CN100460859C - Optical Fiber Sensing Infrared Moisture Meter - Google Patents

Abstract

An optical fiber sensing infrared moisture meter, including power supply, CPU and peripheral circuits connected to it: display module, keyboard and analog-to-digital converter (A/D), LED drive circuit, measurement LED (D2), reference LED (D1), dual transmit fiber bundle (1), receive fiber bundle (2), photodiode (D3) and lock-in amplifier. The transmitting-receiving optical fiber bundle is used as the measuring sensing optical path, the structure is simple, and the manufacturing cost is low. The circuit has strong anti-interference ability, and the measurement LED (D2) and the reference LED (D1) are driven by a square wave signal with a duty ratio of 1:1, so that the measurement LED (D2) and the reference LED (D1) emit alternating light intensity. The optical signal irradiates the sample to be tested, so that the photodiode (D3) outputs the AC measured signal, and performs active band-pass filtering on the AC measured signal to suppress noise, perform AC amplification, and DC demodulation to improve Signal-to-noise ratio, high gain and high sensitivity at the same time, greatly improving measurement accuracy.

Description

Optical Fiber Sensing Infrared Moisture Meter

technical field

The invention relates to an optical fiber sensing infrared moisture meter, which belongs to the technical field of electronic moisture measuring instruments.

Background technique

Compared with the classic 105°C constant weight method, the infrared measurement method is one of several rapid measurement methods. Its principle is to use the moisture contained in the measured substance to absorb infrared light of a specific wavelength. Different moisture corresponds to different absorption light intensities. Thus, the relationship between light intensity and moisture is obtained. At present, domestic infrared moisture meters use tungsten filament lamps with high luminous power and spectral line width as light sources, and then use spectroscopic devices such as monochromatic filters or gratings to filter out moisture absorption wavelengths and a series of reference wavelengths for measurement. Internationally, the 9100 whole-grain near-infrared rapid tester produced by Sweden's Perten Instrument Company can measure six kinds of moisture, protein, and fat in the seeds of grain and oil crops such as wheat, corn, soybean, and rapeseed. Composition, the principle is to use a wide-spectrum light source to measure the material composition by obtaining the reflected light intensity of various components after the sample is reflected and the grating is split. It can measure the whole sample without crushing, and can quickly measure 120 samples within 1 minute. The disadvantage of the background technology is that the structure of the optical path is complicated and the manufacturing cost is expensive.

Contents of the invention

The object of the present invention is to introduce a fiber optic sensor type infrared moisture meter, which has the advantages of adopting general amplifying circuit for signal processing circuit, simple optical path structure and low manufacturing cost.

In order to achieve the above object, the present invention adopts the following technical solutions. Now in conjunction with accompanying drawing, explain as follows.

An optical fiber sensing infrared moisture meter, including a power supply, a CPU and peripheral circuits connected to it: a display module, a keyboard and an analog-to-digital converter A/D, and the positive and negative voltage output terminals of the power supply are VCC and ground respectively line, the output end of the analog-to-digital converter A/D is connected to the I/O port of the CPU, and the ROM inside the CPU stores a program that commands the CPU to perform the following operations. The operations include directing the keyboard to work and controlling the following The LED drive circuit drives the following measurement LEDD2 and the following reference LEDD1 to emit light alternately, accepts the infrared sensor signal output by the analog-to-digital converter A/D and converts it into a digital quantity, and directs the display module Display measurement results, characterized in that it also contains LED drive circuit, measurement LED D2, reference LED D1, dual emission fiber optic bundle 1, receiving fiber optic bundle 2, photodiode D3 and lock-in amplifier, measurement LEDD2 and reference LEDD1 emission light The wavelengths are 1450nm and 1310nm respectively, and the dual-emitting fiber bundle 1 and the receiving fiber bundle 2 form a transmitting-receiving fiber bundle. Combined with the incident end of the receiving fiber bundle 2 to form a circular emission-receiving surface, the emission-receiving surface is perpendicular to the optical axis of the emission-receiving fiber bundle, and the optical fiber in the output end of the double emission fiber bundle 1 Randomly distributed and arranged in a circular emission light exit surface 12, as the central part of the emission-receiving surface, the optical fibers in the incident end of the receiving fiber bundle 2 are randomly distributed and arranged in a circular light reception surface 20, as In the peripheral part of the transmitting-receiving surface, the optical fibers forming the double-emitting optical fiber bundle 1 are randomly divided into two sub-beams 10, 11 at the incident end of the emitting light of the double-emitting optical fiber bundle 1, and the two sub-beams 10, 11 Two incident surfaces: the measuring light incident surface 14 and the reference light incident surface 13 are respectively perpendicular to the optical axes of the two split beams 10, 11, the measuring light incident surface 14 and the reference light incident surface 13 are aligned with the measuring LED D2 and the reference light incident surface respectively The light-emitting surface of LED D1 is close to the light-emitting surface of measuring LED D2 and reference LED D1, and there is a receiving light emitting surface 21 at the receiving light emitting end of receiving optical fiber bundle 2, and the receiving light emitting surface 21 is connected to receiving optical fiber bundle 2. The optical axis is vertical, the receiving light emitting surface 21 is closely attached to the photosensitive surface of the photodiode D3 in a manner of aligning with the photosensitive surface of the photodiode D3, and the measurement LED D2 and the reference LED D1 are respectively connected to the measurement LED D2 output terminal and the reference LED driving circuit. The output terminal of the LED D1 is connected, the output terminal of the photodiode D3 is connected with the input terminal of the lock-in amplifier, and the output terminal of the lock-in amplifier is connected with the input terminal of the analog-to-digital converter A/D.

When measuring the moisture contained in the sample 30 to be tested, the transmitting-receiving surface is placed at a distance of 5-15 mm from the surface of the sample 30 to be tested in a manner aligned with the surface of the sample 30 to be tested. The sample 30 to be tested can be rice, paper, wood, shredded tobacco, tea, coffee and the like.

Compared with the background technology, the infrared moisture meter of the present invention has the following advantages:

(1) Replace the traditional sensing optical path with the transmitting-receiving optical fiber bundle

The traditional infrared moisture meter uses a light source with a wide emission line and a filter or a grating to form an emission-reception optical path, that is, a measurement and sensing optical path, which is not only complex in structure but also expensive. The infrared moisture meter of the present invention adopts the transmitting-receiving optical fiber bundle as the transmitting-receiving optical path, that is, the measuring and sensing optical path, which not only simplifies the structure of the measuring and sensing optical path, but also greatly reduces the manufacturing cost of the sensing optical path.

(2) The circuit has strong anti-interference ability

The measured signal is a weak electrical signal submerged by noise, and it is difficult to amplify it effectively by general methods. The infrared moisture meter of the present invention applies the principle of lock-in amplification, drives the measurement LED D2 and the reference LED D1 with a square wave signal with a duty ratio of 1:1, and makes the measurement LED D2 and the reference LED D1 emit light signals with alternating light intensity. Irradiate the sample to be tested, make the photodiode D3 output the AC measured signal, suppress the noise by performing active band-pass filtering on the AC measured signal, perform AC amplification, DC demodulation, improve the signal-to-noise ratio, and at the same time Obtain high gain and high sensitivity, and greatly improve measurement accuracy.

Description of drawings

Fig. 1 is a structural block diagram of the optical fiber sensing infrared moisture meter of the present invention.

Fig. 2 is the optical fiber sensing optical path structure and the placement position of the sample disk of the optical fiber sensing infrared moisture meter of the present invention.

Figure 3 is a cross-sectional view of the transmit-receive fiber optic bundle.

Fig. 4 is a circuit diagram of the optical fiber sensing infrared moisture meter of the present invention.

Detailed ways

The optical fiber sensing infrared moisture meter and working principle of the present invention will now be described in detail in conjunction with the accompanying drawings and embodiments.

Example:

This embodiment has exactly the same structure as the above-mentioned optical fiber sensing infrared moisture meter, and its further feature is that the LED drive circuit includes a first integrated circuit U1, a second integrated circuit U2, a third integrated circuit U3, a measurement LEDD2, a reference LED D1, the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the first capacitor C1, the second capacitor C2 and the first transistor T1, the first integrated circuit U1, the The models of the second integrated circuit U2 and the third integrated circuit U3 are NE555, 74LS74 and MAX4624 respectively, the models of the measuring LED D2 and the reference LED D1 are L7850-01 and L7866 respectively, the first resistor R1, the second resistor R2, and the third resistor R3 , The resistance values of the fourth resistor R4 and the fifth resistor R5 are 1KΩ, 2KΩ, 1KΩ, 1KΩ, 1KΩ respectively, the capacitances of the first capacitor C1 and the second capacitor C2 are 0.01μF and 100PF respectively, and the model of the first transistor T1 It is 9014, the first pin of the first integrated circuit U1 is grounded, the second pin of the first integrated circuit U1 is connected to the sixth pin, the fourth pin of the first integrated circuit U1 is connected to the eighth pin and then connected to the VCC terminal, and the first A capacitor C1 is connected between the fifth pin of the first integrated circuit U1 and the ground, the sixth pin of the first integrated circuit U1 is connected to the second pin, and the second capacitor C2 is connected across the first integrated circuit U1. Between pin 6 and the ground wire, the first resistor R1 is connected between the pin 6 of the first integrated circuit U1 and the pin 7 of the first integrated circuit U1, and the second resistor R2 is connected across the pin 7 of the first integrated circuit U1. Between the 7th pin and the VCC terminal, the 14th pin and the 7th pin of the second integrated circuit U2 are respectively connected to the VCC terminal and the ground wire, the 2nd pin of the second integrated circuit U2 is connected to the 6th pin, and the first integrated circuit U2 The third pin of U1 is connected to the third pin of the second integrated circuit U2, the emitter of the first transistor T1 is grounded, and the third resistor R3 is connected across the fifth pin of the second integrated circuit U2 and the base of the first transistor T1 Between them, the collector of the first transistor T1 is respectively connected to the negative pole of the measuring LEDD2 and the negative pole of the reference LED D1, the positive pole of the measuring LEDD2 is connected to the fourth pin of the third integrated circuit U3 through the fourth resistor R4, and the positive pole of the reference LED D1 The fifth resistor R5 is connected to the sixth pin of the third integrated circuit U3, the first pin of the third integrated circuit U3 is connected to the P1.2 pin of the CPU through the J1 terminal, the second pin of the third integrated circuit U3 is connected to the fifth After the pin is connected, it is connected to the VCC terminal, and the third pin of the third integrated circuit U3 is grounded; the lock-in amplifier includes a photodiode D3, a fourth integrated circuit U4, a fifth integrated circuit U5, a sixth integrated circuit U6, a seventh integrated circuit U7, The eighth integrated circuit U8, the ninth integrated circuit U9, the tenth integrated circuit U10, the eleventh integrated circuit U11, the sixth resistor R6, the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the tenth resistor R10, The eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13, The fourteenth resistor R14, the fifteenth resistor R15, the sixteenth resistor R16, the third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6, the seventh capacitor C7, the eighth capacitor C8, the ninth capacitor Capacitor C9 and tenth capacitor C10, the type of photodiode D3 is G8422-03, the fourth integrated circuit U4, the fifth integrated circuit U5, the sixth integrated circuit U6, the seventh integrated circuit U7, the eighth integrated circuit U8, the ninth integrated circuit The models of the integrated circuit U9, the tenth integrated circuit U10, and the eleventh integrated circuit U11 are LF356, AD829, AD829, AD829, AD829, OP177, CD4066, and CD4069 respectively; the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 The resistance values of the ninth resistor R9, the tenth resistor R10, the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13, the fourteenth resistor R14, the fifteenth resistor R15, and the sixteenth resistor R16 are respectively It is 200K, 2KΩ, 2KΩ, 2KΩ, 10KΩ, 2K, 30KΩ, 2KΩ, 2KΩ, 2KΩ, 3KΩ, the third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6, the seventh capacitor C7, the eighth capacitor The capacitances of capacitor C8, ninth capacitor C9, and tenth capacitor C10 are 0.01μF, 3300PF, 0.01μF, 1000PF, 0.01μF, 0.01μF, 0.01μF, 1μF, 0.01μF, and the anode and cathode of photodiode D3 are respectively connected to The second pin of the fourth integrated circuit U4 is connected to the ground wire, the third pin of the fourth integrated circuit U4 is grounded, the sixth resistor R6 is connected between the second pin and the sixth pin of the fourth integrated circuit U4, and the fifth The third pin of the integrated circuit U5 is grounded, the fourth capacitor C4 is connected in parallel with the eighth resistor R8 and connected between the second pin and the sixth pin of the fifth integrated circuit U5, and the third capacitor C3 is connected in series with the eighth resistor R8 It is connected between the 6th pin of the fourth integrated circuit U4 and the 2nd pin of the fifth integrated circuit U5, the 3rd pin of the sixth integrated circuit U6 is grounded, and the sixth capacitor C6 is connected in parallel with the tenth resistor R10 and then connected across the Between the 2nd pin and the 6th pin of the sixth integrated circuit U6, the fifth capacitor C5 and the ninth resistor R9 are connected in series between the 6th pin of the fifth integrated circuit U5 and the 2nd pin of the sixth integrated circuit U6 Between, the third pin of the seventh integrated circuit U7 is grounded, the twelfth resistor R12 is connected between the second pin and the sixth pin of the seventh integrated circuit U7, and the seventh capacitor C7 is connected in series with the eleventh resistor R11 to cross the Connected between pin 6 of the sixth integrated circuit U6 and pin 2 of the seventh integrated circuit U7, pin 3 of the eighth integrated circuit U8 is grounded, and the ninth capacitor C9 is connected in parallel with the fourteenth resistor R14 and connected across the Between pin 2 and pin 6 of the eighth integrated circuit U8, the eighth capacitor C8 and the thirteenth resistor R13 are connected in series across pin 6 of the seventh integrated circuit U7 and pin 2 of the eighth integrated circuit U8 Between, the third pin of the ninth integrated circuit U9 is grounded, and the tenth capacitor C10 is connected across the first Between pin 2 of the ninth integrated circuit U9 and the ground wire, the eleventh capacitor C11 and the sixteenth resistor R16 are connected in parallel and connected between pin 2 and pin 6 of the ninth integrated circuit U9, and the tenth integrated circuit The 12th pin and the 6th pin of U10 are respectively connected with the 1st pin and the 2nd pin of the eleventh integrated circuit U11, and the 6th pin of the seventh integrated circuit U7 and the 6th pin of the eighth integrated circuit U8 are connected with the 10th integrated circuit U8 respectively. The 8th pin of the integrated circuit U10 is connected to the 10th pin, the 9th pin of the tenth integrated circuit U10 is connected to the 11th pin, and the fifteenth resistor R15 is connected across the 2nd pin of the ninth integrated circuit U9 and the tenth integrated circuit Between pin 9 of U10, pin 5 of the second integrated circuit U2 is connected to pin 1 of the eleventh integrated circuit U11, pin 6 of the ninth integrated circuit U9 is connected to the input end of the analog-to-digital converter A/D connect.

working principle

The water in the substance has a strong absorption band at the infrared wavelength of 1450nm. Therefore, when the near-infrared light with a wavelength of 1450nm is irradiated on the tested sample, part of the light will be absorbed by the tested sample, and the other part will be reflected by it. Therefore, as long as the intensity of the incident light, reflected light and diffuse reflected light is measured, the water content information of the tested sample can be obtained.

According to the Kubelka-Munk theory, we get

$\mathrm{<span\; class="notranslate">\; ln</span>}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; K</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

where R is the reflectance of the sample, K is the absorption coefficient, S is the scattering coefficient, and B is a constant.

Within a certain range of light intensity, the relationship between the absorption coefficient K and the water content C contained in the measured sample is as follows:

K＝ε*C (3-2)

where ε is a constant of proportionality.

Considering the definition of the reflectance R of the tested sample:

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; I</span>}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, I ₀ is the intensity of the incident light, and I is the intensity of the reflected light.

Substituting (3-2) and (3-3) into (3-1) formula, we get

$\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; B</span>}$

The moisture C contained in the tested sample can be obtained by the following formula:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; )</span>\frac{\mathrm{<span\; class="notranslate">\; S</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}$

Therefore, as long as the values of I, _I0 and S are measured, the moisture contained in the tested sample can be measured.

When measuring the moisture contained in the sample to be tested, the emission-receiving surface of the infrared moisture meter of the present invention is aimed at the surface of the sample to be tested, and the distance between the two is 5-15mm. The infrared moisture meter of the present invention uses a dual-wavelength reflective infrared detection method to measure the moisture contained in the sample to be tested. The CPU controls the LED drive circuit to work, and drives the measurement LED D2 and reference LED D1 respectively connected to the measurement LED output terminal and the reference LED output terminal of the LED drive circuit to emit infrared light alternately. The wavelengths of the infrared light emitted by the measurement LED D2 and the reference LED D1 are 1450nm and 1310nm, respectively. The emitted infrared light 15 emitted by the measuring LED D2 and the reference LED D1 passes through two incident surfaces at the incident end of the double emission fiber optic bundle 1: a measuring light incident surface 13 and a reference light incident surface 14, two split beams 10, 11 and a double The transmitting optical fiber bundle 1 is guided to the circular transmitting-receiving surface to irradiate the measured sample 30 in the sample disc 3 . The reflected infrared light 22 reflected by the sample 30 to be tested passes through the circular light-receiving incident surface 20 and the receiving optical fiber bundle 2 , and then is transmitted to the light-receiving exit surface 21 to irradiate the photosensitive surface of the photodiode D3 . The photosensitive surface of the photodiode D3 converts the received reflected infrared light 22 into an electrical signal, outputs it from its output terminal, and adds it to the input terminal of the lock-in amplifier. The reflected infrared light 22 received by the photodiode D3 is a weak modulated optical signal, and the photodiode D3 converts it into a weak modulated electrical signal through photoelectric conversion, which is used as the input signal of the lock-in amplifier. The input signal is an analog signal. The lock-in amplifier performs band-pass filtering, demodulation and amplification on the input signal. The lock-in amplifier sends the amplified output signal to the input of the analog-to-digital converter A/D. The analog-to-digital converter A/D converts the analog signal at its input end into a digital signal, outputs it from its output end, and transmits it to the I/O port of the CPU. The CPU uses the input digital signal to calculate the water contained in the sample 30 to be measured. The CPU controls the display module to display the moisture contained in the tested sample 30 .

The infrared moisture meter of the present invention needs to be calibrated first before use. Now take the tested sample 30 as rice as an example to illustrate it. Take 10g of paddy and prepare a standard sample containing a certain amount of water by standard drying method. Then put the standard sample into the sample pan 3 of the instrument, and use the infrared moisture meter of the present invention to measure the moisture contained in the standard sample. The measurement process is as follows: See Figure 1 and Figure 4. After the power is turned on, the first integrated circuit U1 (555 time base circuit) generates an electrical pulse signal with a frequency of 20kHz. The signal is frequency-divided by the subsequent second integrated circuit U22, and the output terminal of the second integrated circuit U2 outputs a square wave signal with a frequency of 10 KHz and a duty ratio of 1:1. The square wave signal is used as a modulation signal, and is added to the base of the first transistor T1 (9014) through the third resistor R3. The collector of the first transistor T1 is connected to two light-emitting diodes: the negative pole of the measurement LEDD2 and the reference LED D1, the voltage VCC (5V) is added to the positive pole of the measurement LEDD2 and the reference LED D1 through the third integrated circuit U3 (MAX4624), and the third The integrated circuit U3 is a two-to-one switch, so that no matter which light-emitting diode is working, the infrared light emitted by them is a modulated light signal with a frequency of 10KHz, and the third integrated circuit U3 can be controlled by the CPU to select which of the two light-emitting diodes a job. After the measurement key is pressed, the CPU controls the measurement LED D2 and the reference LED D1 to work alternately through the first pin of the third integrated circuit U3, and irradiates the measured sample 30 through the emitting optical fiber bundle 1. First make the reference LED D1 work, after the photodiode D3 receives the infrared light emitted by the reference LED D1, it converts it into a weak photocurrent, after the photocurrent is amplified by the fourth integrated circuit U4, its output is a voltage signal, because The voltage signal is a weak signal submerged by noise, so in order to obtain the required 10KHz electrical signal, after the fourth integrated circuit U4, two levels of active strips composed of the fifth integrated circuit U5 and the sixth integrated circuit U6 are connected. A pass filter is designed to selectively amplify useful signals. The output terminal of the second-stage active bandpass filter is connected to the seventh integrated circuit U7, and its output and the output of the eighth integrated circuit U8 are respectively connected to one end of two switches of the tenth integrated circuit U10 (CD4066). The other end is connected and connected to a low-pass filter composed of the ninth integrated circuit U9, and its control gate signal is a modulated square wave signal and its inverse signal. The inverted signal is provided by the output terminal of the eleventh integrated circuit U11. The electronic switch is used as a multiplier to multiply the filtered useful signal by the reference electrical signal to obtain the sum of each harmonic component of the useful signal, and the sum of these harmonic components enters the low-pass filter of the ninth integrated circuit U9 , the high-frequency component is filtered out, and only the DC voltage component proportional to the output electrical signal of the receiving photodiode D3 remains, and the strength of the output electrical signal of the photodiode D3 is proportional to the water content of the tested sample, Therefore, the DC component is directly proportional to the moisture contained in the sample to be tested. The signal is converted by the analog-to-digital converter A/D, and the voltage digital value corresponding to the reference light-emitting diode can be obtained in the CPU. Then make the measurement LEDD2 work, and the corresponding voltage digital quantity of the measurement LED can also be obtained in the same way. Comparing these two voltage digital quantities, that is, measuring voltage digital quantity/reference voltage digital quantity, a ratio can be obtained. Since the moisture contained in the measured sample is known during the calibration stage, the above ratio corresponds to a known moisture value. Through the measurement of standard samples containing different moisture, a group of corresponding ratios can be obtained and a relationship curve of moisture value-ratio can be drawn, and the curve can be fitted to obtain the function expression of the curve, and It is solidified in the ROM inside the CPU.

When the user is in use, put the paddy with unknown moisture content into the sample tray 3, start the power supply, and press the measurement key, a ratio corresponding to the measured paddy can be obtained in the CPU, and this ratio is substituted into the In the established functional relationship, the moisture value can be obtained, and then the measured moisture value is displayed on the display. One measurement is all it takes.

If it is necessary to measure the moisture contained in other substances such as wood, paper, coffee, etc., then the same as rice, at first the infrared moisture meter of the present invention is calibrated according to the standard sample, and the functional relationship is established and solidified in the ROM in the CPU , and then measure the tested sample with unknown moisture content, and display the measurement result on the display.

Claims (2)

1. A kind of optical fiber sensing type infrared moisture meter, contains power supply, CPU and the peripheral circuit connected thereon: display module, keyboard and analog-to-digital converter (A/D), the positive and negative voltage output terminals of power supply are respectively VCC terminal and ground wire, the output terminal of analog-to-digital converter (A/D) is connected with the I/O port of CPU, and the program that orders CPU to carry out following operation is stored in the ROM inside CPU, and described operation comprises command keyboard Work, control the following LED drive circuit to drive the following measurement LED (D2) and the following reference LED (D1) to emit light alternately, accept the analog-to-digital converter (A/D) output output by the analog-to-digital converter ( A/D) is converted into digital infrared sensing signals, and the command display module displays the measurement results. It is characterized in that it also contains LED drive circuits, measurement LEDs (D2), reference LEDs (D1), and dual emission fiber bundles (1 ), receiving optical fiber bundle (2), photodiode (D3) and lock-in amplifier, the wavelengths of the emitted light of the measuring LED (D2) and reference LED (D1) are 1450nm and 1310nm respectively, and the double emitting optical fiber bundle (1) and receiving optical fiber Bundle (2) constitutes the transmitting-receiving optical fiber bundle, and the optical fibers forming the dual emitting optical fiber bundle (1) and receiving optical fiber bundle (2) are all glass optical fibers, and the outgoing end of the dual emitting optical fiber bundle (1) and the receiving optical fiber bundle (2) The incident ends are combined into a circular emission-reception surface, the emission-reception surface is perpendicular to the optical axis of the emission-reception fiber bundle, and the optical fibers in the exit ends of the double emission fiber bundle (1) are randomly distributed and arranged Circular emission light exit surface (12), as the central part of the emission-reception surface, the optical fibers in the incident end of the receiving optical fiber bundle (2) are randomly distributed and arranged in a circular light reception surface (20 ), as the peripheral part of the launch-receiving surface, the optical fiber forming the double launch fiber bundle (1) is randomly divided into two sub-bundles (10,11) at the launch light incident end of the double launch fiber bundle (1) , the two incident surfaces of the two split beams (10, 11): the measuring light incident surface (14) and the reference light incident surface (13) are respectively perpendicular to the optical axes of the two split beams (10, 11), and the measuring light incident surface The surface (14) and the reference light incident surface (13) are in close contact with the light-emitting surfaces of the measurement LED (D2) and the reference LED (D1) in a manner respectively aligned with the light-emitting surfaces of the measurement LED (D2) and the reference LED (D1), There is a receiving light emitting surface (21) at the receiving light emitting end of the receiving optical fiber bundle (2), the receiving light emitting surface (21) is perpendicular to the optical axis of the receiving optical fiber bundle (2), and the receiving light emitting surface (21) is opposite to The photosensitive surface of the quasi-photodiode (D3) is in close contact with the photosensitive surface of the photodiode (D3), and the measurement LED (D2) and the reference LED (D1) are respectively connected to the output terminal of the measurement LED (D2) and the reference LED of the LED drive circuit. (D1) is connected to the output end, the output end of the photodiode (D3) is connected to the input end of the lock-in amplifier, and the output end of the lock-in amplifier is connected to the input end of the analog-to-digital converter (A/D). 2. The optical fiber sensor type infrared moisture meter according to claim 1, is characterized in that, the LED drive circuit contains the first integrated circuit (U1), the second integrated circuit (U2), the third integrated circuit (U3), the first A resistor (R1), a second resistor (R2), a third resistor (R3), a fourth resistor (R4), a fifth resistor (R5), a first capacitor (C1), a second capacitor (C2) and a first Transistor (T1), first integrated circuit (U1), second integrated circuit (U2) and third integrated circuit (U3) type are NE555, 74LS74 and MAX4624 respectively, measurement LED (D2) and reference LED (D1) The models are L7850-01 and L7866 respectively. The resistance values of the first resistor (R1), the second resistor (R2), the third resistor (R3), the fourth resistor (R4), and the fifth resistor (R5) are 1KΩ, 2KΩ, 1KΩ, 1KΩ, 1KΩ, the capacitances of the first capacitor (C1) and the second capacitor (C2) are 0.01μF and 100PF respectively, the model of the first transistor (T1) is 9014, and the capacitance of the first integrated circuit (U1) The first pin is grounded, the second pin of the first integrated circuit (U1) is connected to the sixth pin, the fourth pin of the first integrated circuit (U1) is connected to the eighth pin and then connected to the VCC terminal, and the first capacitor (C1) Connect between the 5th pin of the first integrated circuit (U1) and the ground wire, connect the 6th pin of the first integrated circuit (U1) to the 2nd pin, and connect the second capacitor (C2) across the first integrated circuit Between the 6th pin of (U1) and the ground wire, the first resistor (R1) is connected between the 6th pin of the first integrated circuit (U1) and the 7th pin of the first integrated circuit (U1), and the second The resistor (R2) is connected between the 7th pin of the first integrated circuit (U1) and the VCC terminal, the 14th pin and the 7th pin of the second integrated circuit (U2) are respectively connected to the VCC terminal and the ground wire, and the second The 2nd pin of the integrated circuit (U2) is connected to the 6th pin, the 3rd pin of the first integrated circuit (U1) is connected to the 3rd pin of the second integrated circuit (U2), and the emitter of the first transistor (T1) is grounded , the third resistor (R3) is connected between the 5th pin of the second integrated circuit (U2) and the base of the first transistor (T1), and the collector of the first transistor (T1) is respectively connected to the measurement LED (D2) The negative pole of the reference LED (D1) is connected to the negative pole of the reference LED (D1), the positive pole of the measurement LED (D2) is connected to the fourth pin of the third integrated circuit (U3) through the fourth resistor (R4), and the positive pole of the reference LED (D1) is connected through the fifth The resistor (R5) is connected to the 6th pin of the third integrated circuit (U3), the 1st pin of the third integrated circuit (U3) is connected to the P1. Pin 2 is connected to pin 5 and then connected to VCC, and pin 3 of the third integrated circuit (U3) is grounded; the lock-in amplifier includes a photodiode (D3), a fourth integrated circuit (U4), and a fifth integrated circuit (U5). , the sixth integrated circuit (U6), the seventh integrated circuit (U7), the eighth integrated circuit (U8), ninth integrated circuit (U9), tenth integrated circuit (U10), eleventh integrated circuit (U11), sixth resistor (R6), seventh resistor (R7), eighth resistor (R8), Ninth resistor (R9), tenth resistor (R10), eleventh resistor (R11), twelfth resistor (R12), thirteenth resistor (R13), fourteenth resistor (R14), fifteenth resistor (R15), sixteenth resistor (R16), third capacitor (C3), fourth capacitor (C4), fifth capacitor (C5), sixth capacitor (C6), seventh capacitor (C7), eighth capacitor (C8), the ninth capacitor (C9) and the tenth capacitor (C10), the model of the photodiode (D3) is G8422-03, the fourth integrated circuit (U4), the fifth integrated circuit (U5), the sixth integrated circuit (U6), the seventh integrated circuit (U7), the eighth integrated circuit (U8), the ninth integrated circuit (U9), the tenth integrated circuit (U10), and the eleventh integrated circuit (U11) are LF356, AD829, AD829, AD829, AD829, OP177, CD4066 and CD4069, the sixth resistor (R6), the seventh resistor (R7), the eighth resistor (R8), the ninth resistor (R9), the tenth resistor (R10), the The resistance values of the eleventh resistor (R11), the twelfth resistor (R12), the thirteenth resistor (R13), the fourteenth resistor (R14), the fifteenth resistor (R15), and the sixteenth resistor (R16) are respectively 200KΩ, 2KΩ, 2KΩ, 2KΩ, 10KΩ, 2KΩ, 30KΩ, 2KΩ, 2KΩ, 2KΩ, 3KΩ, the third capacitor (C3), the fourth capacitor (C4), the fifth capacitor (C5), the sixth capacitor (C6) The capacitances of the seventh capacitor (C7), the eighth capacitor (C8), the ninth capacitor (C9), and the tenth capacitor (C10) are 0.01μF, 3300PF, 0.01μF, 1000PF, 0.01μF, 0.01μF, 0.01 μF, 1μF, 0.01μF, the anode and cathode of the photodiode (D3) are respectively connected to the second pin of the fourth integrated circuit (U4) and the ground wire, the third pin of the fourth integrated circuit (U4) is grounded, and the sixth resistor (R6) is connected between pin 2 and pin 6 of the fourth integrated circuit (U4), pin 3 of the fifth integrated circuit (U5) is grounded, the fourth capacitor (C4) and the eighth resistor (R8) It is connected in parallel between pin 2 and pin 6 of the fifth integrated circuit (U5), and the third capacitor (C3) is connected in series with the eighth resistor (R8) across the pin of the fourth integrated circuit (U4). Between pin 6 and pin 2 of the fifth integrated circuit (U5), pin 3 of the sixth integrated circuit (U6) is grounded, and the sixth capacitor (C6) is connected in parallel with the tenth resistor (R10) and connected across the sixth Between pin 2 and pin 6 of the integrated circuit (U6), the fifth capacitor (C5) and the ninth resistor (R9) are connected in series across the pin 6 of the fifth integrated circuit (U5) Between pin 2 of the sixth integrated circuit (U6), pin 3 of the seventh integrated circuit (U7) is grounded, and the twelfth resistor (R12) is connected across pin 2 of the seventh integrated circuit (U7) and Between pin 6, the seventh capacitor (C7) and the eleventh resistor (R11) are connected in series between pin 6 of the sixth integrated circuit (U6) and pin 2 of the seventh integrated circuit (U7). , the third pin of the eighth integrated circuit (U8) is grounded, the ninth capacitor (C9) and the fourteenth resistor (R14) are connected in parallel and connected between the second pin and the sixth pin of the eighth integrated circuit (U8) , the eighth capacitor (C8) and the thirteenth resistor (R13) are connected in series between the sixth pin of the seventh integrated circuit (U7) and the second pin of the eighth integrated circuit (U8), and the ninth integrated circuit The third pin of (U9) is grounded, the tenth capacitor (C10) is connected between the second pin of the ninth integrated circuit (U9) and the ground wire, the eleventh capacitor (C11) and the sixteenth resistor (R16) Connected in parallel between the 2nd pin and the 6th pin of the ninth integrated circuit (U9), the 12th pin and the 6th pin of the tenth integrated circuit (U10) are respectively connected with the 11th integrated circuit (U11) Pin 1 is connected to pin 2, pin 6 of the seventh integrated circuit (U7) and pin 6 of the eighth integrated circuit (U8) are respectively connected to pin 8 and pin 10 of the tenth integrated circuit (U10), The 9th pin of the tenth integrated circuit (U10) is connected to the 11th pin, and the fifteenth resistor (R15) is connected across the 2nd pin of the ninth integrated circuit (U9) and the 9th pin of the tenth integrated circuit (U10). Between, the fifth pin of the second integrated circuit (U2) is connected to the first pin of the eleventh integrated circuit (U11), and the sixth pin of the ninth integrated circuit (U9) is connected to the analog-to-digital converter (A/D) input connection.

Images