Tomato water content detection device based on flexible electrode

Abstract

The utility model relates to the field of tomato water content detection, in particular to a tomato water content detection device based on a flexible electrode, which can realize dynamic water content monitoring in the whole life cycle of tomato fruits. Comprising a main control chip, a capacitance detection module, a temperature and humidity sensor, a flexible electrode and a reference capacitor, the positive electrode of the flexible electrode is connected to a first channel of the capacitance detection module, the flexible electrode and the tomato surface form a capacitor, and the positive electrode of the reference capacitor is connected to a second channel of the capacitance detection module to form a differential capacitor. An SDA pin of the capacitance detection module is connected with a fourth pin of the main control chip, an SCL pin of the capacitance detection module is connected with a fifth corner of the main control chip, an SDA pin of the temperature and humidity sensor is connected with the fourth pin of the main control chip, an SCL pin of the temperature and humidity sensor is connected with the fifth corner of the main control chip, and the capacitance detection module transmits a detected capacitance value to the main control chip. The device is suitable for tomato water content detection.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of tomato water content detection, concretely relates to a kind of tomato water content detection device based on flexible electrode. BACKGROUND

[0002] In the field of agriculture, as a widely planted and important economic value crop, the quality and storage characteristics of tomato have been the focus of research. Moisture content is a key factor affecting tomato quality, processing performance and storage period. Accurate determination of the moisture content of tomato is of great significance for the planting management, determination of harvesting time, optimization of processing technology and development of storage preservation strategy. Due to the limitations of technology and equipment, the traditional drying method has been the commonly used means for determining the moisture content of tomato. With the progress of science and technology, the traditional drying method gradually reveals its drawbacks due to its long measurement time, large sample destruction, large measurement error and high dependence on equipment.

[0003] Studies have shown that water accounts for the largest proportion in most plant bodies. The water content inside the fruit continuously changes with the physiological activities of the plant, especially under the stimulation of the external environment. Water in plants is mainly divided into two categories: free water and bound water. Free water accounts for a larger proportion and is easily affected by external factors, while bound water accounts for a smaller proportion and is not easily lost. Water molecules are polar molecules due to the non-coincidence of their positive and negative charge centers. In the absence of an external electric field, water molecules are in a disordered arrangement, but when subjected to an external electric field, water molecules will move due to the electric field force. Therefore, tomato fruits can be regarded as a dielectric, similar to general dielectrics, and their characteristics can be described by an equivalent circuit model.

[0004] Existing detection techniques, such as plant leaf water detection based on capacitors, treat leaves as capacitors to explore the relationship between leaf capacitance and water content, proving that organic substances containing water molecules can be regarded as a dielectric to establish a relationship between dielectric spectrum and water content. However, this research is only applicable to in vitro leaves.

[0005] Therefore, the utility model provides a device for detecting the in vivo moisture content of tomato based on flexible electrode capacitors, which realizes the correction of the complex linear relationship between the dielectric constant of tomato fruit and water content, and more accurately detects the water content of tomato fruit. UTILITY MODEL CONTENT

[0006] The utility model aims to overcome the shortcomings of the prior art and provide a tomato water content detection device based on flexible electrode, which realizes dynamic monitoring of the water content of tomato fruit throughout its life cycle and improves detection efficiency.

[0007] The utility model discloses the following technical scheme to realize the above-mentioned purpose, and the utility model provides a kind of tomato water content detection device based on flexible electrode, including main control chip 001, capacitance detection module 002, temperature and humidity sensor 003, flexible electrode 004, reference capacitor 010, the positive pole of flexible electrode 004 is accessed the first channel of capacitance detection module 002, flexible electrode 004 and tomato surface form capacitor, the positive pole of reference capacitor 010 is accessed the second channel of capacitance detection module 002, forms differential capacitor, the SDA foot of capacitance detection module 002 is connected with the fourth foot of main control chip 001, the SCL foot of capacitance detection module 002 is connected with the fifth angle of main control chip 001, the SDA foot of temperature and humidity sensor 003 is connected with the fourth foot of main control chip 001, the SCL foot of temperature and humidity sensor 003 is connected with the fifth angle of main control chip 001, capacitance detection module 002 transmits the capacitor value of detection to main control chip 001.

[0008] Further, the second channel of capacitance detection module 002 accesses 10pF ceramic capacitor of fixed precision ±1%, eliminates environmental common-mode noise by differential measurement.

[0009] Further, the device further includes display module 005, the SDA foot of display module 005 is connected with the fourth foot of main control chip 001, and the SCL foot of display module 005 is connected with the fifth angle of main control chip 001.

[0010] Further, the device further includes power module 006, power module 006 installs 18650 lithium battery, and 5V power supply is output by 3.7V boost module.

[0011] Further, the device further includes circuit board 008, and the main control chip 001, capacitance detection module 002, temperature and humidity sensor 003, flexible electrode 004, reference capacitor 010, display module 005 and power module 006 are installed on circuit board 008.

[0012] Further, circuit board 008 is placed in transparent acrylic plate box 009, and is screwed around by thread screw 017, and wire is transmitted from front end circular hole 016.

[0013] Further, the flexible electrode 004 is composed of normal temperature plasticity plastic layer 013, silica gel layer 014 and flexible material layer 015, the normal temperature plasticity plastic layer 013 is made into the spherical body of 30mm diameter, and is provided with a first opening of 15mm diameter and a second opening of 5mm diameter, the first opening is used as the entrance of tomato, and the second opening is used as the wire outlet of flexible electrode 004, the normal temperature plasticity plastic layer 013 is evenly spread with 1mm silica gel layer 014, and flexible material layer 015 is closely attached to the inner wall.

[0014] The utility model discloses the beneficial effect is:

[0015] The utility model discloses the nondestructive testing, flexible capacitor carbon electrode is attached the surface of tomato, does not need to pick, improves the detection efficiency, utilizes the device, and the researcher can carry out the continuous moisture content detection of the tomato fruit on the same plant in different growth stages, thereby obtains more accurate and consistent experimental data. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is the structure schematic diagram of tomato water content detection device based on flexible electrode that the utility model embodiment provides;

[0017] Figure 2 It is the structure schematic diagram on circuit board that the utility model embodiment provides;

[0018] Figure 3 It is the layered structure schematic diagram of flexible electrode assembly material that the utility model embodiment provides;

[0019] Figure 4 It is the appearance structure schematic diagram of device that the utility model embodiment provides. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantage of the utility model embodiment more clearly, the technical scheme in the utility model embodiment will be clearly and completely described below in conjunction with the drawings in the utility model embodiment.

[0021] The utility model provides a kind of tomato water content detection device based on flexible electrode, as Figure 1 As shown, detection device includes main control chip 001, capacitance detection module 002, temperature and humidity sensor 003, flexible electrode 004, display module 005, power module 006, wire 007, circuit board 008, acrylic cover plate 009, reference capacitor 010, in main control chip 001, there is the relationship model of water content and capacitance value embeddedly arranged.

[0022] Main control chip 001, capacitance detection module 002, temperature and humidity sensor 003, flexible electrode 004, power module 006, reference capacitor 010 and display module 005 etc. Hardware is arranged on circuit board 008, and assembly component is as Figure 2 As shown, its connection relationship is as follows:

[0023] The positive pole of flexible electrode is connected to the first channel of capacitance detection module, and electrode and tomato surface form capacitor.

[0024] The positive pole of the reference capacitor is connected to the second channel to form a differential capacitor. The second channel is connected to a 10pF ceramic capacitor with a fixed precision of ±1%, and the environmental common-mode noise is eliminated through differential measurement.

[0025] The SDA (data line) pin of the capacitor detection module 002 is connected to the A4 pin of the master chip, the SCL (control line) pin is connected to the A5 pin, and the VCC pin is connected to the 3.3V power supply. The capacitor sensor transmits the capacitance value to the master chip through the I 2 C protocol.

[0026] The SDA pin and SCL pin of the temperature and humidity sensor 003 are also connected to the A4 pin and A5 pin (share I 2 C bus) of the master chip.

[0027] The SDA pin and SCL pin of the display module 005 are also connected to the A4 pin and A5 pin of the master chip, and the pre-compiled firmware on the master chip is used to confirm that the OLED display initialization is completed.

[0028] Connect the power module 006, install the 18650 lithium battery, and output 5V power supply through the 3.7V boost module.

[0029] Specifically, the assembled circuit board is placed in a transparent acrylic box 009, and the threaded screws 017 are tightened around the perimeter, and the wires are transmitted from the front circular hole (016).

[0030] Specifically, the flexible electrode 004 of the capacitor is prepared, which is composed of a room temperature plastic layer 013, a silica gel layer 014, and a flexible material layer 015. The flexible electrode assembly structure of the flexible electrode capacitor is as Figure 3 shown, and the specific preparation process is as follows:

[0031] The room temperature plastic layer 013 is made into a spherical body with a diameter of 30mm, and has an opening (tomato inlet) with a diameter of 15mm and an opening (used as a flexible electrode wire outlet) with a diameter of 5mm. The room temperature plastic layer 013 is uniformly covered with 1mm of silica gel 014 to ensure flexibility and insulation. The flexible electrode material 015 is tightly attached to the inner wall, and the electrode wire is connected to the capacitor detection module through the reserved outlet, and the final assembled detection device appearance front view is as Figure 4 shown.

[0032] The moisture content of the tomato is measured by the assembled detection device, and the specific operation steps of the device are as follows:

[0033] Preheat the equipment, put the battery into the power module, press the lower circular button 018, and start the machine. After starting, stand for 1 minute, wait for the sensor to stabilize, and reach thermal equilibrium.

[0034] Put the tomato into the flexible electrode, press the outer plastic shell, ensure that the tomato is closely attached to the flexible electrode, and ensure that the length of the flexible electrode in contact with the surface is ≥80%. If there is water on the surface of the tomato, it needs to be wiped dry and measured after waiting for 10 seconds to avoid interference from the surface water film.

[0035] Start detection, OLED displays "Measuring...", and displays the result (such as "Water: 92.3%") after 2 seconds. If it displays "Error", reattach the electrode and measure again.

[0036] Synchronize data, upgrade the Bluetooth transmission protocol to low-power BLE 5.0, and support batch data export.

[0037] After measurement, the electrode needs to be cleaned, the electrode surface is wiped with a 75% alcohol cotton swab, and is stored after drying. Every month, a standard water content tomato is verified, if the error is >3%, it needs to be reset, re-collect data, train the model, connect the master chip to the PC end, press the square button below (019), and re-import the corrected function relationship between water content and capacitance value into the master chip. Check the FDC1004 reference voltage every half year (it needs to be stable at 1.8V±0.1V), and replace the module when the deviation is too large.

[0038] The water content detection step of the utility model through the detection device specifically includes:

[0039] S1. Collection of tomatoes used in the experiment;

[0040] S2. Measure the capacitance value and loss factor of different tomato water content using experimental instruments, and use the actual tomato water content measured by the drying method as the standard;

[0041] S3. Derive the functional relationship between the actual tomato water content and the measured capacitance value;

[0042] S4. Import the capacitance value and water content prediction model into the detection device chip, and assemble the tomato in vivo water content detection equipment;

[0043] S5. The detection equipment is used for actual tomato measurement, and the tomato water content can be directly obtained through the equipment.

[0044] Specifically, the tomatoes of step S1 are fresh picked mature fruits with different water deficit experiments.

[0045] Specifically, the operation of step S2 is:

[0046] The experimental apparatus used was an LCR meter. Utilizing the instrument's test voltage range of 0.1-2.0V in 0.01V increments, the capacitance (CP) and loss factor (D) of tomato fruits with different moisture contents were measured. Based on the capacitor principle, the dielectric parameters were calculated. The calculation formula is shown below:

[0047]

[0048] In the formula, C is the capacitance, i.e., the CP obtained by the experiment, ε0 is the vacuum dielectric constant, ε0=8.85*1012F / m, d is the electrode plate spacing, s is the area of ​​the parallel plates, tanδ is the dielectric loss tangent, and δ is the dielectric loss angle.

[0049] The values ​​ε′ and ε″ of the blade sample can be obtained using the formulas for calculating capacitance and dielectric loss tangent.

[0050]

[0051] ε″=ε′tanδ=ε′D

[0052] In the formula, D is the loss factor measured by the LCR measuring instrument, i.e., tanδ.

[0053] After measuring the dielectric spectral properties of each tomato, the tomato samples were placed on an electronic balance to determine their fresh weight. Once the fresh weight data for all tomato samples were obtained, the samples were uniformly placed in a drying oven at 105℃ for drying. Based on the difference between the fresh weight and dry weight data before and after drying, the actual moisture content of each tomato sample was calculated. The specific calculation formula is as follows:

[0054]

[0055] In the formula, MC is the moisture content of the tomato fruit, FW is the fresh weight of the tomato fruit, and DW is the dry weight of the tomato fruit.

[0056] The functional relationship between the tomato water content and dielectric constant in step S3 is determined as follows:

[0057] First, the actual tomato water content and dielectric constant are corrected. Then, the IRIV feature selection algorithm is used to screen key frequency points. The specific method is described by the following equation:

[0058] 1. Initialize the full frequency set S = {f1, f2, ..., f37} (37 pre-selected frequencies)

[0059] 2. Calculate the removal contribution for each frequency:

[0060] ΔRMSEi=RMSE(S)-RMSE(S / {fi})

[0061] 3. Eliminate ΔRMSE iThe minimum frequency is iterated to retain 3 optimal frequencies.

[0062] Further, when 3 optimal frequencies are selected, IFOA-SVR algorithm is used for modeling, improved fruit fly optimization algorithm (IFOA) is used to optimize SVR parameters, and the optimized SVR model is used to establish a tomato water content prediction formula, which is the key to ensure the accuracy of the actual tomato water content measurement value. First, the parameters C in the SVR model are constrained, C is the penalty coefficient, which controls the punishment intensity of the model to the samples exceeding the error band in the training data, g is the kernel function, which adjusts the distribution density of data in the feature space and affects the capture ability of the model to nonlinear relationship, ∈ boundary range is the insensitive loss coefficient, which defines the error tolerance band between the predicted value and the true value, and C ∈ [2 -14 ,2 14 ], g ∈ [2 -14 ,2 14 ], ∈ ∈ [2 -14 ,2 14 ] are taken, the constraint range is to speed up the convergence and prevent numerical overflow. Further, the fitness function Fitness in the improved fruit fly optimization algorithm (IFOA) is determined, Fitness = 0.5 × MAE + 0.3 × RMSE + 0.2 × MAPE, wherein MAE (mean absolute error): reflects the absolute level of prediction error, weight 50% to ensure basic accuracy, RMSE (root mean square error): sensitive to outliers, weight 30% to suppress large deviations, MAPE (mean absolute percentage error): relative error measure, weight 20%, adapt to different water content range. The purpose of fitness evaluation is to train the SVR model with each data individual, calculate the Fitness value, and record the current optimal parameter combination (C, g, ∈). Further, the quantum potential well position update X new : position of the new generation of fruit fly individuals (i.e. parameter combination C, g, ∈ to be optimized), X best : position of the current global optimal individual (historical optimal parameter combination), L current : adaptive step size, : inertia weight, randn(): standard normal distribution random number. The purpose is to avoid falling into local optimal parameter combination and ensure finding the global optimal parameter combination. Further, when the global optimal parameter combination is found, the SVR prediction formula can be established:

[0063]

[0064] wherein MC is the water content of tomato fruit, K(x i ,x) = exp(-γ‖x i -x‖ 2) is the RBF kernel function. x = [Cf1, Cf2, Cf3, T, H] is the input feature vector, T represents temperature (℃), and H represents humidity (%RH).

[0065] The utility model discloses a specific detection device utilizes the dielectric constant of tomato, establishes tomato dielectric spectrum + SVR prediction model, and then utilizes IRIV-IFOA algorithm to optimize dielectric spectrum + SVR prediction model, finds out the optimal parameter in dielectric spectrum + SVR model, establishes accurate SVR prediction formula, obtains the function relation of high-precision tomato water content and capacitance value, and deeply considers environmental temperature humidity and other influence parameters, utilizes differential capacitance and other means to reduce error, aims at avoiding that traditional method has significant influence on measurement result in the research of determining the water content in the growth cycle of tomato, and then causes the experimental data to appear larger deviation, and provides a kind of novel non-destructive fruit in-body water content detection device. The device realizes non-invasive detection, i.e. measurement is carried out under the premise of not damaging tomato fruit. Using the device, researchers can continuously detect the water content of tomato fruits on the same plant in different growth stages, so as to obtain more accurate and consistent experimental data.

[0066] The above is only the preferred embodiment of the utility model, and it should be understood that the utility model is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein by the above teaching or related technical or knowledge. The modification and change made by the person in the art without departing from the spirit and scope of the utility model should be within the protection scope of the claims attached to the utility model.

Claims

1. A flexible electrode based device for detecting water content in tomatoes, characterized in that, The device comprises a main control chip (001), a capacitance detection module (002), a temperature and humidity sensor (003), a flexible electrode (004), and a reference capacitor (010). The positive electrode of the flexible electrode (004) is connected to the first channel of the capacitance detection module (002), and the flexible electrode (004) forms a capacitance with the surface of the tomato. The positive electrode of the reference capacitor (010) is connected to the second channel of the capacitance detection module (002), forming a differential capacitance. The SDA pin of the capacitance detection module (002) is connected to the fourth pin of the main control chip (001), and the SCL pin of the capacitance detection module (002) is connected to the fifth pin of the main control chip (001). The SDA pin of the temperature and humidity sensor (003) is connected to the fourth pin of the main control chip (001), and the SCL pin of the temperature and humidity sensor (003) is connected to the fifth pin of the main control chip (001). The capacitance detection module (002) transmits the detected capacitance value to the main control chip (001).

2. The flexible electrode-based tomato water content detection device of claim 1, wherein, The second channel is connected to a fixed precision ±1% 10pF ceramic capacitor, and the environmental common mode noise is eliminated by differential measurement.

3. The flexible electrode-based tomato water content detection device of claim 2, wherein, The device also comprises a display module (005), and the SDA pin of the display module (005) is connected to the fourth pin of the main control chip (001), and the SCL pin of the display module (005) is connected to the fifth pin of the main control chip (001).

4. The flexible electrode-based tomato water content detection device of claim 3, wherein, The device also comprises a power module (006), and the power module (006) is installed with a 18650 lithium battery, and outputs 5V power supply through a 3.7V boost module.

5. The flexible electrode-based tomato water content detection device of claim 4, wherein, The device also comprises a circuit board (008), and the main control chip (001), the capacitance detection module (002), the temperature and humidity sensor (003), the flexible electrode (004), the reference capacitor (010), the display module (005), and the power module (006) are installed on the circuit board (008).

6. The flexible electrode-based tomato water content detection device of claim 5, wherein, The circuit board (008) is placed in a transparent acrylic box (009), and the wires are transmitted from the front circular hole (016).

7. The flexible electrode-based tomato water content detection device of claim 1, wherein, The flexible electrode (004) is composed of a room temperature plastic layer (013), a silica gel layer (014), and a flexible material layer (015). The room temperature plastic layer (013) is made into a sphere with a diameter of 30mm, and a first opening with a diameter of 15mm and a second opening with a diameter of 5mm are set. The first opening is used as the tomato inlet, and the second opening is used as the wire outlet of the flexible electrode (004). The room temperature plastic layer (013) is evenly covered with a 1mm silica gel layer (014), and the flexible material layer (015) is tightly attached to the inner wall.

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