CN107576635B - Transparent liquid concentration measuring method and system based on reflection type optical fiber system - Google Patents
Transparent liquid concentration measuring method and system based on reflection type optical fiber system Download PDFInfo
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Abstract
The invention discloses a transparent liquid concentration measuring method and system based on a reflective optical fiber system, and relates to the field of liquid concentration measurement. The measuring method of the invention comprises the following steps: obtaining an optical signal; collecting transparent liquid transmission optical signals of a reflective optical fiber system; detecting an optical signal; amplifying and converting the photocurrent signal; and the data processing and displaying are used for fitting the data obtained by measuring a plurality of transparent liquids with known concentrations and different from each other into a formula, reading out the voltage signals of the transmitted light from the display module, and substituting the voltage signals into the formula obtained by fitting, so that the percentage of the solute content in the unknown transparent liquid is calculated. The invention is suitable for measuring the concentration of transparent liquid, and has the advantages of simple operation, quick measurement, high sensitivity, small system volume and easy carrying.
Description
Technical Field
The invention relates to the field of liquid concentration measurement, in particular to a transparent liquid concentration measurement method and system based on a reflection type optical fiber system.
Background
The liquid concentration is an important physical quantity reflecting the liquid characteristics, and the measurement and monitoring of the solution concentration has wide application in the fields of papermaking, chemical industry, sugar production, food, pharmacy, environmental monitoring and the like, and is an important technical means for ensuring the product quality and improving the product quality. The measurement of liquid concentration has therefore also been a hot spot of research by researchers. With the rapid development of industrialized society, environmental pollution problems are caused, so that people pay close attention to the sustainable development of the society, and environmental monitoring and protection problems are increasingly emphasized. The method has special significance and value for researching the liquid concentration measuring system and method because a large amount of chemical gas and liquid detection is needed in daily working environment of people, industrial process monitoring, medicine, national security and the like.
In the scientific research field, the research of liquid generally starts from the angles of refractive index, concentration, density, transmission absorption spectrum (luminescence characteristic), viscosity coefficient, surface tension, optical rotation and the like of the liquid, and establishes a relationship between the property of the liquid and other parameters for measuring the property of the liquid so as to analyze the essential property of the liquid. At present, chemical analysis, chromatography, infrared absorption spectrometry, optical refractive index, light intensity absorption and the like are mostly adopted for measuring the concentration of liquid at home and abroad. The analysis methods require huge volume and complex structure of the instruments, and cannot be applied to working conditions requiring real-time measurement.
Disclosure of Invention
The invention provides a transparent liquid concentration measuring method and a transparent liquid concentration measuring system based on a reflective optical fiber system, which have small system volume and compact structure, and the measuring method does not need a complicated calculation process, and can be suitable for working conditions which are convenient to carry and realize on-site real-time measurement.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the transparent liquid concentration measuring method based on the reflective optical fiber system comprises the following steps:
s1, a coupling lens is arranged between a light source and an input optical fiber, a light beam emitted by the light source is emitted into a coupling lens system, and the light beam enters the input optical fiber of a reflective optical fiber system after being emitted and focused and collimated by a self-focusing optical fiber;
s2, the light source emits the light beam through an outer layer optical fiber of the optical fiber probe composed of the input optical fibers, the light beam is emitted into the self-focusing optical fibers, the light beam is focused and collimated by the self-focusing optical fibers and then is emitted into transparent liquid, after the light beam emits out of the transparent liquid, the high reflection surface of the optical path regulator reflects the light beam, the light beam is led into the transparent liquid again, and after the light beam is focused and collimated by the self-focusing optical fibers, the light beam is output through an inner layer optical fiber of the optical fiber probe composed of the output optical fibers;
s3, the inner layer optical fiber of the optical fiber probe irradiates the light beam into a photodiode, and the photodiode collects and detects the light beam to obtain a photocurrent signal;
s4, the pre-amplifying circuit collects the photocurrent signals, amplifies and converts the photocurrent signals into voltage signals, the reference branch and the measuring branch collect the voltage signals to obtain reference signals and measuring signals, the second-stage differential amplifying circuit inputs the reference signals and the measuring signals and outputs amplified voltages, and the signal conversion module collects the amplified voltages and converts the amplified voltages into digital signals;
s5, repeating the steps S1-S4, measuring transparent solutions with the same solutes and different concentrations in the specified quantity under the same optical path to obtain corresponding digital signals, and establishing a regression equation according to the concentrations and the corresponding digital signals;
s6, detecting the transparent liquid to be detected, obtaining a digital signal of the transparent liquid to be detected, solving the regression equation according to the digital signal of the transparent liquid to be detected, and recording the obtained equation solution as the concentration of the transparent liquid to be detected.
Further, the light source adopts an LED light source, and the wavelength of the LED light source is consistent with the solute light absorption wavelength of the transparent liquid.
Further, the coupling lens system comprises a single lens and a telescope group, wherein the light beam is refracted by the single lens, then is parallelly incident to an eyepiece unit of the telescope group, and then is emitted through an objective lens unit of the telescope group.
Further, the reference branch includes: a silicon photodiode and photodiode pre-amplifier circuit sealing the mirror window; the measurement branch comprises: a silicon photodiode and the photodiode pre-amplifier circuit sealing the mirror window; the reference signal and the measurement signal are synchronously controlled by a signal processing module.
Further, the specified number is not less than nine.
The invention also provides a transparent liquid concentration measurement system based on the reflection type optical fiber system, which comprises: the optical sensor comprises an optical signal source module, an optical coupling module, a reflective optical fiber system module, a photoelectric detection module, a micro-current amplifying module, an analog-to-digital conversion module, a microcontroller module, a keyboard input module and a registering display module, wherein the optical signal source module is connected with the reflective optical fiber system module through the optical coupling module, the reflective optical fiber system module is connected with the photoelectric detection module, the photoelectric detection module is connected with the micro-current amplifying module, the micro-current amplifying module is connected with the microcontroller module through the A/D conversion module, and the microcontroller module is also connected with the keyboard input module and the registering display module.
Further, the reflective optical fiber system module includes: the optical fiber comprises an input optical fiber, an optical fiber probe, a self-focusing optical fiber, an optical path regulator and an output optical fiber.
Furthermore, the self-focusing optical fiber is bonded with the input optical fiber to form a light beam input end, the self-focusing optical fiber is bonded with the output optical fiber to form a light beam output end, the input optical fiber forms an outer optical fiber of the optical fiber probe, the output optical fiber forms an inner optical fiber of the optical fiber probe, and after the outer optical fiber of the optical fiber probe and the inner optical fiber of the optical fiber probe are bonded with the self-focusing optical fiber, the functions of collimating, parallel emergent and focusing incidence of the light beam can be realized.
Further, the optical path regulator of the high reflection surface comprises an opaque cylindrical shell, an optical fiber probe, an optical path regulator and a high reflection surface, wherein the opaque cylindrical shell is made of hard corrosion-resistant materials, the optical fiber probe is arranged outside the opaque cylindrical shell, the optical path can be regulated by sliding the optical fiber probe, a small round hole sealing cover is arranged at the end part of the opaque cylindrical shell, a hollow support frame is arranged at the small round hole sealing cover and used for supporting the high reflection surface, a light beam is arranged in the optical path regulator, and incidence and reflection are carried out between the optical fiber probe and the high reflection surface.
The beneficial effects of the invention are as follows: the measuring system has compact structure and small volume, is convenient to carry, does not need complicated calculation process, can measure results in real time, and can adapt to the working condition that the measuring system needs to be carried with and can obtain the measuring results on site.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a transparent liquid concentration measurement system based on fiber optic sensing technology;
FIG. 2 is a schematic diagram of a reflective optical fiber system of a transparent liquid concentration measurement system based on fiber optic sensing technology;
FIG. 3 is a schematic light-guiding diagram of a reflective optical fiber system of a transparent liquid concentration measurement system based on optical fiber sensing technology;
fig. 4 is a circuit diagram of the two-stage differential amplification circuit;
FIG. 5 is a hardware circuit diagram of the signal processing module;
fig. 6 is a graph of regression equation data fitting in a transparent liquid concentration measurement method based on an optical fiber sensing technology.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments for better understanding of the technical solution of the present invention by those skilled in the art.
The transparent liquid concentration measuring method based on the reflective optical fiber system comprises the following steps:
s1, a coupling lens is arranged between an LED light source and an input optical fiber, the coupling lens system comprises a single lens and a telescope group, light beams are refracted by the single lens and then parallelly enter an eyepiece unit of the telescope group, then are emitted by an objective unit of the telescope group, the light beams enter the input optical fiber of a reflective optical fiber system after being emitted and focused by a self-focusing optical fiber, and the output power of the LED light source is 0.3w;
s2, the light source emits the light beam into the self-focusing optical fiber through an outer layer optical fiber of the optical fiber probe composed of the input optical fibers, the light beam is focused and collimated by the self-focusing optical fiber and then is emitted into transparent liquid, after the light beam emits the transparent liquid, the high reflection surface of the optical path regulator reflects the light beam, the light beam is LED into the transparent liquid again, after the light beam is focused and collimated by the self-focusing optical fiber, the light beam is output by an inner layer optical fiber of the optical fiber probe composed of the output optical fiber, wherein the wavelength of the LED light source is consistent with the solute light absorption wavelength of the transparent liquid;
s3, the inner layer optical fiber of the optical fiber probe irradiates the light beam into a photodiode, and the photodiode collects and detects the light beam to obtain a photocurrent signal;
s4, the pre-amplifying circuit collects the photocurrent signals, amplifies and converts the photocurrent signals into voltage signals, the reference branch and the measuring branch collect the voltage signals to obtain reference signals and measuring signals, the second-stage differential amplifying circuit inputs the reference signals and the measuring signals and outputs amplified voltages, and the signal conversion module collects the amplified voltages and converts the amplified voltages into digital signals;
s5, repeating the steps S1-S4, and measuring 9 transparent solutions of carmine samples under the same optical path to obtain corresponding digital signals, and establishing a regression equation according to the concentration and the corresponding digital signals, wherein a measurement example data table is shown in Table 1:
table 1 measurement example data table
| Carmine sample concentration (mg/L) | Output voltage (V) |
| 20 | 0.67 |
| 18 | 0.75 |
| 16 | 0.85 |
| 14 | 0.96 |
| 12 | 1.09 |
| 10 | 1.23 |
| 8 | 1.40 |
| 6 | 1.59 |
| 4 | 1.81 |
Regression equation is y= 36.7233-29.689x+6.46138x 2 The fitted curve is shown in fig. 6;
s6, detecting the carmine transparent liquid to be detected, obtaining a digital signal of the transparent liquid to be detected, solving the regression equation according to the digital signal of the transparent liquid to be detected, and recording the obtained equation solution as the concentration of the carmine transparent liquid to be detected.
The invention also provides a transparent liquid concentration measurement system based on the reflection type optical fiber system, which comprises: the device comprises an optical signal source module 101, an optical coupling module 102, a reflective optical fiber system module 103, a photoelectric detection module 104, a micro-current amplification module 105, an A/D conversion module 106, a microcontroller module 107, a keyboard input module 108 and a register display module 109. The light source module 101 is connected with the reflective optical fiber system module 103 through the optical coupler module 102, the reflective optical fiber system module 103 is connected with the photoelectric detection module 104, the photoelectric detection module 104 is connected with the micro-current amplification module 105, the micro-current amplification module 105 is connected with the microcontroller module 107 through the A/D conversion module 106, and the microcontroller module 107 is also connected with the keyboard input module 108 and the register display module 109.
The optical signal source module 101 is used for initial signal emission of the system, the signal emitted by the optical signal source module 101 is key to the system, and has high requirement on stability, however, the LED light has the characteristics of wide wavelength distribution, low price, small volume, high brightness, environmental protection, firmness, durability and the like, and can meet the requirement of the invention, so that the LED light source is selected as the signal source of the system.
An optical coupling module 102, for coupling the initial optical signal emitted by the optical signal source module 101 into the reflective optical fiber system module 103, in the present invention, a lens system matched between the input end surfaces of the signal source module 101 and the reflective optical fiber system module 103 is disposed to achieve efficient coupling, where the lens system includes a single lens and a telescope lens group.
The light beam of a certain wavelength emitted from the light source module 101 is converged by a single lens having a diameter of 20mm and a focal length of 30mm, and then is incident on a window of the telescope unit, and is then magnified by a magnification of 40 times by a combination of the eyepiece unit and the objective lens unit lens. When the optical signal source module 101 and the reflective optical fiber system module 103 are optimally coupled, the eyepiece is used as an input end of a light beam, the objective lens is used as an output end of the light beam, 40 times of light spots can be reduced, and the reflective optical fiber system input end 206 is adjusted to the central position of the output focus of the telescope barrel.
The reflective optical fiber system module 103 plays a role in light guiding in the system, the reflective optical fiber system module 103 consists of a light path regulator 206 with a high reflection surface, a self-focusing optical fiber 205 and a multimode optical fiber, the separation of incident light and reflected light can be realized by utilizing the reflective optical fiber system module 103, the light path of a light beam in transparent liquid to be detected can be regulated, and the design of an effective light-proof shell is realized, and the structure of the reflective optical fiber system module 103 is shown in figure 2.
A reflective optical fiber system 103 comprising: an input optical fiber 201, an output optical fiber 202, an optical fiber probe 203, a self-focusing optical fiber 204 (the diameter of the self-focusing optical fiber is 2.1 mm), a self-focusing optical fiber 205 (the diameter of the self-focusing optical fiber is 3 mm), an optical path regulator 206, a high reflection surface 211 (the thickness is 3mm of a silver mirror), a hollowed-out bracket 212 and a fixing screw 213. The input optical fiber 201 and the output optical fiber 202 are respectively bonded with the self-focusing optical fiber 204 to form an input end face 207 and an output end face 208, so that efficient coupling of optical signals is realized. The fiber optic probe 203 comprises two sections, an inner fiber 209 (quartz fiber, numerical aperture 0.37) and an outer fiber 210 (quartz fiber, numerical aperture 0.22). The light beam is transmitted to the end face 210 of the optical fiber probe 203 by the input end face 207, vertically enters the end face of the self-focusing optical fiber 205, is focused and collimated by the self-focusing optical fiber 205, vertically enters the high reflection surface 211 in the optical path regulator 206, receives the light beam reflected by the reflection surface 211 again by the end face of the self-focusing optical fiber 205, and is coupled to the inner layer optical fiber 209 of the optical fiber probe 203 for output after focusing. The optical path diagram is shown in fig. 3 for an input beam 301 and an output beam 302.
The light beam propagates forward in the self-focusing optical fiber 205 through repeated repetition of divergent focusing, and when the self-focusing optical fiber 205 length is taken from a quarter or an odd multiple of a quarter of the period length of the self-focusing optical fiber 205, the light beam is emitted along the tangent of the sinusoidal curve in an opposite direction and parallel to the optical fiber axis, thereby achieving self-focusing collimation.
The light beam 302 entering the inner layer fiber 209 of the fiber probe 203 is the light beam 302 after the transparent liquid sample to be measured is reflected by the reflecting surface, so that the information of the transparent liquid sample is necessarily carried. Since the intensity of the light beam 302 is closely related to the concentration of the transparent liquid sample to be measured, i.e. the solute content in the sample, the percentage of the solute content of the transparent liquid sample to be measured can be obtained from the intensity of the light beam 302 emitted from the output end 208, which is the measurement principle of the system.
The key to measuring the transparent liquid sample by the present system is to measure the intensity of the light beam exiting from the output face 208. Therefore, ensuring its stability is critical to obtaining accurate measurements.
Factors that affect the intensity stability of the beam exiting output 208 include:
first, the stability of the initial light intensity entering the fiber from the input 201, i.e., the stability of the output of the optical signal source module 101. The optical signal source of the system is an LED light source, and the output voltage is stable after measurement, so that the system meets the measurement requirement;
secondly, the factors influencing the intensity of the light signal emitted from the output end face 208 are not only the concentration of the transparent liquid sample, but also whether the parallel light beam emitted from the optical fiber probe 203 can vertically enter the high reflection surface 211;
therefore, only if the parallel light beam emitted from the fiber probe 203 is always perpendicular to the high reflection surface 211, the intensity of the light beam emitted from the output end surface 208 can be ensured to be only related to the concentration of the transparent liquid sample.
In the specific measurement, the initial light beam emitted from the outer layer optical fiber 210 on the end surface of the optical fiber probe 203 is reflected by the high reflection surface 211 after passing through the transparent liquid to be measured, passes through the transparent liquid again, and finally enters the output end surface 208 from the inner layer optical fiber 209 through the output optical fiber 202. Therefore, to ensure that the light beam reflected by the reflecting surface is efficiently coupled into the inner layer fiber 209, it is necessary to ensure that the outgoing light beam from the fiber probe 203 remains perpendicular to the highly reflecting surface 211. The optical fiber probe 203 and the self-focusing optical fiber 205 which are bonded together are embedded in the optical path regulator 206 and can move, so that the optical fiber probe 203 and the high reflection surface 211 are always kept vertical in the later measurement, the reflection light beam is always vertical to the end surface of the self-focusing optical fiber 205, the distance between the optical fiber probe 203 and the high reflection surface 211 can be regulated, namely the physical optical path of the transmission light beam in a transparent liquid sample can be regulated, and the measurement range is widened.
The light beam emitted from the outer layer optical fiber 210 on the end surface of the optical fiber probe 203 is incident on the high reflection surface 211 through the transparent liquid sample, is reflected by the high reflection surface 211, and is emitted from the inner layer optical fiber 209 on the end surface of the optical fiber probe 203 through the transparent liquid sample again. Since the probe is exposed, there must be ambient light that also enters the fiber along with the reflected light. The ambient light does not carry any information about the sample. Therefore, ambient light must be filtered out.
To filter out the ambient light described above, the present invention provides an optical path length adjuster 206 as shown in FIG. 2. The optical path regulator 206 can be made of any hard corrosion-resistant material, is formed by encircling the optical path regulator into a cylinder shape, has a bottom surface with a diameter slightly larger than that of the optical fiber probe 203, can be externally arranged on the optical fiber probe 203, and ensures that the optical fiber probe slides on the optical fiber probe 203; a small round hole is formed at the end part of the optical path regulator 206, a transparent liquid sample to be measured enters the small round hole, a hollow support frame 212 for supporting a high reflection surface 211 is arranged above the small round hole, the diameter of the reflection surface is far greater than that of the small round hole and smaller than that of the optical path regulator 206, and the design can filter ambient light, so that the measurement is facilitated; meanwhile, a scale is carved on the material for fixing the optical fiber probe, so that the moving distance of the optical path regulator 206, namely the physical optical path of the light beam in the transparent liquid sample, can be observed, and the fixing is realized by the fixing screw 213 in the measuring process.
The photo detection module 104 is configured to convert the optical signal collected from the transparent solution into an electrical signal, specifically, a photodiode. The light beam 302 emitted from the output optical fiber 201 of the reflective optical fiber system module 103 is focused and collimated by the self-focusing optical fiber 205, and then enters the surface of a photodiode, and the photodiode converts the optical signal into an electrical signal. The photodiode and the self-focusing optical fiber 205 are bonded together and sealed in a cassette to avoid the influence of external light. The light intensities are different, so that the light intensities are also different, and the light intensities are in direct proportion.
The micro-current amplifying module 105 is used for amplifying the photocurrent signal and converting the photocurrent signal into a voltage signal, and the high-gain ICL7650 operational amplifier is adopted to realize the amplification and conversion of the weak photocurrent signal. ICL7650 is a chopper stabilized high-precision operational amplifier integrated by adopting a CMOS process, and can meet the requirements of operational amplifiers that input impedance is far larger than feedback resistance, bias current is smaller than measured current, offset voltage and drift are small, gain and common mode rejection ratio is high, noise is small, and the like. The micro-electro-optic flow secondary amplifying circuit based on ICL7650 is shown in figure 4, and consists of a photodiode pre-amplifying measurement branch, a photodiode pre-amplifying reference branch and a secondary amplifying circuit. R1 is ICL7650 input current limiting protection resistor, C1 and R2 form a feedback compensation network, bandwidth is reduced, self-oscillation generated by phase shift of R2, R3, R4 and C2 is prevented, and R3 and C2 are used for filtering chopper peak noise of ICL 7650; the smaller resistors R2, R3 and R4 form a T-type network structure to generate high-resistance feedback, so as to improve the stability and precision of the gain and reduce noise, and the output voltage u1= -IS (r2+r4+r2×r4/R3).
The reference branch is routed with a silicon photodiode and a photodiode pre-amplifying circuit which seal a plane mirror window, and the output voltage is U2. The reference branch and the measurement branch are completely of symmetrical design, and the two branches are subjected to differential amplification in the secondary amplifying circuit, so that the influence of external factors on component parameter drift can be eliminated, and the output voltage Uout= (1+R3/R1) R4×U1/(R3+R3) -R4×U2/R3 of the secondary amplifying circuit. ICL7650 operational amplifier is adopted in the secondary amplification module, the amplification factor is 2, the feedback resistance value is changed, the amplification factor can be changed, the secondary amplification only plays an auxiliary amplification role in practice, the key is to reduce the influence of external environment on system measurement, and the actual amplification of the whole system circuit is mainly completed by the photo-current signal pre-amplification module.
The a/D conversion module 106 is configured to convert the output analog voltage signal into a digital signal. MC14433 is selected as the A/D converter 106 in the signal conversion module, which is a three-bit half-double integration A/D converter introduced by Motorola corporation of America, wherein all CMOS analog circuits and digital circuits are integrated, and the signal conversion module has the characteristics of strong interference resistance, high input impedance (1000 MΩ), high conversion speed (1-10 times/second) and the like. The analog input of MC14433 is input by pin VX, the input range is 199.9mV and 1.999V, the corresponding input reference voltage is input by VR pin, and the reference voltage is 200mV and 2V respectively. And selecting a proper measuring range according to a voltage range corresponding to the absorption light intensity of the transparent solution to be measured. The reference voltage of MC14433 is provided by integrated voltage regulator chip MC 1403. The output voltage of the MC1403 is divided by a variable resistor, and the divided voltage is connected to the a/D converter reference power supply terminal VR. MC14433 is selected as an A/D converter, and a word bit dynamic scanning BCD code output mode is adopted, namely, thousands, hundreds, tens and units BCD codes are alternately output at Q0-Q3 in a time sharing mode, and synchronous word bit strobe pulses are output at DS1-DS4 ends to obtain A/D conversion data.
The micro-controller module 107 is used for processing the output data of the a/D converter 106, and is a core part of the whole measurement system body, and is divided into a hardware part and a data processing flow part. As shown in fig. 5, the data processor 501 in the hardware part uses a general purpose processor AT89C52 in the 8051 series, which contains 8 kbytes of read-only program memory (PEROM) and 256 bytes of random read data memory (RAM). The output port of the multi-path gating pulse of MC14433 is connected with the pin of the data output end of the BCD code and the P1 of the singlechip. When the data conversion of MC14433 is finished, related pins DU and EOC are short-circuited, and are connected with an external interrupt interface INT1 of the singlechip, and a query or interrupt method is adopted to realize the data reading of the digital-to-analog converter by the processor.
The register display module 109 adopts serial static display, and realizes four-bit LED display by utilizing two I/O interfaces of a singlechip and four 74LS164 shift registers. The four shift registers are connected end to end, when the first 8 clock pulses arrive, data enter the first 74LS164 shift register from the serial input port RXD of the singlechip, when the second 8 clock pulses arrive, the data in the first shift register are shifted into the second chip, and new data enter the first shift register from the RXD end; when the fourth 8 clock pulses arrive, the data display is completed, the first sent data appears in the rightmost shift register, and the last sent data appears in the leftmost shift register, so that the data display is completed.
The whole flow of the measuring method comprises the steps of calibrating a large amount of transparent liquid samples, determining a model equation, loading the model equation into a microprocessor, starting measurement, performing data reading, digital filtering, data processing and the like through an A/D conversion module 106, and finally displaying a measuring result on a nixie tube to finish the measurement.
Since the reading on the data registering display module 109 reflects the concentration of the transparent liquid sample, calibration is necessary to obtain a specific value of the transparent liquid concentration from this voltage reading. The specific method is to arrange a plurality of transparent liquid samples with known concentration and different concentrations, respectively put the transparent liquid samples into the system, and sequentially read out and record the voltages. The resulting data is fit by software to a formula, which is as follows:
y=A0+A1x+A2x 2
the formula is a function of y with respect to x, x represents the measured voltage value, y represents the concentration of the transparent liquid sample, and A0, A1 and A2 are coefficients to be measured. From the scaling data that have been obtained, the values of these three coefficients can be obtained. In the subsequent measurement, the measurement conditions (mainly the input light intensity of the signal source module 101 and the physical optical path length from the optical fiber probe 203 to the high reflection surface 211) are kept unchanged, a transparent liquid sample with unknown concentration is put into the system, the voltage value is read out from the display module 109, and the solution of the formula is solved according to the voltage value, wherein the solution of the formula is recorded as the concentration of the unknown transparent liquid sample.
The beneficial effects of the invention include:
1. the measuring method does not need to rely on huge high-volume large-scale equipment, the measuring system has compact structure and relatively low price, and is convenient to maintain, so that the measuring cost is reduced, and the portable measuring system is convenient to carry about and popularize and use;
2. the operation of the measuring method is easy to be carried out, the measuring time is short, and the real-time performance of the measurement can be realized;
3. the measuring system can adopt different LED light sources and photodiodes according to different solute absorption wavelengths, can adapt to wide measuring solute types, and has the advantages of strong pertinence, high sensitivity and good measuring accuracy;
4. the optical path entering the measuring liquid can be adjusted, so that the accurate measurement of different solution concentrations can be realized, and the measuring range is expanded;
5. the measuring device is light and small, is easy to carry, is intelligent, is not interfered by external environment, can perform on-site real-time measurement, is easy to operate and convenient to clean and maintain;
6. the LED light source, the multimode optical fiber, the photodiode and the like have reliable working performance and low cost.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present invention should be included in the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.
Claims (7)
1. The transparent liquid concentration measuring method based on the reflection type optical fiber system is characterized by comprising the following steps of:
s1, a light source emits a light beam to be injected into a coupling lens system, and the light beam enters an input optical fiber of a reflective optical fiber system after being focused and collimated by a self-focusing optical fiber;
s2, the light source emits the light beam into the self-focusing optical fiber through an outer layer optical fiber of the optical fiber probe composed of the input optical fibers, the light beam is focused and collimated by the self-focusing optical fiber and then is emitted into transparent liquid, after the light beam emits the transparent liquid, the light beam is reflected by a high reflection surface of a high reflection surface light path regulator, the light beam is led into the transparent liquid again, and after the light beam is focused and collimated by the self-focusing optical fiber, the light beam is output by an inner layer optical fiber of the optical fiber probe composed of the output optical fiber;
the optical path regulator of the high reflection surface comprises an opaque cylindrical shell, an optical fiber probe, an optical path regulator and a high reflection surface, wherein the optical fiber probe is arranged outside the opaque cylindrical shell, the optical path can be regulated by sliding the optical fiber probe, a small round hole sealing cover is arranged at the end part of the opaque cylindrical shell, a hollow support frame is arranged at the small round hole sealing cover and is used for supporting the high reflection surface, and light beams are incident and reflected between the optical fiber probe and the high reflection surface in the optical path regulator; the diameter of the high reflection surface is far larger than that of the small round hole and smaller than that of the opaque cylindrical shell of the optical path regulator;
s3, the inner layer optical fiber of the optical fiber probe irradiates the light beam into a photodiode, and the photodiode collects and detects the light beam to obtain a photocurrent signal;
s4, the pre-amplifying circuit collects the photocurrent signals, amplifies and converts the photocurrent signals into voltage signals, the reference branch and the measuring branch collect the voltage signals to obtain reference signals and measuring signals, the second-stage differential amplifying circuit inputs the reference signals and the measuring signals and outputs amplified voltages, and the signal conversion module collects the amplified voltages and converts the amplified voltages into digital signals;
s5, repeating the steps S1-S4, measuring transparent solutions with the same solutes and different concentrations in the specified quantity under the same optical path to obtain corresponding digital signals, and establishing a regression equation according to the concentrations and the corresponding digital signals;
s6, detecting the transparent liquid to be detected, obtaining a digital signal of the transparent liquid to be detected, solving the regression equation according to the digital signal of the transparent liquid to be detected, and recording the obtained equation solution as the concentration of the transparent liquid to be detected.
2. The method for measuring the concentration of a transparent liquid based on a reflective optical fiber system according to claim 1, wherein the light source is an LED light source, and the wavelength of the LED light source is consistent with the solute light absorption wavelength of the transparent liquid.
3. The method for measuring the concentration of the transparent liquid based on the reflective optical fiber system according to claim 1, wherein the coupling lens system comprises a single lens and a telescope group, and the light beam is refracted by the single lens, then is parallel incident to an eyepiece unit of the telescope group, and then is emitted through an objective unit of the telescope group.
4. The method of claim 1, wherein the reference arm comprises: a silicon photodiode and photodiode pre-amplifier circuit sealing the mirror window; the measurement branch comprises: a silicon photodiode and the photodiode pre-amplifier circuit sealing the mirror window; the reference signal and the measurement signal are synchronously controlled by a signal processing module.
5. The transparent liquid concentration measurement method based on a reflection type optical fiber system according to claim 1, wherein the specified number is not less than nine.
6. Transparent liquid concentration measurement system based on reflection type optical fiber system, characterized by comprising: the device comprises an optical signal source module, an optical coupling module, a reflective optical fiber system module, a photoelectric detection module, a micro-current amplification module, an A/D conversion module, a microcontroller module, a keyboard input module and a register display module, wherein the optical signal source module is connected with the reflective optical fiber system module through the optical coupling module, the reflective optical fiber system module is connected with the photoelectric detection module, the photoelectric detection module is connected with the micro-current amplification module, the micro-current amplification module is connected with the microcontroller module through the A/D conversion module, and the microcontroller module is also connected with the keyboard input module and the register display module;
the reflective fiber optic system module comprises: the optical fiber probe comprises an input optical fiber, an optical fiber probe, a self-focusing optical fiber, a high reflection surface light path regulator and an output optical fiber;
the optical path regulator of the high reflection surface comprises an opaque cylindrical shell, an optical fiber probe, an optical path regulator and a high reflection surface, wherein the optical fiber probe is arranged outside the opaque cylindrical shell, the optical path can be regulated by sliding the optical fiber probe, a small round hole sealing cover is arranged at the end part of the opaque cylindrical shell, a hollow support frame is arranged at the small round hole sealing cover and is used for supporting the high reflection surface, and light beams are incident and reflected between the optical fiber probe and the high reflection surface in the optical path regulator; the diameter of the high reflection surface is far larger than that of the small round hole and smaller than that of the opaque cylindrical shell of the optical path regulator.
7. The transparent liquid concentration measurement system based on a reflection type optical fiber system according to claim 6, wherein the self-focusing optical fiber and the input optical fiber are bonded to form a light beam input end, the self-focusing optical fiber and the output optical fiber are bonded to form a light beam output end, the input optical fiber forms an outer optical fiber of the optical fiber probe, the output optical fiber forms an inner optical fiber of the optical fiber probe, and the outer optical fiber of the optical fiber probe and the inner optical fiber of the optical fiber probe are bonded to the self-focusing optical fiber, so that the functions of collimating, parallel outgoing and focusing incidence of the light beam can be realized.
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| CN109490212A (en) * | 2018-12-11 | 2019-03-19 | 南京航空航天大学 | A kind of measuring system and measurement method of the typical fruit surface wax content based on multichannel optical fiber system |
| CN109507144B (en) * | 2018-12-24 | 2021-11-26 | 中国科学院合肥物质科学研究院 | Embedded water organic phosphorus pesticide residue detection device and method |
| CN112577927A (en) * | 2020-11-24 | 2021-03-30 | 南京航空航天大学 | Beverage pigment concentration measuring system |
| CN112964658A (en) * | 2021-04-13 | 2021-06-15 | 彦旭科技(武汉)有限公司 | Liquid concentration measuring method and device based on illumination attenuation |
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