Apple sugar detection system based on electrical impedance

Abstract

The utility model provides an electrical impedance-based apple sugar detection system, which comprises a master control and display module, an excitation signal generation module, a signal conditioning module, an amplitude-phase detection module, an A / D (analog / digital) conversion module and a power supply module, the main control and display module is electrically connected with the measuring electrode through the A / D conversion module, the amplitude-phase detection module, the signal conditioning module and the signal holding circuit in sequence; the main control and display module is also electrically connected with the excitation electrode through the excitation signal generation module, the band-pass filter and the voltage-controlled constant current source circuit in sequence; the measuring electrode and the exciting electrode are attached to the surface of the apple; the power supply module provides power for the system. The apple sugar detector can be used for detecting on the basis of ensuring the integrity of apples, is small in size, portable, wide in application scene and simple and convenient to operate, and can better meet the requirement of apple sugar detection.

Description

Technical Field

[0001] This utility model relates to a detection system, specifically an apple sugar content detection system based on electrical impedance. Background Technology

[0002] Apples, as one of the most popular fruits, enjoy the reputation of being the "King of Fruits." Apples are rich in sugars, acids, various vitamins, minerals, fiber, polyphenols, and flavonoids, and are considered a "comprehensive health fruit." With the improvement of living standards, people's focus when purchasing fruit has changed. Previously, they emphasized external qualities such as size, color, and shape, but now they place greater emphasis on internal qualities such as acidity, sugar content, taste, and nutritional quality such as vitamin and fiber content. Among these, sugar content is a crucial indicator affecting the taste and measuring the internal quality of fruit. Internationally, Fuji apples have strict harvesting standards; their sugar content must reach 16°Brix before harvesting. Japan and the United States are major Fuji apple-growing countries and have adopted this standard for harvesting. For fruit farmers, internal quality testing allows them to promptly understand the sugar content of the fruit, enabling them to rationally schedule harvesting and adjust lighting. For processors, it allows for precise grading based on internal quality during the post-harvest commercial processing, enhancing the competitiveness of their products. Therefore, rapid and efficient non-destructive testing technologies are particularly important.

[0003] Bioelectrical impedance is a physical quantity that reflects the electrical properties of biological tissues, organs, cells, or the entire organism. Bioelectrical impedance measurement technology is a detection technique that utilizes the electrical characteristics (impedance, admittance, dielectric constant, etc.) of biological tissues and organs and their changes to extract biomedical information related to the physiological and pathological conditions of the organism. This technology is non-invasive, inexpensive, safe, non-toxic, harmless, easy to operate, and provides rich information, thus having broad application prospects. The impedance spectrum characteristics of biological tissues mainly refer to the significant changes in the resistive and capacitive components of biological tissue impedance with different applied electrical signal frequencies. This patent innovatively proposes to study the impedance spectrum of apples based on this characteristic of biological tissues, exploring the relationship between the sugar content of apples and their impedance.

[0004] Existing fruit sugar content testing devices are mostly destructive. Chinese utility model patent CN219871274U discloses a portable fruit sugar content testing device. Its features include a conical seat, support frame, steel mesh, motor, limiting tube, lead screw, limiting post, and pressure plate. The lead screw is threadedly connected to the limiting post, and the limiting post is slidably connected to the limiting tube. Fruit tissue is then placed inside the steel mesh. The mounting base is threadedly connected to the top of the outer shell. The motor drives the lead screw and limiting post to rotate relative to each other, driving the pressure plate downwards to squeeze the fruit tissue. The fruit juice passes through the steel mesh and flows along the conical seat into the detection area of ​​the saccharimeter, facilitating sugar content detection through the saccharimeter itself, thus replacing manual squeezing of the fruit tissue. However, this device has the following technical problems: ① It requires destructive treatment of the fruit, damaging its integrity; ② It does not innovate the detection principle, only adding a mechanical squeezing device; ③ Although it limits the size of the device, it is still not portable enough.

[0005] Some fruit sugar content detection devices are non-destructive testing methods, such as Chinese utility model patent CN209264564U, which discloses a portable fruit sugar content detection device. This utility model includes a shell, a tray, a light shield, and a detection module. The detection module includes a laser diode, a photodetector, a display screen, a processor, and a power supply. The photodetector is connected to the processor sequentially through a photoelectric conversion circuit, a filtering circuit, and an A / D conversion circuit. The laser diode and the display screen are respectively connected to the processor, and the power supply is connected to the processor for power. The laser diode and photodetector are fixed to multiple through-holes on the tray. The laser diode illuminates the fruit placed on the tray, and the diffuse reflected light signal generated inside the fruit is received by the photodetector, processed by the photoelectric conversion circuit, the filtering circuit, and the A / D conversion circuit, and then transmitted to the processor. The problems with this device are: ① It has certain limitations on application scenarios; ② The detection instrument is relatively large and inconvenient to carry; ③ The operation and detection process are not convenient enough. Utility Model Content

[0006] The technical problem to be solved by this utility model is to provide an apple sugar content detection system based on electrical impedance, which can detect sugar content while ensuring the integrity of the apple. It is small in size, portable, has a wide range of applications, and is simple and convenient to operate, thus better meeting the needs of apple sugar content detection.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] An apple sugar content detection system based on electrical impedance includes a main control and display module, an excitation signal generation module, a signal conditioning module, an amplitude and phase detection module, an A / D conversion module, and a power supply module;

[0009] The main control and display modules are electrically connected to the measuring electrodes in sequence through an A / D conversion module, an amplitude and phase detection module, a signal conditioning module, and a signal holding circuit.

[0010] The main control and display modules are also electrically connected to the excitation electrodes in sequence through an excitation signal generation module, a bandpass filter, and a voltage-controlled constant current source circuit;

[0011] The measuring electrode and the excitation electrode are attached to the surface of the apple;

[0012] The power supply module provides power to this system.

[0013] The functions of each module or component are explained below:

[0014] The main control and display module includes an STM32 chip and an OLED display module, which contains a sugar prediction model and is responsible for system function control, data processing, and result display.

[0015] The excitation signal generation module is used to output an excitation signal (100Hz~60KHz) by sweeping the frequency of the apple tissue according to the required step value.

[0016] The signal conditioning module mainly includes a bandpass filter and an operational amplifier circuit, which are used to improve system stability, increase the signal-to-noise ratio, filter out high-frequency harmonic interference contained in the excitation generated by the excitation signal generation module and further enhance the driving capability of the excitation signal, while also performing certain processing on the measurement signal.

[0017] The amplitude and phase detection module is used to measure the amplitude ratio and phase difference of the output signal of the signal conditioning module, and output the measurement results in the form of an analog voltage signal.

[0018] The A / D conversion module is used to convert the detection result (analog signal) output by the amplitude and phase detection module into digital information that the control module can recognize.

[0019] The working principle and process of this utility model are as follows:

[0020] The excitation signal is generated by the excitation signal generation module controlled by the main control and display module. The excitation signal is conditioned by a bandpass filter and a voltage-controlled constant current source circuit (to filter out high-frequency harmonic interference, etc.), and then enters the apple tissue through the silver excitation electrode. The measurement signal containing apple characteristic parameters is collected by the silver measurement electrode and enters the amplitude and phase detection module through the signal conditioning module, thereby measuring the amplitude and phase information. The analog signal is converted into a digital signal by the A / D conversion module, preprocessed, and then transmitted to the main control and display module, which contains the apple sugar content prediction model, to predict its sugar content and display the prediction results.

[0021] It should be noted that the circuit boards and other instruments of this utility model are placed in a small stainless steel shielded box, and the signal transmission lines used for measurement are all shielded wires. The output of the conditioning circuit adopts a low-impedance design to improve the common-mode rejection ratio of the circuit.

[0022] As a further improvement to this technical solution:

[0023] The main control and display module includes an STM32 chip and an OLED display module.

[0024] The excitation signal generation module is the AD9954 chip manufactured by Analog Devices (ADI). This chip integrates a 14-bit high-performance digital-to-analog converter with 14-bit phase adjustment accuracy and 32-bit frequency tuning accuracy. It can simulate and output a stable sine wave signal of up to 160MHz, and it is small in size and has low power consumption of only 200mW.

[0025] The aforementioned measuring electrode and excitation electrode are each provided in two forms.

[0026] The power supply module includes an external DC +12V power supply and a 12V lithium battery.

[0027] The excitation signal generation module uses Direct Digital Synthesis (DDS) technology as the excitation signal generation device, and is equipped with a bandpass filter and a voltage-controlled constant current source circuit to reduce the interference of high-frequency harmonics and noise, and converts the voltage signal into a current signal to provide a more stable excitation signal.

[0028] The amplitude and phase detection module is equipped with an amplitude and phase detector, a DC blocking capacitor, and an RC filter. The signal to be measured enters the amplitude and phase detector after passing through the DC blocking capacitor and the RC filter.

[0029] Both the measuring electrode and the excitation electrode are silver patches covered with soft rubber. The silver electrodes are attached to the elastic rubber to better conform to the apple surface during the detection process.

[0030] The following beneficial effects are achieved by adopting the technical solution described in this utility model:

[0031] (1) In view of the problem that traditional testing requires destructive treatment of fruit, this utility model proposes a non-destructive testing method for detecting apple sugar content based on bioelectrical impedance analysis.

[0032] (2) In view of the problem that existing non-destructive testing devices (most of which are spectral detection) are large in size and inconvenient to carry, this utility model designs a highly integrated hardware system based on the principle of bioelectrical impedance, which is small in size and easy to operate.

[0033] (3) In view of the problem that existing non-destructive testing devices have certain limitations on application scenarios and require apples to be tested under certain light source conditions after picking, this utility model adopts the principle of bioelectrical impedance detection. It can not only perform non-destructive testing on apples after picking without additional light source conditions, but also be used with automated picking devices to detect unpicked apples on the tree, thereby determining whether to pick them and improving the quality of picking.

[0034] (4) In view of the problem that the operation and testing process of the existing testing device are not convenient enough, and the apples need to be manually sampled or placed inside a specific testing device before testing can be carried out, this utility model uses excitation electrodes and detection electrodes to test the apples. The excitation electrodes and detection electrodes only need to be attached to the surface of the apples to obtain the test results, which is simple to operate. Attached Figure Description

[0035] Figure 1 This is a block diagram showing the main control and display modules.

[0036] Figure 2 This is a schematic diagram of an electrostatic discharge (ESD) protection circuit.

[0037] Figure 3 This is a schematic diagram of a voltage-controlled constant current source circuit.

[0038] Figure 4 Schematic diagram of a signal holding circuit

[0039] Figure 5 Diagram showing the positions of the excitation and detection electrodes.

[0040] Figure 6 This is a framework diagram of the system.

[0041] Explanation of reference numerals in the attached diagram: 1-Main control and display module, 2-Excitation signal generation module, 3-Signal conditioning module, 4-Amplitude and phase detection module, 5-A / D conversion module, 6-Signal holding circuit, 7-Bandpass filter, 8-Voltage controlled constant current source circuit, 9-Excitation electrode, 10-Measurement electrode. Detailed Implementation

[0042] The present invention will be further described below with reference to the embodiments.

[0043] See Figures 1-6As can be seen, the apple sugar content detection system based on electrical impedance to this invention comprises a main control and display module 1, an excitation signal generation module 2, a signal conditioning module 3, an amplitude and phase detection module 4, an A / D conversion module 5, and a power supply module. The main control and display module 1 is electrically connected to the measuring electrode 10 in sequence through the A / D conversion module 5, the amplitude and phase detection module 4, the signal conditioning module 3, and the signal holding circuit 6. The main control and display module 1 is also electrically connected to the excitation electrode 9 in sequence through the excitation signal generation module 2, the bandpass filter 7, and the voltage-controlled constant current source circuit 8. The measuring electrode 10 and the excitation electrode 9 are attached to the surface of the apple. The power supply module provides power to this system.

[0044] The functions of each module or component are explained below:

[0045] The main control and display module 1 includes an STM32 chip and an OLED display module. It contains a sugar prediction model and is responsible for system function control, data processing, and result display.

[0046] The excitation signal generation module 2 is used to sweep the frequency of the apple tissue according to the required step value and output an excitation signal 100H. z ~60KH z .

[0047] The signal conditioning module 3 mainly includes a bandpass filter 7, an operational amplifier circuit, etc., which are used to improve system stability, increase the signal-to-noise ratio, filter out high-frequency harmonic interference contained in the excitation generated by the excitation signal generation module 2 and further enhance the driving capability of the excitation signal, while also performing certain processing on the measurement signal.

[0048] The amplitude and phase detection module 4 is used to measure the amplitude ratio and phase difference of the output signal of the signal conditioning module 3, and output the measurement results in the form of an analog voltage signal.

[0049] The A / D conversion module 5 is used to convert the analog signal of the detection result output by the amplitude and phase detection module into digital information that can be recognized by the control module.

[0050] The main control and display module 1 includes an STM32 chip and an OLED display module.

[0051] The excitation signal generation module 2 is an AD9954 chip manufactured by Analog Devices (ADI). This chip integrates a 14-bit high-performance digital-to-analog converter (DAC) with 14-bit phase adjustment accuracy and 32-bit frequency tuning accuracy. It can simulate a stable sine wave signal up to 160MHz and is small in size with low power consumption of only 200mW. The output current of this DDS is determined by the grounding resistor R on pin 24. set To control it, the relationship is:

[0052] Rset =(39.19 / I out )Ω

[0053] Simultaneously, the resistance R set The resistance value is selected as 3.9KΩ, and the DDS output is limited to within 10mA.

[0054] The measuring electrode 10 and the excitation electrode 9 are each provided in two.

[0055] The power supply module includes an external +12V DC power supply and a 12V lithium battery. To ensure a stable power supply and from a practical use perspective, the power supply module uses both an external +12V DC power supply and a 12V lithium battery, and then the voltage is stepped down to the required value by a DC-DC step-down converter.

[0056] The excitation signal generation module 2 uses Direct Digital Synthesis (DDS) technology as the excitation signal generation device, and is equipped with a bandpass filter 7 and a voltage-controlled constant current source circuit 8 to reduce the interference of high-frequency harmonics and noise, and converts the voltage signal into a current signal to provide a more stable excitation signal.

[0057] The amplitude and phase detection module 4 is equipped with an amplitude and phase detector, a DC blocking capacitor, and an RC filter. The signal to be measured enters the amplitude and phase detector after passing through the DC blocking capacitor and the RC filter.

[0058] The measuring electrode 10 and the excitation electrode 9 are both silver patches covered with soft rubber. The silver electrodes are attached to the elastic rubber to better adhere to the apple surface during the detection process.

[0059] A signal holding circuit 6 is built after each measuring electrode 10, as shown in the schematic diagram. Figure 4 As shown, a first-order active high-pass filter is built around the AD8672ARZ operational amplifier. This filter can remove low-frequency interference signals and power frequency signals from the signal acquisition source and has a sufficiently high input impedance to prevent the excitation signal current from flowing into the measurement electrode 10. V1 is a clamping diode that clamps the input signal within -5V to +5V, providing some static protection and preventing damage to the internal circuitry due to high input voltage caused by incorrect operation. C54 is a DC blocking capacitor that filters out the DC component in the measurement signal and forms a high-pass filter structure with R30.

[0060] The working principle and process of this utility model are as follows:

[0061] like Figure 5 As shown, when using this design to test apples, such as Figure 5As shown, the excitation electrode 9 and the detection electrode are first attached to the apple surface. The excitation signal is generated by the excitation signal generation module 2 controlled by the main control and display module 1. The excitation signal is conditioned and filtered by the bandpass filter 7 and the voltage-controlled constant current source circuit 8 to remove high-frequency harmonic interference, etc. Then, it enters the apple tissue through the silver excitation electrode 9. The measurement signal containing the apple's characteristic parameters is collected by the silver measurement electrode 10. It enters the amplitude and phase detection module 4 through the signal conditioning module 3, and then the amplitude and phase information are measured. The analog signal is converted into a digital signal by the A / D conversion module 5. After preprocessing, it is transmitted to the main control and display module 1, which has an apple sugar content prediction model, to predict its sugar content and display the prediction results.

[0062] It should be noted that the circuit boards and other instruments of this utility model are placed in a small stainless steel shielded box, and the signal transmission lines used for measurement are all shielded wires. The output of the conditioning circuit adopts a low-impedance design to improve the common-mode rejection ratio of the circuit.

[0063] The following beneficial effects are achieved by adopting the technical solution described in this utility model:

[0064] (1) In view of the problem that traditional testing requires destructive treatment of fruit, this utility model proposes a non-destructive testing method for detecting apple sugar content based on bioelectrical impedance analysis.

[0065] (2) In view of the problem that existing non-destructive testing devices (most of which are spectral detection) are large in size and inconvenient to carry, this utility model designs a highly integrated hardware system based on the principle of bioelectrical impedance, which is small in size and easy to operate.

[0066] (3) In view of the problem that existing non-destructive testing devices have certain limitations on application scenarios and require apples to be tested under certain light source conditions after picking, this utility model adopts the principle of bioelectrical impedance detection. It can not only perform non-destructive testing on apples after picking without additional light source conditions, but also be used with automated picking devices to detect unpicked apples on the tree, thereby determining whether to pick them and improving the quality of picking.

[0067] (4) In view of the problem that the operation and testing process of the existing testing device are not convenient enough, and the apples need to be manually sampled or placed inside a specific testing device before testing can be carried out, this utility model uses excitation electrodes and detection electrodes to test the apples. The excitation electrodes and detection electrodes only need to be attached to the surface of the apples to obtain the test results, which is simple to operate.

[0068] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. All components not explicitly stated in this embodiment can be implemented using existing technology.

Claims

1. An apple sugar content detection system based on electrical impedance, comprising a main control and display module (1), an excitation signal generation module (2), a signal conditioning module (3), an amplitude and phase detection module (4), an A / D conversion module (5), and a power supply module, characterized in that: The main control and display module (1) is electrically connected to the measuring electrode (10) in sequence through the A / D conversion module (5), the amplitude and phase detection module (4), the signal conditioning module (3), and the signal holding circuit (6); The main control and display module (1) is also electrically connected to the excitation electrode (9) in sequence through the excitation signal generation module (2), the bandpass filter (7), and the voltage-controlled constant current source circuit (8); The measuring electrode (10) and the excitation electrode (9) are attached to the surface of the apple; The power supply module provides power to this system.

2. The apple sugar content detection system based on electrical impedance as described in claim 1, characterized in that: The main control and display module (1) includes an STM32 chip and an OLED display module.

3. The apple sugar content detection system based on electrical impedance as described in claim 1, characterized in that: The excitation signal generation module (2) is an AD9954 chip manufactured by Analog Devices.

4. The apple sugar content detection system based on electrical impedance as described in claim 1, characterized in that: The measuring electrode (10) and the excitation electrode (9) are each provided in two.

5. The apple sugar content detection system based on electrical impedance as described in claim 1, characterized in that: The power supply module includes an external DC +12V power supply and a 12V lithium battery.

6. The apple sugar content detection system based on electrical impedance as described in claim 1, characterized in that: The excitation signal generation module (2) uses Direct Digital Synthesis (DDS) technology as the excitation signal generation device, and is equipped with a bandpass filter (7) and a voltage-controlled constant current source circuit (8) to reduce the interference of high-frequency harmonics and noise, and convert the voltage signal into a current signal.

7. The apple sugar content detection system based on electrical impedance as described in claim 1, characterized in that: The amplitude and phase detection module (4) is equipped with an amplitude and phase detector, a DC blocking capacitor, and an RC filter. The signal to be measured enters the amplitude and phase detector after passing through the DC blocking capacitor and the RC filter.

8. The apple sugar content detection system based on electrical impedance as described in claim 1, characterized in that: The measuring electrode (10) and the excitation electrode (9) are both made of silver patches covered with soft rubber.

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