gauge housing 1.

[0038] The hardware part includes an electronic air pressure sensor 3 arranged on a circuit board 2. The electronic air pressure sensor 3 is used to convert air pressure changes into electrical signal changes. A preamplifier 4 is arranged on one side of the electronic air pressure sensor 3. The preamplifier 4 is used to convert the electrical signal sent by the sensor that is too weak or too strong into a reasonable range. A microprocessor 5 is arranged on one side of the preamplifier 4. The microprocessor 5 is used to quantify the signal sent by the preamplifier 4 and perform corresponding operations according to the program algorithm to meet relevant requirements.

[0039] like Figures 1 to 3 As shown, an air pipe hole 7 is provided at the bottom of the liquid level gauge housing 1, and an air pressure conduit is inserted into the liquid level gauge through the air pipe hole 7. The air pressure conduit is used to transmit air pressure, and transmits the external air pressure to the air pressure sensor, and is a channel for transmitting air pressure signals;

[0040] The electronic air pressure sensor 3 is the core sensing component, which can convert the air pressure change, which can also be caused by the change of liquid level depth, into an electrical signal change, and outputs a voltage change of 0-10mV. The voltage change range of different sensors is different;

[0041] Pre-amplifier 4 processes the electrical signal from the air pressure sensor. If the signal is too weak or too strong, it will be converted to a reasonable range, that is, a voltage of 0-3.3V will be output to the MCU for AD sampling;

[0042] The microprocessor 5 quantizes the signal sent by the pre-amplifier 4, performs corresponding operations according to the program algorithm to meet relevant requirements, completes signal conversion such as IO signal, analog output and modbus, and can configure multiple interfaces such as RS232 / 485, IO interface, analog output, etc. according to different needs, which is convenient for users.

[0043] like Figure 4 As shown, the precision pneumatic electronic liquid level meter and detection method are composed of two parts: hardware and software. The composition and function of the hardware part are as mentioned above, and the software part includes MCU software and PC software:

[0044] MCU Software

[0045] Complete signal acquisition;

[0046] Complete relevant application logic to meet actual usage requirements;

[0047] Send out the processing results (IO mode: analog output or digital output; the existing digital output mode is modbus and can be changed according to actual needs);

[0048] Engineering mode, obtain error correction values ​​for accurate measurement in non-engineering mode.

[0049] The detailed description of the software flow chart steps is as follows:

[0050] S1. Start: The starting point of the entire software process, marking the start of the operation of the precision pneumatic electronic liquid level meter and detection method software system;

[0051] S2. Determine whether it is engineering mode:

[0052] Engineering mode: This is a special working mode, mainly used for maintenance operations such as calibration and parameter setting of the level meter. When it is judged to be in engineering mode, the software will enter a specific processing flow;

[0053] Non-engineering mode: If it is not engineering mode, skip the specific operations related to engineering mode and directly enter the normal measurement and signal processing process;

[0054] S3. Read calibration correction parameters (non-engineering mode):

[0055] When in non-engineering mode, the software reads the previously saved calibration correction parameters from the storage device (such as EEPROM, etc.). These parameters are used to correct the measurement errors caused by sensor manufacturing differences, environmental factors, etc., in order to improve the measurement accuracy of the level meter;

[0056] S4, analog-to-digital conversion, whether in engineering mode or not, the analog voltage signal (0-3.3V or 0-5V variable voltage) output by the preamplifier 4 needs to be converted into a digital signal through the analog-to-digital converter (ADC) built into the microprocessor 5 (MCU) for subsequent digital signal processing;

[0057] S5, determining whether it is the engineering mode again, and determining the engineering mode again after the analog-to-digital conversion to determine the subsequent processing flow;

[0058] S6. Signal processing (non-engineering mode): In non-engineering mode, the digital signal after analog-to-digital conversion is processed. This includes converting the digital signal into the corresponding liquid level value according to the measurement principle and algorithm of the liquid level meter, and performing filtering, smoothing and other processing to remove noise interference and improve the accuracy and stability of the measurement;

[0059] S7, host computer communication processing, whether in engineering mode or non-engineering mode, host computer communication processing is required. The software sends the processed liquid level data, equipment status information, etc. to the host computer (such as computer, PLC, etc.) through RS232 / 485 and other communication interfaces, and can also receive control instructions and parameter settings from the host computer;

[0060] S8, user IO processing, processes the IO interface according to the user's configuration and actual needs. For example, when the liquid level reaches the preset height, the switch signal is output through the IO interface to control external devices (such as valves, alarms, etc.); or the signal input by the external device through the IO interface is received to realize more complex control logic;

[0061] S9, output analog signal processing, converting the processed liquid level data into a standard analog signal (such as 4-20mA current signal or 0-10V voltage signal, etc.) for output, so as to connect and communicate with other analog input devices;

[0062] S10, calibration data calculation (in engineering mode), when in engineering mode, the calibration data is calculated based on the read calibration correction parameters and the current measurement data. This may include calibration and adjustment of the sensor's zero point, full scale, linearity and other parameters to ensure the measurement accuracy of the level meter;

[0063] S11. Save the calibration data (in engineering mode). Save the calculated calibration data to the storage device so that it can be read the next time it is used. This ensures that the level meter can maintain a high measurement accuracy in different working environments and time.

[0064] S12, host computer communication (in engineering mode). In engineering mode, in addition to calculating and saving calibration data, it is also necessary to communicate with the host computer to send relevant information in the calibration process (such as calibration progress, calibration results, etc.) to the host computer, and at the same time receive calibration instructions and parameter settings sent by the host computer.

[0065] PC Software

[0066] Electronic level connection;

[0067] Obtain relevant parameters of electronic air pressure sensor 3;

[0068] Automatic correction based on relevant correction parameters obtained from sensor parameters;

[0069] Set the relevant liquid level height corresponding to the IO signal;

[0070] Get sensor data in real time.

[0071] Practical application of electronic level meter Figure 5 As shown;

[0072] The working principle of the pneumatic electronic level gauge is as follows:

[0073] Liquid level changes will cause air pressure changes (because changes in liquid level depth can change the measured air pressure). The external air pressure is transmitted to the electronic air pressure sensor 3 through the air pipe hole 7 at the bottom of the liquid level meter shell and the air pressure conduit. As the core sensing component, the electronic air pressure sensor 3 converts air pressure changes into electrical signal changes and outputs a voltage of 0-10mV (the voltage change range of different sensors is different).

[0074] Since the electrical signal output by the sensor may be too weak or too strong, it needs to be processed by the pre-amplifier 4, converted to a reasonable voltage range of 0-3.3V, and then sent to the microprocessor 5 (MCU). The MCU quantizes the signal sent by the pre-amplifier 4, performs corresponding operations according to the program algorithm, and completes the signal conversion (such as IO signal, analog output, and modbus, etc.).

[0075] In terms of software, the MCU software first determines whether it is in engineering mode. If it is in engineering mode, the calibration correction parameters are obtained, and after analog-to-digital conversion, the engineering mode is determined again, and then the calibration data is calculated, the calibration data is saved, and the communication with the host computer is performed; if it is not in engineering mode, the signal processing is performed after analog-to-digital conversion, the calibration correction parameters are read, the calibration calculation is performed, the digital signal is converted into the corresponding liquid level height value, and then the host computer communication processing, user IO processing and output analog signal processing are performed. The PC software part can realize the functions of electronic liquid level connection, obtaining relevant parameters of electronic air pressure sensor 3, automatically correcting correction parameters, setting the liquid level height corresponding to the IO signal, and obtaining sensor data in real time. Finally, the processed signal is output through a variety of interfaces (RS232 / 485, IO interface, analog output, etc.), which is convenient for users to use and is widely used in food and chemical industries.

[0076] This pneumatic electronic level gauge can use the host PC to automatically and quickly calibrate the product in factory mode, with high efficiency. The MCU software has built-in software anti-interference algorithm, automatically corrects the measured value, can measure a variety of media, and has high measurement accuracy (resolution is less than 1mm when the medium is water). The multi-interface output greatly increases the scope of application; it is widely used in the food and chemical industry.

[0077] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A precision pneumatic electronic liquid level gauge, comprising a liquid level gauge housing (1) and a circuit board (2), characterized in that: A circuit board (2) is arranged inside the liquid level meter housing (1), a hardware part is arranged on the upper surface of the circuit board (2), an interface harness (6) is arranged on one side of the liquid level meter housing (1), the interface harness (6) is connected to the circuit board (2) via a connector, and an air pipe hole (7) is opened at the bottom of the liquid level meter housing (1).

2. The precision air pressure type electronic liquid level gauge according to claim 1 is characterized in that: The hardware part comprises an electronic air pressure sensor (3) arranged on a circuit board (2), the electronic air pressure sensor (3) being used to convert air pressure changes into electrical signal changes, a preamplifier (4) being arranged on one side of the electronic air pressure sensor (3), the preamplifier (4) being used to convert an electrical signal sent by the sensor that is too weak or too strong into a reasonable range, a microprocessor (5) being arranged on one side of the preamplifier (4), the microprocessor (5) being used to quantify the signal sent by the preamplifier (4) and perform corresponding operations according to a program algorithm to meet relevant requirements.

3. A method for detecting a precision air pressure type electronic liquid level gauge, using the precision air pressure type electronic liquid level gauge described in any one of claims 1 to 2 for detection, characterized in that: The detection method comprises the following steps: S1, start, the starting point of the entire software process, marking the start of the operation of the precision pneumatic electronic liquid level meter and detection method software system; S2. Determine whether it is engineering mode: Engineering mode: This is a special working mode, mainly used for calibration and parameter setting maintenance of the level meter. When it is judged to be in engineering mode, the software will enter a specific processing flow. Non-engineering mode: If it is not engineering mode, it will skip the specific operations related to engineering mode and directly enter the normal measurement and signal processing process; S3. Read calibration correction parameters (non-engineering mode): When in non-engineering mode, the software reads the previously saved calibration correction parameters from the storage device; S4, analog-to-digital conversion, whether in engineering mode or not, the analog voltage signal output by the preamplifier (4) needs to be converted into a digital signal through the analog-to-digital converter built into the microprocessor (5) for subsequent digital signal processing; S5, determining whether it is the engineering mode again, and determining the engineering mode again after the analog-to-digital conversion to determine the subsequent processing flow; S6, signal processing (in non-engineering mode), in non-engineering mode, processing the digital signal after analog-to-digital conversion; S7, host computer communication processing, whether in engineering mode or non-engineering mode, host computer communication processing is required; S8, user IO processing, processing the IO interface according to the user's configuration and actual needs; S9, output analog signal processing, converting the processed liquid level data into a standard analog signal output so as to connect and communicate with other analog input devices; S10, calibration data calculation (in engineering mode), when in engineering mode, calibration data calculation is performed based on the read calibration correction parameters and current measurement data; S11, saving calibration data (in engineering mode), saving the calculated calibration data to a storage device so that it can be read next time; S12, host computer communication (in engineering mode). In engineering mode, in addition to calculating and saving calibration data, it is also necessary to communicate with the host computer to send relevant information in the calibration process to the host computer, and at the same time receive calibration instructions and parameter settings and other information sent by the host computer.

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