CN1963478A - Method and apparatus for testing water ratio of corn - Google Patents

Abstract

The invention discloses a method and a device for detecting moisture content of grains. The detection method is to first feed the grain into a pair of pressure roller sensors that rotate in opposite directions and apply a potential difference; and obtain the time-series variation curve of the real-time resistance equivalent voltage of the grain through conversion; by analyzing the characteristic peak height of the curve or peak area, calculate the grain moisture content; and perform temperature compensation, and finally get the compensated grain moisture content. Its detection device mainly includes a pressure roller sensor, a thermometer, a measurement circuit and an output display. The invention has a large testing range, not only can measure grains with a moisture content below 23.5%, but also can measure grains with a moisture content greater than 23.5%; the detection accuracy is high, the reliability is good, and the operation is convenient; it can measure dynamic changes in temperature and moisture distribution of grains In the case of large fluctuation range, the moisture content of grain can be accurately measured.

Description

A method and device for detecting moisture content of grain

technical field

The invention relates to the field of grain detection, in particular to a method and a device for detecting the moisture content of grain.

Background technique

The precise detection technology of grain moisture content has always been a technical problem in the field of grain drying, processing and circulation. How to reliably and accurately detect the moisture content of grain is one of the key factors affecting the development of grain processing industry. At present, the detection methods of grain moisture content include microwave method, infrared method, capacitance method, neutron method and resistance method. The common disadvantage of microwave method, infrared method and capacitance method is that it is greatly affected by the shape, thickness, density and moisture distribution inside the grain. When the temperature changes greatly and the moisture distribution inside the grain fluctuates greatly, the detection of these methods The precision is lower. The biggest problem with the neutron method is that due to the unstable scattering characteristics of hydrogen, the changing law of the relationship between the neutron count ratio and the grain volumetric moisture content will vary with different grain varieties; moreover, when the neutron method is used to detect the grain moisture content Corresponding pretreatment must be done for each batch of materials, so there is no neutron grain moisture detector with good reliability and high precision at present. Now more commonly used is the resistance method to detect the moisture content of grains, which is based on the principle that the moisture in the grains will affect the conductivity of solid substances. However, the existing methods for detecting the moisture content of grains can only meet the requirements of accuracy when the moisture content of the grains is 13% to 24%, and when the moisture content of the grains is lower than 13% or higher than 24%, the existing The detection error of the method is large, and the moisture content of grain cannot be accurately measured.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings in the prior art and provide a method for detecting moisture content of grains with high measurement accuracy, good reliability and convenient operation.

Another object of the present invention is to provide a device for detecting the moisture content of grains used in the above method.

The object of the present invention is achieved through the following technical solutions:

A method for detecting the moisture content of grains, comprising the following steps: first, the grains are fed into a pair of pressure roller sensors that rotate in opposite directions and are applied with a potential difference; The sampled signal is collected and output to the impedance conversion circuit, through the conversion of the impedance conversion circuit, the signal is sent to the A/D conversion circuit to obtain the time series change curve of the real-time resistance equivalent voltage of the grain; by analyzing the time series change curve The characteristic peak height or peak area is calculated to obtain the moisture content of the grain; at the same time, the temperature change during the detection process is also measured in real time, and the calculated grain moisture content is compensated according to the temperature change, and finally the compensated grain moisture content is obtained.

When the moisture content of the grain is less than or equal to 23.5%, the moisture content of the grain is calculated by analyzing the characteristic peak height of the time-series variation curve, and the calculation formula is: $w_{\mathrm{the\; s}}\%=K_1\frac{R_{x\min }}{R_i+R_{x\min }}\mathrm{E.}+b_I$ , where: W _s % is the moisture content of the grain, K _I is the slope, R _xMin is the characteristic value of the peak height of the curve, R _I is the proportional resistance, E is the standard power supply, and b _I is the intercept.

When the moisture content of the grain is greater than 23.5%, the moisture content of the grain is calculated by analyzing the peak area of the time-series variation curve, and the calculation formula is: $w_{\mathrm{the\; s}}\%=K\×\[\underset{i=1}{\overset{N}{\mathrm{\Σ}}}(A_i\×T)/N\]+b$ , where: W _s % is grain water content, K is conversion slope coefficient, A _i is waveform feature point, T is sampling period, b is intercept, i∈(0,200). In the formula, (A _i ×T) represents the peak area of the curve.

During the detection process, the temperature change during the detection process is also measured in real time, and the calculated grain moisture content is compensated according to the intensity and direction of the temperature change. The compensation formula is w _b %=-0.0031t ² +0.1613t+20.704 , W _b % is the compensation for the impact of grain temperature changes on the measurement, and is the correction of the moisture content of the grain, and t is the grain temperature.

Finally, the compensated grain moisture content is obtained, that is, the measured moisture content is the sum of the grain moisture content calculated according to the characteristic peak height or peak area of the time-series change curve and the temperature-compensated grain moisture content. The specific calculation formula is: w%=w _s %+ w _b %, where w% is the measured grain moisture content. The potential difference applied on the pressure roller sensor is $V=\frac{R_x}{\mathrm{Ri}+R_x}\mathrm{E.}\left(V\right)$ , where R _i is the i-th proportional resistance, R _x is the resistance of the measured grain, and E is the standard power supply.

The invention adopts the resistance characteristic value characterized in the crushing process of the detected grains in the fixed gap, and obtains the time-series variation curve of the conversion voltage through an impedance transformation circuit. Because the grain is being crushed, the change law of the contact area between the grain and the pressure roller sensor is from zero to the maximum and then to the minimum. This is an upward convex curve, corresponding to the sampling circuit resistance change curve Then go through such a process from open circuit (maximum resistance) → minimum resistance (maximum moisture) → open circuit (maximum resistance); the obtained curve is a downwardly concave curve (the ordinate of the curve is the conversion voltage, and the abscissa is the time ).

A device for detecting the moisture content of grains of the above method, comprising a pressure roller sensor 1, a temperature sensor, a measurement circuit, an A/D analog-to-digital conversion unit, an operation control unit and an output display 6; the measurement circuit includes a sampling circuit, Multiple conversion circuit, impedance conversion circuit and adjustable power supply; pressure roller sensor 1 detects the sampling signal and inputs it to the sampling circuit in the measurement circuit, the sampling circuit is composed of a proportional resistance converter and a signal electrode, and the input of the proportional resistance converter is The sampling signal detected by the pressure roller sensor 1 selects a specific resistance signal through the proportional resistance and outputs it to the signal electrode, and the signal electrode outputs the extracted resistance signal to the impedance conversion circuit, and the impedance conversion circuit performs impedance conversion on the input resistance signal Form a voltage signal and output it to the A/D analog-to-digital conversion unit. After the signal is converted by A/D, it passes through the operation control unit, and the final value is sent to the output display 6; the tunable power supply is simultaneously connected with the impedance conversion circuit and the multiple conversion circuit. connected, the output of the multiplexing circuit is a sampling circuit.

The surface of the pressure roller sensor 1 is designed with texture. Pressure roller sensor 1 is a pair of cylindrical rollers processed from rustless conductive material (such as stainless steel). When measuring hulled grains such as rice and barley, in order to avoid shelling, the pressure roller sensor should preferably rotate at a constant speed. In the determination of grains such as wheat and soybeans, the pressure roller sensor is preferably rotated at a differential speed to improve the test effect.

The test device also includes a feeding disc 3 with a seed groove designed on the end face, the feeding disc 3 and the synchronizer 4 are installed on the same shaft, and gears are also installed on the shaft, and the feeding disc 3 is driven by the gears. Sampling synchronizer 4 and pressure roller sensor 1 rotate together. When the feeding disc 3 feeds material to the pressure roller sensor 1, the sampling synchronizer 4 sends out a synchronous signal. The sampling synchronizer 4 sends out a switching signal, which can be selected from Hall sensors, photoelectric sensors or contact switches; its function is to send an instruction to start detection to the detection device 5 in real time, so as to ensure that the grain information detected by the detection device 5 is accurate. correct.

The frequency-adjustable power supply of the detection circuit is composed of three-terminal adjustable integrated voltage-stabilizing power supply LM317, capacitors C1, C2, C3, constant resistor R1 and variable resistor R2. The function of the three-terminal adjustable integrated regulated power supply LM317 is to adjust the voltage of +12-25V to the power supply voltage of +10V; the function of the two capacitors C1 and C3 is to filter and improve the quality of the power supply; capacitor C2, constant resistance R1 and The function of the adjustable potentiometer R2 is to adjust the output amplitude value of the power supply.

The proportional resistance converter is composed of 3-way high-speed electronic conversion switches K1, K2, K3 and proportional resistors R3, R4, R5. Its function is to select a specific proportional resistor according to the characteristics of the input sampling signal, and use it in different water areas. automatic measurement conversion. The function of the signal electrode F is to extract the resistance signal of the grain.

The impedance conversion circuit is composed of instrumentation operational amplifier INA102, capacitors C6, C7, adjustable potentiometers R6, R9, resistors R8, R10, R11 and integrated operational amplifier OP27. Among them, the instrument operational amplifier INA102 is used to improve the input impedance of the signal acquisition unit, the adjustable potentiometer R6 is used to adjust the polarity of the output voltage, the capacitors C6 and C7 are decoupling capacitors, and the integrated operational amplifiers OP27, R8, R9, The overall function of R10 and R11 is to adjust the zero position of the impedance conversion circuit.

The A/D analog-to-digital conversion unit is composed of an arithmetic controller AD8x.

The output display 6 is a window for man-machine dialogue, and a touch screen or LCD display screen can be selected.

Compared with the prior art, the present invention has the following advantages and effects:

(1) The test range of the present invention is large, not only can measure the grain with moisture content below 23.5%, but also can measure the grain with moisture content greater than 23.5%.

(2) The detection accuracy of the present invention is high, the reliability is good, and the operation is convenient.

(3) The present invention can accurately measure the moisture content of the grain under the condition that the dynamic temperature changes and the moisture distribution of the grain varies widely.

(4) The device of the present invention is simple and convenient for detection.

Description of drawings

Figure 1 is a structural diagram of the pressure roller sensor.

Fig. 2 is a functional block diagram of the test circuit of the present invention.

FIG. 3 is a circuit diagram of Embodiment 1. FIG.

Fig. 4 is the measured voltage timing diagram under different moisture.

Fig. 5 is a time curve diagram of the switching voltage measured by the embodiment of the present invention.

Fig. 6 is the compensation curve of rice moisture content and temperature change.

Fig. 7 is a functional schematic diagram of the detection device.

Detailed ways

The present invention will be described in further detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto.

The end surface of the feeding disc 3 is provided with a seed-receiving groove, and the feeding disc rotates in the longitudinal section during detection, and the grains are sent to the two pressure roller sensors 1 one by one by the seed-receiving grooves evenly distributed on the outer end surface of the feeding disc. between.

As shown in Figure 1, the pressure roller sensor 1 is a pair of cylindrical rollers processed from stainless steel. During the measurement, the two pressure roller sensors 1 rotate inwardly, and the two pressure roller sensors are two electrodes, and the potential difference applied thereon is $V=\frac{R_x}{R_i+R_x}\mathrm{E.}\left(V\right)$ , where R _i is the i-th proportional resistance, R _X is the resistance of the rice under test, and E is the standard power supply.

When the paddy falls between the two pressure roller sensors from the feeding disc, due to the existence of the paddy, the two electrodes are connected, so that the two electrodes form a closed loop (see Figure 3), and the paddy is gradually pressed During the crushing process, the resistance signal is transmitted from one end of the pressure roller sensor, and is converted by the impedance conversion circuit as shown in Figure 3, and then sent to the A/D conversion circuit to obtain the real-time resistance equivalent voltage of the rice to be tested during the sampling process. Timing change curve (as shown in Figure 5). The invention adopts the resistance characteristic value characterized in the process of detecting rice crushing in a fixed gap, and obtains the time curve of the conversion voltage through an impedance conversion circuit. Because during the process of rice being crushed, the change law of the contact area between the rice and the pressure roller sensor changes from zero to the maximum and then to the minimum. This is an upward convex curve, corresponding to the resistance change curve of the sampling circuit Then go through such a process from open circuit (maximum resistance) → minimum resistance (maximum moisture) → open circuit (maximum resistance); the obtained curve is a downwardly concave curve (the ordinate of the curve is the conversion voltage, and the abscissa is the time ) as shown in Figure 4 and Figure 5. Figure 4 is a typical cluster of curves representing various curves of grain moisture from 13.7% to 31.7%. Figure 5 is a typical curve for grain moisture at 21%.

When the moisture content of rice is less than or equal to 23.5%, the characteristic peak height of the measured time-series variation curve (Fig. 4), that is, the ordinate value of the lowest point of the curve, calculates the moisture content of the grain, and the calculation formula is: $w_{\mathrm{the\; s}}\%=K_I\frac{R_{x\min }}{R_i+R_{x\min }}\mathrm{E.}+b_I$ ; Among them: K _I - slope, R _i - proportional resistance, R _Xmin - characteristic value of peak height, b _I - intercept, E - standard power.

When the moisture content of the grain is greater than 23.5%, it is calculated by the peak area of the measured time-series change curve (Figure 4), that is, the area surrounded by a certain curve in Figure 5 or Figure 4 and the abscissa (time coordinate). The moisture content of grain, the calculation formula is: $w_{\mathrm{the\; s}}\%=K\×\[\underset{i=1}{\overset{N}{\mathrm{\Σ}}}(A_i\×T)/N\]+b$ ; Among them: w _s % - measured rice moisture, T - collection point period, K - conversion slope coefficient, b - intercept, A _i - waveform feature point. i ∈ (0, 200).

According to the intensity and direction of temperature and rice temperature changes in the measurement and detection process as shown in Figure 6, the calculated grain moisture content is calculated according to w _b %=-0.0031t ² +0.1613t+20.704 [t in the note is After the calculation formula of temperature of paddy (°C)] is compensated, the real moisture content of paddy can be obtained, that is, w%=w _s %+w _b %, wherein: w% of the real moisture content of paddy.

Claims (10)

1, a kind of method that detects cereal moisture percentage is characterized in that comprising the steps: at first cereal being sent in a pair of pressure roller sensor that rotates and be applied with electric potential difference in opposite directions; Then in the extruded process of cereal, by described pressure roller sensor acquisition to sampled signal and output to impedance inverter circuit, through the conversion of impedance inverter circuit, signal is sent into the A/D change-over circuit, obtain the timing variations curve of the real-time equivalent resistance voltage of described cereal; By resolving the feature peak height or the peak area of described timing variations curve, calculate cereal moisture percentage; Also measure the temperature variation in the testing process simultaneously in real time, the described cereal moisture percentage that calculates is compensated the cereal moisture percentage after being compensated at last according to temperature variations.

2, the method for detection cereal moisture percentage according to claim 1 is characterized in that: when cereal moisture percentage is less than or equal to 23.5%, calculate cereal moisture percentage by the feature peak height of resolving described timing variations curve, computing formula is: $W_s\%=K_I\frac{R_{X\min }}{R_i+R_{X\min }}E+b_I$ , wherein: W _s% is cereal moisture percentage, K _IBe slope, R _XMinPeak height eigenwert, R for curve _IFor proportion resistor, E are reference power supply, b _IBe intercept; When cereal moisture percentage greater than 23.5% the time, obtain cereal moisture percentage by the calculated by peak area of resolving described timing variations curve, computing formula is: $w_s\%=K\×\[\underset{i=1}{\overset{N}{\mathrm{\Σ}}}(A_i\×T)/N\]+b,$ Wherein: W _s% is that cereal moisture percentage, K are conversion slope coefficient, A _iFor waveform character point, T for adopt dot cycle, b is intercept, i ∈ (0,200).In the formula, (A _i* T) represent the peak area of curve.

3, the method for detection cereal moisture percentage according to claim 1 and 2, it is characterized in that: in testing process, also measure the temperature variation in the testing process in real time, according to the intensity and the direction of temperature variation the described cereal moisture percentage that calculates is compensated, compensation formula is w _b%=-0.0031t ²+ 0.1613t+20.704, W _b% is that grain temperature changes the compensation that measurement is impacted, and is the correction to cereal moisture percentage, and t is a grain temperature.

4, the method for detection cereal moisture percentage according to claim 1 is characterized in that: the electric potential difference that applies on the described pressure roller sensor is $V=\frac{R_X}{\mathrm{Ri}+R_X}E\left(V\right),$ Wherein Ri is i road proportion resistor, R _XFor resistance, the E of tested cereal is reference power supply.

5, a kind of device that is used for the detection cereal moisture percentage of aforesaid right requirement 1～4 each described method is characterized in that comprising pressure roller sensor, temperature sensor, metering circuit, A/D AD conversion unit, Operations Analysis and Output Display Unit; Described metering circuit comprises sample circuit, multi-channel conversion circuit, impedance inverter circuit and tunable power supply; The pressure roller sensor is to sampled signal and be input to sample circuit in the metering circuit, sample circuit is made up of proportion resistor converter and signal electrode, the proportion resistor converter be input as the sampled signal that the pressure roller sensor arrives, select specific resistance signal and output to signal electrode through proportion resistor, signal electrode outputs to impedance inverter circuit with the resistance signal that extracts, impedance inverter circuit carries out the resistance signal of input to form voltage signal and output to the A/D AD conversion unit after the impedance transformation, signal by Operations Analysis, is transported to Output Display Unit with the numerical value that obtains at last through A/D conversion back; Tunable power supply is connected with multi-channel conversion circuit with impedance inverter circuit simultaneously, and multi-channel conversion circuit is output as sample circuit.

6, the device of detection cereal moisture percentage according to claim 5 is characterized in that: comprise that also an end face is provided with the feeding disk of seed bearing groove, feeding disk and sample-synchronous device, gear are installed on the same axis.

7, the device of detection cereal moisture percentage according to claim 5 is characterized in that: the Frequency Adjustable power supply of described testing circuit can be adjusted integrated regulated power supply LM317, capacitor C 1, C2, C3, be decided resistance R 1 and variohm R2 constitutes by three ends.

8, the device of detection cereal moisture percentage according to claim 5 is characterized in that: described proportion resistor converter is made up of 3 road high-velocity electrons switch K1, K2, K3 and proportion resistor R3, R4, R5.

9, the device of detection cereal moisture percentage according to claim 5 is characterized in that: described impedance inverter circuit is made up of with operational amplifier INA102, capacitor C 6, C7, adjustable potentiometer R6, R9, resistance R 8, R10, R11 and integrated operational amplifier OP27 instrument.

10, the device of detection cereal moisture percentage according to claim 5 is characterized in that: described A/D AD conversion unit is made of arithmetic and control unit AD8x.

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