A device and method for measuring moisture content of wood layers

Abstract

The present application discloses a device and method for measuring the moisture content of wood layers, which relates to the field of moisture content measurement. The device includes an electrode component, a human-machine interaction component and a microcontroller; the electrode component is used to contact any layer of the wood to be measured, and collect voltage information of the corresponding wood layer when the measurement button is triggered; the human-machine interaction component is used to input the size value, angle value and type of the wood to be measured into the microcontroller; the microcontroller is connected to the electrode component and the human-machine interaction component respectively, and the microcontroller is used to: receive voltage information and extract and obtain a sampled voltage value; receive the size value, angle value and type; call the corresponding preset fitting function model according to the angle value and type; based on the preset fitting function model, calculate the moisture content of the wood layers according to the sampled voltage value, size value and angle value. The present application can quickly realize accurate measurement of the moisture content of wood layers.

Description

Technical Field

[0001] The present application relates to the field of moisture content measurement, and in particular to a device and method for measuring the moisture content of wood layers. Background Art

[0002] The moisture distribution of wood plays an important role in wood processing, drying, transportation and storage. At present, there are many methods for determining the moisture content of wood, which are divided into destructive testing and non-destructive testing according to whether it causes damage to the wood. Destructive testing includes weighing method, distillation method and resistance method. Non-destructive testing includes capacitance method, nuclear magnetic resonance method, near infrared spectroscopy, computer tomography scanning method and microwave method.

[0003] Among them, the advantages of the weighing method are: accurate measurement, no limitation on the moisture content measurement range, and wide applicability; the disadvantages are: lossy measurement, inability to measure in layers, and long measurement cycle. The advantages of the distillation method are: simple equipment, wide applicability, and strong repeatability; the disadvantages are: lossy measurement, solvents are harmful to the human body, high cost, inaccurate measurement results, easy to cause reading errors, and inability to measure in layers. The advantages of the resistance method are: real-time and fast measurement, low cost, and high convenience; the disadvantages are: lossy measurement, large errors at low moisture content, and many influencing factors such as density, tree species, and temperature; the measurement range is narrow and inability to perform layered measurement. The advantages of the capacitance method are: non-destructive real-time measurement, high precision, and simple operation; the disadvantages are: the external environment and the placement of the electrodes have a great influence on the results; the advantages of nuclear magnetic resonance technology are: non-destructive measurement, high precision, and layered measurement; the disadvantages are: poor real-time performance, high maintenance cost, external environmental influence, poor equipment convenience, complex operation, and strict maximum measurement size restrictions; the advantages of near-infrared spectroscopy are: non-destructive real-time measurement, accurate measurement, commonly used in continuous single-board detection in factories, and layered measurement; the disadvantages are: tree species correction is required, and the penetration ability is limited. The advantages of computed tomography are: non-destructive, strong penetration, fast detection speed, and high three-dimensional imaging resolution; the disadvantages are: high cost, poor equipment convenience, and radiation exposure problems. The advantages of the microwave method are: non-destructive real-time, layered measurement, high precision, and no need for tree species correction; the disadvantages are: large temperature influence, and the moisture content measurement range and the measurement ability of wood of specific sizes and shapes are limited.

[0004] In summary, the existing wood moisture detection methods have their own advantages and disadvantages, but there are certain limitations in terms of detection accuracy and application convenience. Summary of the invention

[0005] The purpose of the present application is to provide a device and method for measuring the moisture content of wood layers, which can quickly and accurately measure the moisture content of wood layers.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a device for measuring moisture content of wood layers, including an electrode component, a human-computer interaction component, and a microcontroller;

[0008] The electrode component is used to contact any layer of the wood to be tested, and collect voltage information of the corresponding wood layer when the measuring button is triggered;

[0009] The human-machine interaction component is used to input the size value, angle value and type of the wood to be tested into the microcontroller; wherein the angle value takes the chord direction of the wood as 0 degrees;

[0010] The microcontroller is connected to the electrode component and the human-computer interaction component respectively, and the microcontroller is used to: receive the voltage information and extract the sampled voltage value; receive the size value, the angle value and the type; call the corresponding preset fitting function model according to the angle value and the type; calculate the wood stratification moisture content according to the sampled voltage value, the size value and the angle value based on the preset fitting function model; wherein the preset fitting function model realizes angle compensation processing.

[0011] In a second aspect, the present application provides a method for determining the moisture content of wood layers, comprising:

[0012] Install a device for measuring the moisture content of wood layers;

[0013] Input the size, angle and type of the wood to be tested into the microcontroller through the human-computer interaction component;

[0014] Put the electrode component in contact with any layer of the wood to be tested, and trigger the measurement button;

[0015] The microcontroller receives the voltage information corresponding to the wood layer after triggering and extracts the sampled voltage value, and calls the corresponding preset fitting function model according to the angle value and the type; wherein the preset fitting function model realizes the angle compensation processing;

[0016] The microcontroller is used to calculate the wood stratification moisture content according to the sampled voltage value, the size value and the angle value based on the preset fitting function model.

[0017] According to the specific embodiments provided by the present application, the present application has the following technical effects: the present application provides a device and method for measuring the moisture content of wood layers, which uses an electrode component to contact any layer of the wood to be tested, and after pressing the measurement button to trigger, the final moisture content of the wood layers can be obtained through a microcontroller in combination with the input size value, angle value and type, which is faster, simple in structure, and convenient for mobile application. In the microcontroller, according to the angle value and type, the corresponding preset fitting function model is called, and then the moisture content of the wood layers is calculated according to the sampled voltage value, size value and angle value. Since the angle compensation processing is performed, the measured moisture content of the wood layers can be more realistic and more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic diagram of the technical route of a device for measuring moisture content in wood layers provided in one embodiment of the present application.

[0020] Figure 2 A schematic diagram of the component connections of a device for measuring moisture content in wood layers provided in one embodiment of the present application.

[0021] Figure 3 A schematic diagram of the circuit principle of a device for measuring moisture content in wood layers provided in one embodiment of the present application.

[0022] Figure 4 A schematic diagram of a radial correction curve provided in an embodiment of the present application.

[0023] Figure 5 A schematic diagram of the chord-wise stratified sampling results provided in one embodiment of the present application.

[0024] Figure 6 A schematic diagram of radial stratified sampling results provided in an embodiment of the present application.

[0025] Figure 7 A schematic diagram of the results of a 45° cut board in a slicing method comparison provided in an embodiment of the present application.

[0026] Figure 8 A schematic diagram of the results of a radially cut plate in a slicing method comparison provided in an embodiment of the present application.

[0027] Fig. 9 A schematic diagram of the results of a tangentially cut plate in a slicing method comparison provided in an embodiment of the present application.

[0028] Fig.10 A schematic diagram of the results of the single-sided nuclear magnetic resonance comparison of a chord-cut plate provided in one embodiment of the present application.

[0029] Fig.11 A schematic diagram of the results of the radial cut plate provided in one embodiment of the present application in the single-sided nuclear magnetic resonance method comparison.

[0030] Fig.12 A schematic diagram of the results of a 45° cut plate compared using a single-sided nuclear magnetic resonance method according to an embodiment of the present application. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] This application uses wood conductivity and circuit design to develop an instrument within the fiber saturation point, aiming to use the electrical properties of wood to solve the problem of wood moisture stratification, non-destructive real-time accurate measurement, and improve the convenience of equipment. The wood stratification moisture content measuring instrument of this application is practical for optimizing wood drying process, transportation and storage, improving the efficiency of wood use and processing, and understanding the internal moisture distribution of wood.

[0033] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0034] In an exemplary embodiment, the present application provides a device for measuring the moisture content of wood layers, including an electrode component, a human-machine interaction component and a microcontroller. The electrode component is used to contact any layer of the wood to be measured, and collect voltage information of the corresponding wood layer when the measurement button is triggered. The human-machine interaction component is used to input the size value, angle value and type of the wood to be measured into the microcontroller; the angle value is based on the chord direction of the wood as 0 degrees. The microcontroller is connected to the electrode component and the human-machine interaction component respectively, and the microcontroller is used to: receive the voltage information and extract the sampled voltage value; receive the size value, the angle value and the type; call the corresponding preset fitting function model according to the angle value and the type; based on the preset fitting function model, calculate the moisture content of the wood layers according to the sampled voltage value, the size value and the angle value; wherein the preset fitting function model implements angle compensation processing.

[0035] In actual application, the user first places the wood stratification moisture content determination device on a plane, turns on the power switch, and inputs the size value and angle value of the wood to be measured into the microcontroller in sequence through the matrix keyboard (i.e., the human-computer interaction component). After the input is completed, the user holds the electrode of the electrode component, makes the probe electrode parallel to the measured layer of the wood as much as possible, presses the measurement button, and obtains the sampling voltage value of the layer and the wood stratification moisture content after a certain period of time. According to needs, the contact position of the electrode can be changed to perform multiple measurements, and then the average value is calculated to obtain a more accurate wood stratification moisture content. Through the above measurement process, non-destructive real-time stratification detection of wood can be achieved, which has the advantages of strong equipment convenience, low cost, and convenient user operation.

[0036] The design process of the wood layer moisture content determination device in this application involves four major modules: hardware design, software design, wood sample data collection and processing, and model practicality verification. The corresponding technical route can be as follows: Figure 1 As shown, the process of hardware design and software design is combined, while the availability of the final device can be guaranteed.

[0037] In a specific application, in the corresponding hardware setting, the wood layer moisture content determination device also includes a signal amplification circuit, a Schmidt trigger circuit, a timer, a logic gate circuit module, a capacitor module (corresponding to Figure 2 The device includes a single capacitor module in the test chamber), a display screen (specifically, an OLED display screen), a power supply and a voltage regulator. The display screen is connected to the microcontroller, and the display screen is used to display the size value, the angle value, the type, the sampling voltage value and the moisture content of the wood layer, so as to intuitively display the data during the test.

[0038] Specifically, Figure 2As shown, one end of the positive electrode of the electrode component is connected to the input end of the signal amplification circuit, the other end of the positive electrode of the electrode component is in contact with any layer of the wood to be tested, and the negative electrode of the electrode component is grounded. The output end of the signal amplification circuit is connected to the Schmidt trigger circuit, and the output end of the Schmidt trigger circuit is connected to the logic gate circuit module; in a specific application, the positive threshold voltage of the Schmidt trigger circuit is set to be about 2.2V, and the negative threshold voltage is set to be about 2.4V. The timer is a monostable circuit associated with the measurement button. When the measurement button is triggered, the timer is used to continuously output the trigger level to the logic gate circuit module within a preset time length, so that the output voltage of the logic gate circuit module within the preset time length is used to charge the capacitor in the capacitor module; in a specific application, the timer is a 555 timer, and is set as a button-triggered monostable circuit. The output end of the timer and the output end of the Schmidt trigger circuit pass through the logic gate circuit to achieve a timing effect, and the timing time is 2s. In addition, the above logic gate circuit is an AND gate circuit, and the output voltage charges the 10uF capacitor in the capacitor module, and the capacitor is connected in series with a 1K resistor for current limiting.

[0039] The microcontroller is used to extract the voltage extreme value of the capacitor in the capacitor module within the preset time length and use it as the sampled voltage value. In a specific application, the voltage extreme value of the 10uF capacitor in the capacitor module within 2s is obtained by program capture, and the whole process is performed on a soldered PCB board.

[0040] The power supply is connected to the voltage regulator, and the power supply supplies power to the signal amplification circuit, the Schmitt trigger circuit and the timer through the voltage regulator. In a specific application, the power supply provides a 6V voltage to be connected to the voltage regulator, and the voltage regulator continuously outputs a 5V voltage, which is connected to the VCC of all chips.

[0041] In a specific application, such as Figure 3 As shown in the figure, it is a schematic diagram of the circuit principle of the present application. In the corresponding software configuration, PA1 is used as the input terminal of the analog / digital conversion, PA0, PA2-PA7, and PB0 are configured as the matrix keyboard input, PB9 is set as the display screen output serial port, and PA9 is set as the asynchronous serial communication serial port. Figure 3 The BT1 Battery in the figure represents that the voltage regulator and the power supply are integrated into a voltage regulator module, and the structure is: capacitors C1 and C2 are connected in parallel at both ends of the power supply, the first end of capacitor C1 and the first end of capacitor C2 are both connected to LM1117, and the second end of capacitor C1 and the second end of capacitor C2 are both grounded; LM1117 is a low voltage dropout voltage regulator series chip.

[0042] The signal amplifier circuit is Figure 3The amplifier module in is demonstrated, which includes an amplifier, wherein the first end of the amplifier is used for output and is connected to the Schmitt trigger circuit; the second end of the amplifier is used for input, and the second end of the capacitor C2 in the regulator is connected to the second end of the amplifier via the resistor R4; the third end of the amplifier is used for input, and one end of the electrode access point is connected to the third end of the amplifier via the resistor R2; the fourth end of the amplifier is grounded.

[0043] The Schmitt trigger circuit includes a CD4069 chip, wherein the 2Y port in the chip CD4069 is connected to the logic gate circuit via the resistor R5, and the 1A port in the chip CD4069 is connected to the logic gate circuit via the resistor R1; the first end of the amplifier in the signal amplification circuit is connected to the 1A port in the chip CD4069 via the resistor R3.

[0044] Logic gates are connected to Figure 3 The AND logic gate module in the example is shown in Figure 1. The capacitor module is shown in Figure 1. Figure 3 The single capacitor module in the example is shown in Figure 1. Figure 3 The timer monostable circuit module in is used for demonstration.

[0045] The single capacitor module includes a first branch and a second branch connected in parallel, one end of the first branch and the second branch is connected to the output end of the logic gate circuit, and the other end of the first branch and the second branch is connected to the timer monostable circuit module; the first branch includes a resistor R10 and a capacitor C5 connected in series, and the second branch includes a diode D1 and a resistor R11 connected in series.

[0046] The timer monostable circuit module includes a timing chip, a first end of the timing chip is grounded, a second end of the timing chip is connected to VCC via a resistor R7, a third end of the timing chip is connected to a logic gate circuit, a fourth end and an eighth end of the timing chip are both connected to VCC, a fifth end of the timing chip is grounded via a capacitor C4, a sixth end and a seventh end of the timing chip are connected to VCC via a resistor R8; VCC is also connected to a measuring button via a resistor R6 to receive a trigger signal.

[0047] In order to realize the functions corresponding to the above modules or components, it is also necessary to write program code and perform joint debugging of software and hardware to observe whether they are consistent with the simulation results. The specific content of this part is shown in the method example below.

[0048] In another specific application, the device for determining the moisture content of wood layers further comprises a temperature sensor, which is used to detect the layer temperature of the wood to be measured and the ambient temperature, and can display the temperature on a display screen.

[0049] In another specific application, when the type of the wood to be tested is poplar, the microcontroller calls the corresponding preset fitting function model according to the angle value and the type of the wood to be tested, including:

[0050] The first function unit is used for: when the angle value is 90° (radial), the corresponding preset fitting function model is:

[0051] .

[0052] The second function unit is used for: when the angle value is 0° (chord direction), the corresponding preset fitting function model is:

[0053] .

[0054] .

[0055] MC=Z+XZ.

[0056] The third function unit is used for: when the angle value is within the range of 0°-90°, the corresponding preset fitting function model is:

[0057] .

[0058] .

[0059] .

[0060] .

[0061] Where h is the sampling voltage value, MC is the wood stratification moisture content, Z is the value of the first correction equation, XZ is the value of the second correction equation, is the size value, is the angle value, The moisture content value that needs to be compensated for each degree of deviation in each size and texture direction.

[0062] Based on the same inventive concept, the embodiment of the present application also provides a method for determining the moisture content of wood layers. The implementation scheme for solving the problem provided by the method is similar to the implementation scheme recorded in the above-mentioned device, so the specific limitations in one or more method embodiments provided below can refer to the limitations of the device above, and will not be repeated here. The method for determining the moisture content of wood layers of the present application includes:

[0063] Step 100, installing the above-mentioned wood layer moisture content measuring device.

[0064] Step 200, input the size value, angle value and type of the wood to be tested into the microcontroller through the human-computer interaction component.

[0065] Step 300: contact the electrode component with any layer of the wood to be tested, and trigger the measurement button.

[0066] Step 400, using the microcontroller to receive the voltage information corresponding to the wood layering after triggering and extract the sampled voltage value, and calling the corresponding preset fitting function model according to the angle value and the type; wherein the preset fitting function model realizes angle compensation processing.

[0067] Step 500, using the microcontroller to calculate the wood stratification moisture content according to the sampled voltage value, the size value and the angle value based on the preset fitting function model.

[0068] The processing steps completed by the microcontroller in the above steps 400 and 500 can be implemented by the written main logic function code, which contains multiple header files, such as stm32f10x.h, beep.h, delay.h, etc., for calling file built-in functions, defines a macro PRINT for formatted output, and defines multiple floating-point numbers and integer variables. In the main function of the main logic function code, the delay, interrupt priority, serial port, ADC, DHT11 sensor, matrix keyboard, OLED display are first initialized, and then the initial MC, sampled voltage value, angle value and size value are displayed on the OLED display.

[0069] In the process of extracting the sampled voltage value, the corresponding main logic function code: enter a while loop instruction, first read the DHT11 sensor data in the loop, then read the ADC value of the capacitor in the capacitor module and calculate the voltage, read the maximum value of the voltage by comparison, that is, the sampled voltage value, and then update the voltage display. The purpose of reading the DHT11 sensor data in this application is to ensure that the indoor temperature reaches room temperature (25°C), and to conduct experiments on this basis; DHT11 is a temperature and humidity sensor used for temperature measurement to observe whether the current environment meets the experimental conditions.

[0070] In terms of data display on the display screen, the corresponding main logic function code is: after receiving the trigger of pressing the matrix keyboard, the display of the size value and angle value is updated on the OLED screen according to the key value, and the calculated wood stratification moisture content is displayed. Wood with different angle values ​​needs to use different preset fitting function models to calculate the wood stratification moisture content, and the preset fitting function models corresponding to each angle can be found in the above record, which will not be repeated here.

[0071] In another application example, the process of determining the preset fitting function model includes:

[0072] (11) Slicing wood samples of any type and any angle value to obtain wood sample layers with various slice sizes; in a specific application, the angle value can be selected in the tangential direction and radial direction, such as in the tangential direction, slicing is performed according to the slice sizes of 80 mm (T) × 15 mm (R) × 3 mm (L), 60 mm (T) × 15 mm (R) × 3 mm (L), 40 mm (T) × 15 mm (R) × 3 mm (L), and 20 mm (T) × 15 mm (R) × 3 mm (L), where T represents the tangential direction, R represents the radial direction, and L represents the axial direction.

[0073] (12) All the wood samples are separated into layers for moisture absorption and then left to stand; in a specific application, at room temperature (about 25°C), the wood samples are separated into layers and placed in 6 drying dishes containing saturated solutions of MgCl2, KI, NaCl, KCl, K2SO4 and distilled water for moisture absorption for 72 hours to reach an equilibrium moisture content, and the relative saturated humidity is 32.78%, 68.86%, 75.29%, 84.34%, 97.3% and 100% respectively. It should be noted that in this step, slices of one size (such as 10 slices) are placed in each drying dish for data collection. Data collection of one slice of one size is accidental, and data collection of multiple slices can largely avoid the accidental nature of sample voltage collection, proving the correctness and regularity of the adopted theory (conductivity theory). Then, the wood samples are separated into layers and exposed to the air, and data is collected for the wood samples every 2 minutes to obtain a more detailed gradient of different moisture contents.

[0074] During the collection process, it is difficult to measure when the moisture content of the wood layers is lower than about 9% or higher than about 30%. The former is because when the moisture content of the wood is low, the conductivity of the wood is poor, it is difficult to form a conductive circuit, and it is close to being an insulator. It is always in a high-level state in the instrument. After pressing the timing button, the measured value instantly reaches 3.299V (the microcontroller can detect a maximum of 3.3V). The latter is because when it exceeds 30%, the wood has a good conductive path inside, and the wood acts as a conductor in the circuit, that is, it is always in a low-level state in the circuit. After pressing the timing button, the measured value is 0V, the voltage range of the measuring instrument is 0V-3.3V, and the moisture content measurement range is about 9%-28%.

[0075] (13) For each of the wood sample strata, multiple sampling points are determined, and the sampling voltage value and the moisture content of the wood strata at each sampling point are measured; in a specific application, when collecting data in the tangential or radial direction, wood slices whose linear distance between electrodes is parallel or perpendicular to the wood growth rings are selected as much as possible, and samples are collected in sequence for wood slices with lengths of 80 mm, 60 mm, 40 mm, and 20 mm. 50 sample data points are collected for each size for subsequent linear fitting to cover the entire fiber saturation point as much as possible.

[0076] (14) Based on the angle values, size values, sampling voltage values ​​of each sampling point and moisture content of the wood layers corresponding to all the wood sample layers, a nonlinear cubic polynomial is used for surface fitting to obtain a corresponding preset fitting function model.

[0077] In a specific application, a nonlinear cubic polynomial can be used in Matlab to perform surface fitting, followed by an optimal allocation method using stratified sampling for error analysis and correction. Figure 4 The radial correction curve is shown in the figure. The correction equation is then written into the microcontroller to perform stratified sampling according to size. The chordal stratified sampling results are shown in Figure 5 The radial stratified sampling results are shown in Figure 6 As shown in the figure, the results show that 76.25% of the sampling points in the chord direction are within the qualified range (water content ±1%), 23.75% are unqualified, and the error extremes are basically concentrated at about 1.5%. In the radial direction, the qualified rate is 72.5%, and the error extreme is 1.53%, which basically meets the design requirements.

[0078] Since the resistivity in the chord direction is higher than the resistivity in the radial direction, during the measurement process, the voltage collected in the chord direction is higher than the voltage in the radial direction at the same water content and the same size, so the model height in the chord direction is higher than that in the radial direction as a whole, and the chord direction represents 0 degrees and the radial direction represents 90 degrees, so the present application conducts an angle compensation experiment to overcome the error in the texture direction caused by the angle. The specific compensation method is: when the angle value is in the range of (0, 90), based on the preset fitting function model obtained by fitting when the angle value is 0 and the preset fitting function model obtained by fitting when the angle value is 90, angle compensation processing is performed.

[0079] The angle compensation process is as follows: subtract the preset fitting function model obtained when the angle value is 0 from the preset fitting function model obtained when the angle value is 90, and then perform 90-degree averaging to obtain the moisture content value that needs to be compensated for each degree of deviation of each size and texture direction; based on the moisture content value that needs to be compensated for each degree of deviation of each size and texture direction, compensate for the moisture content of wood layers whose angle values ​​are within the range of (0, 90) to obtain the final moisture content of wood layers.

[0080] When the wood species is poplar, the calculation formula for the moisture content value that needs to be compensated for each dimension and each degree of deviation in the grain direction is:

[0081] .

[0082] in, The moisture content value that needs to be compensated for each degree of deviation in each size and texture direction. is the size value, h is the sampling voltage value; (Z+XZ) corresponds to the preset fitting function model obtained by fitting when the angle value is 0.

[0083] When the wood species is poplar, if different types of tree species need to be measured, it is necessary to resample, build the model and calibrate according to the above steps.

[0084] In another specific application, after obtaining the preset fitting function model corresponding to each angle value, verification is performed, one is to verify by comparing the slice method, and the other is to verify by comparing the single-sided nuclear magnetic resonance method.

[0085] Comparison of slicing method: Cut a 40mm (R) × 40mm (T) × 30mm (L) poplar block into multiple 40mm (R) × 40mm (T) × 3mm (L) wood slices according to the tangential, radial and 45° slices. After drying, label and record the weight, and tie them with rubber bands in the order of slicing. Use a dropper to drip 3ml of distilled water on the surface of the slice numbered 1, then wrap it with plastic wrap and let it stand at room temperature for 6 hours to allow the water to gradually diffuse in each slice, so that the whole piece of wood has a moisture content gradient. This method mainly uses the weighing method and the designed instrument for measurement. The comparison results are as follows: Figure 7 , Figure 8 and Fig. 9 As shown, in the measurement results, the three groups of curves all show a good gradient level. During the measurement process, different relative points are selected as much as possible, and the average of multiple measurements represents the moisture content value of the layer. In the comparative experiment, the 1st and 7th layers exceeded the measurement range of the equipment and were not included in the measurement range. Large errors are prone to occur at high and low moisture contents, with the maximum errors being 1.79%, 1.66%, and 1.43%, respectively, and the minimum errors being 0.12%, 0.49%, and 0.44%, respectively. The reasons for the failure may be caused by errors introduced by inaccurate angle cutting; removing the plastic wrap and then measuring the loss of moisture in the wood slices; and the loss of moisture during continuous measurement. Overall, the trend of this application in measuring moisture content is highly consistent with the trend shown by the slicing method, and its measurement error is always controlled within a reasonable range, which fully demonstrates the excellent performance of this application in terms of reliability and practicality.

[0086] Comparison of single-sided nuclear magnetic resonance method: Cut two wooden blocks of 40mm (R) × 40mm (T) × 21mm (L) in radial, tangential and 45° directions with similar weights, record the weight after absolute drying, and place two by two in a drying dish with a relative humidity of 100% to absorb moisture for 72 hours, and quickly seal with plastic wrap; one of the blocks is used for single-sided single-sided nuclear magnetic resonance layered detection, and the average of the results of every three layers of single-sided nuclear magnetic resonance is taken as the average moisture content of each layer of 3mm; one block is used for the measurement of the designed instrument. In order to ensure that each layer (one layer is 3mm) is contacted by the electrode during the measurement process of the instrument and reduce experimental errors, marks are made every 3mm, and the average of five consecutive rapid measurements of the designed instrument is taken as the moisture content value of this layer. The test comparison results are as follows: Fig.10 , Fig.11 and Fig.12 As shown in the figure, in general, in an environment with high relative humidity, the moisture content of wood is also high. The higher the moisture content is, the lower or flatter the moisture content in the middle part will be. When the seal is taken out of the drying dish, about 1% of the surface moisture content is lost. The three pictures just confirm this point. The moisture content of the wood blocks in this environment is stable between 21% and 24%, and the equilibrium moisture content has not been reached. The measured value of the equipment will gradually deviate from the measured value of the single-sided single-sided nuclear magnetic resonance, and the error value may even exceed 1%. This may be because the wood exposed to the environment loses moisture during the continuous measurement process. The maximum error values ​​in the radial, chordal, and 45° directions are 1.04%, 1.93%, and 1.30%, respectively. After each measurement of the equipment, the moisture content of the 7 layers is averaged and compared with the weighing method. The comparison errors are 0.6%, 0.637%, and 0.91%, respectively. The error in the 45-degree direction is large, which may be caused by the angle measurement error.

[0087] In another specific application, the method for determining the moisture content of wood layers further comprises:

[0088] (21) The electrode component is brought into contact with different positions in any layer of the wood to be tested, and a measurement button is triggered to obtain sampling voltage values ​​corresponding to multiple positions.

[0089] (22) For any position, the microcontroller is used to determine the corresponding wood stratification moisture content based on the preset fitting function model.

[0090] (23) The wood stratified moisture contents corresponding to multiple positions are averaged to obtain the final wood stratified moisture content.

[0091] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0092] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A device for measuring moisture content of wood layers, characterized in that: The wood layer moisture content determination device comprises an electrode component, a human-machine interaction component and a microcontroller; The electrode component is used to contact any layer of the wood to be tested, and collect voltage information of the corresponding wood layer when the measuring button is triggered; The human-machine interaction component is used to input the size value, angle value and type of the wood to be tested into the microcontroller; wherein the angle value takes the chord direction of the wood as 0 degrees; The microcontroller is connected to the electrode component and the human-computer interaction component respectively, and the microcontroller is used to: receive the voltage information and extract the sampled voltage value; receive the size value, the angle value and the type; call the corresponding preset fitting function model according to the angle value and the type; calculate the wood stratification moisture content according to the sampled voltage value, the size value and the angle value based on the preset fitting function model; wherein the preset fitting function model realizes angle compensation processing.

2. The device for measuring moisture content of wood layers according to claim 1, characterized in that: The wood layer moisture content determination device also includes a signal amplification circuit, a Schmidt trigger circuit, a timer, a logic gate circuit module and a capacitor module; One end of the positive electrode of the electrode component is connected to the input end of the signal amplifying circuit, the other end of the positive electrode of the electrode component is in contact with any layer of the wood to be tested, and the negative electrode of the electrode component is grounded; The output end of the signal amplifying circuit is connected to the Schmitt trigger circuit, and the output end of the Schmitt trigger circuit is connected to the logic gate circuit module; The timer is a monostable circuit associated with the measuring button, and the timer is used to continuously output a trigger level to the logic gate circuit module within a preset time period when the measuring button is triggered, so that the logic gate circuit module outputs a voltage within the preset time period to charge the capacitor in the capacitor module; The microcontroller is used to extract the voltage extreme value of the capacitor in the capacitor module within the preset time period and use it as the sampled voltage value.

3. The device for measuring moisture content of wood layers according to claim 2, characterized in that: The device for measuring the moisture content of wood layers also includes a display screen, a power supply and a voltage stabilizer; The display screen is connected to the microcontroller, and the display screen is used to display the size value, the angle value, the type, the sampled voltage value and the wood stratification moisture content; The power supply is connected to the voltage regulator, and the power supply supplies power to the signal amplifying circuit, the Schmitt trigger circuit and the timer through the voltage regulator.

4. The device for measuring moisture content of wood layers according to claim 1, characterized in that: When the type of the wood to be tested is poplar, the microcontroller calls the corresponding preset fitting function model according to the angle value and the type of the wood to be tested, including: The first function unit is used for: when the angle value is 90°, the corresponding preset fitting function model is: ； The second function unit is used for: when the angle value is 0°, the corresponding preset fitting function model is: ； ； MC=Z+XZ; The third function unit is used for: when the angle value is within the range of 0°-90°, the corresponding preset fitting function model is: ； ； ； ； Where h is the sampling voltage value, MC is the wood stratification moisture content, Z is the value of the first correction equation, XZ is the value of the second correction equation, is the size value, is the angle value, The moisture content value that needs to be compensated for each degree of deviation in each size and texture direction.

5. A method for determining the moisture content of wood layers, characterized in that: The method for determining the moisture content of wood layers comprises: Installing a wood layer moisture content measuring device as described in any one of claims 1 to 4; Input the size, angle and type of the wood to be tested into the microcontroller through the human-computer interaction component; Put the electrode component in contact with any layer of the wood to be tested, and trigger the measurement button; The microcontroller receives the voltage information corresponding to the wood layer after triggering and extracts the sampled voltage value, and calls the corresponding preset fitting function model according to the angle value and the type; wherein the preset fitting function model realizes the angle compensation processing; The microcontroller is used to calculate the wood stratification moisture content according to the sampled voltage value, the size value and the angle value based on the preset fitting function model.

6. The method for determining the moisture content of wood layers according to claim 5, characterized in that: The process of determining the preset fitting function model includes: Slice wood samples of any type and any angle value to obtain wood sample layers with various slice sizes; All the wood samples were layered to absorb moisture and then left to stand; For each of the wood sample layers, a plurality of sampling points are determined, and a sampling voltage value and a moisture content of the wood layer at each sampling point are measured; Based on the angle values, size values, sampling voltage values ​​of each sampling point and moisture content of the wood layers corresponding to all the wood sample layers, a nonlinear cubic polynomial is used for surface fitting, and angle compensation processing is combined to obtain a corresponding preset fitting function model.

7. The method for determining the moisture content of wood layers according to claim 6, characterized in that: The process of determining the preset fitting function model also includes: When the angle value is in the range of (0, 90), angle compensation processing is performed based on the preset fitting function model fitted when the angle value is 0 and the preset fitting function model fitted when the angle value is 90.

8. The method for determining the moisture content of wood layers according to claim 7, characterized in that: The angle compensation process is as follows: The preset fitting function model obtained when the angle value is 0 is subtracted from the preset fitting function model obtained when the angle value is 90, and then the 90-degree average is performed to obtain the moisture content value that needs to be compensated for each degree of deviation of each size and texture direction; Based on the moisture content value that needs to be compensated for each size and each degree of deviation of the texture direction, the moisture content of the wood layers with angle values ​​within the range of (0, 90) is compensated to obtain the final moisture content of the wood layers.

9. The method for determining the moisture content of wood layers according to claim 8, characterized in that: The calculation formula for the moisture content value that needs to be compensated for each degree of deviation in each size and texture direction is: ； in, The moisture content value that needs to be compensated for each degree of deviation in each size and texture direction. is the size value, h is the sampled voltage value; (Z+XZ) corresponds to the preset fitting function model obtained by fitting when the angle value is 0.

10. The method for determining the moisture content of wood layers according to claim 5, characterized in that: The method for determining the moisture content of wood layers also includes: The electrode component is brought into contact with different positions in any layer of the wood to be tested, and a measuring button is triggered to obtain sampling voltage values ​​corresponding to multiple positions; For any position, the microcontroller is used to determine the corresponding wood layer moisture content based on the preset fitting function model; The wood stratified moisture contents corresponding to multiple positions are averaged to obtain the final wood stratified moisture content.

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