CN113433092B - Calibration method, calibration device and calibration system for laser gas analysis system - Google Patents
Calibration method, calibration device and calibration system for laser gas analysis system Download PDFInfo
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- CN113433092B CN113433092B CN202110698740.7A CN202110698740A CN113433092B CN 113433092 B CN113433092 B CN 113433092B CN 202110698740 A CN202110698740 A CN 202110698740A CN 113433092 B CN113433092 B CN 113433092B
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
Abstract
The application discloses a calibration method, a calibration device and a calibration system of a laser gas analysis system, wherein the nonlinear representation of the laser scanning wavelength of a reference system is obtained based on etalon measurement parameters and output data; obtaining laser parameters of a target system determined based on the absorption spectrum line range of a detected gas in background gas, and obtaining the nonlinear representation of the laser scanning wavelength of the target system; and obtaining the incidence relation between the peak value of the absorption peak output by the target system and the recording parameter of the reference system in the standard gas introducing process based on the difference between the nonlinear characterization of the target system and the nonlinear characterization of the reference system, and obtaining the calibration coefficient for calculating the concentration of the measured gas of the target system. The application reduces the use frequency of the standard gas in the process of calibrating the batch measurement system, can effectively solve the problems of pollution caused by the standard gas, difficulty in storage, difficulty in transportation and the like, and can improve the efficiency of calibrating the batch target system.
Description
Technical Field
The invention relates to the technical field of laser measurement, in particular to a calibration method, a calibration device and a calibration system of a laser gas analysis system.
Background
The gas concentration detection is widely applied in the field of industrial production, a tunable laser is adopted as a light source in a laser gas analysis system, and direct absorption signals of gas molecules are obtained by scanning the laser scanning wavelength, but because the laser and an electronic component are different, the linearity of the output scanning wavelength is inconsistent, and the obtained direct absorption signals are different, so that each instrument needs to calibrate the system by using a standard gas (the gas to be detected with known concentration) to ensure the accuracy of the system measurement.
When the standard gas method is adopted for calibration at present, a series of problems can occur, for example, potential safety hazards exist, some detected gases are toxic, flammable and explosive, the danger in the production environment can be increased due to frequent operation of the gases in the batch production process, meanwhile, the calibration scanning time is long, for example, high-temperature gas calibration needs to provide a stable constant-temperature environment, the scanning time in the process of heating equipment to the target temperature is long, and because the standard gas is a consumable product, the method for calibrating the standard gas is high in cost and needs to be continuously purchased, particularly, some special gases with high acquisition difficulty are obtained, the production and transportation cost of a manufacturer is also high, the tail gas treatment difficulty is high, and a large amount of toxic and harmful gases can be discharged only through professional equipment and step treatment.
For the related technologies, the inventor thinks that there are a series of defects such as potential safety hazard, high cost, long time consumption, and complicated exhaust emission treatment when the standard gas is used to calibrate the accuracy of the system, so it is necessary to reduce the frequency of using the standard gas when calibrating the batch measurement system to overcome the above defects.
Disclosure of Invention
In the process of calibrating a batch measurement system, in order to reduce the use frequency of standard gas, reduce potential safety hazard and cost caused by the standard gas and improve calibration efficiency, the application provides a calibration method, a calibration device and a calibration system for a laser gas analysis system.
In a first aspect, the present application provides a calibration method for a laser gas analysis system, which adopts the following technical scheme:
a calibration method for a laser gas analysis system, which calibrates a target system with lasers of the same type through a reference system calibrated by a calibration gas, comprises the following steps:
obtaining a nonlinear characterization of a laser scanning wavelength of a reference system based on the etalon measurement parameters and the output data;
acquiring laser parameters of a target system determined based on the absorption spectral line range of a detected gas in background gas;
obtaining a nonlinear representation of the laser scanning wavelength of the target system based on the etalon measurement parameters and the output data;
obtaining an incidence relation between a peak value of an absorption peak output by the target system and a recording parameter in the standard gas introducing process of the reference system based on the difference between the nonlinear representation of the target system and the nonlinear representation of the reference system;
and acquiring a calibration coefficient calculated by the concentration of the measured gas of the target system based on the incidence relation of the recording parameters of the peak value of the absorption peak output by the target system in the calibration process of the reference system and the calibration coefficient calculated by the reference system for the concentration of the measured gas.
Because the gas measurement system needs to be calibrated in the prior technical means, the method has some efficiency problems and difficulties, and by adopting the technical scheme, a calibrated reference system is adopted to calibrate other target systems; firstly, an etalon is placed between a transmitting module and a receiving module of a calibrated reference system, and because the etalon has fixed physical parameters, when laser emitted by a laser passes through the etalon, the receiving module receives a direct absorption signal after the etalon absorbs part of light, and the nonlinear representation of the laser scanning wavelength of the reference system can be obtained according to the known laser parameters of the reference system; acquiring an absorption spectral line range of a gas to be measured in a background gas (such as air, carbon dioxide and other harmless gases) environment, determining laser parameters of a target system, then placing an etalon between a transmitting module and a receiving module in the target system, and acquiring nonlinear representation of laser scanning wavelength of the target system based on the measurement parameters and output data of the etalon; and then, according to the difference between the nonlinear characterization of the target system and the nonlinear characterization of the reference system, obtaining the incidence relation between the peak value of the absorption peak output by the target system and the recording parameter in the process of introducing standard gas into the reference system, and by using the known parameter of the reference system (because the calibration coefficient for calculating the concentration of the measured gas after introducing standard gas into the reference system is known and is a way of frequently calibrating the concentration of the measured gas at present), obtaining the calibration coefficient for calculating the concentration of the measured gas of the target system, and calibrating other target systems of the same model by using the mode and the etalon as a conversion standard without calibrating the introduction of standard gas into each target system to be calibrated.
In target systems to be calibrated of the same model, only one of the target systems to be calibrated needs to be extracted for calibration of the standard gas, and the target systems can be used as reference systems for calibrating the other target systems, so that the use frequency of the standard gas is greatly reduced, and the potential safety hazard caused by the standard gas calibration mode is further reduced; the standard gas used for calibration is a disposable consumable, and the standard gas in the scheme can be repeatedly used for many times, so that the scheme also greatly reduces the purchase cost of the standard gas compared with the related technology; in addition, the scheme greatly reduces the use frequency of the standard gas, thereby greatly reducing the links and the flow of tail gas treatment and having the effect of improving the calibration efficiency of the batch measurement system.
Optionally, the step of obtaining a non-linear characterization of the laser scanning wavelength of the reference system includes:
acquiring a direct absorption signal generated by an etalon based on the etalon arranged between a transmitting module and a receiving module of a reference system, and acquiring a nonlinear representation of a laser scanning wavelength of the reference system based on the direct absorption signal and a scanning wavelength interval between two adjacent wave peaks determined by the physical characteristics of the etalon;
acquiring a curve relation between a gas direct absorption signal of the reference system and the scanning wavelength of the laser based on the nonlinear representation of the scanning wavelength of the laser of the reference system and the gas direct absorption signal corresponding to the standard gas of the reference system;
the step of determining laser parameters of the target system comprises:
adjusting a laser of a target system by using an absorption spectrum line of background gas or a wavelength meter and taking the wavelength position of an absorption peak of the gas to be detected as a reference to obtain laser parameters of the target system, wherein the laser parameters comprise a scanning current minimum reference value, a scanning current maximum reference value and a laser temperature;
the step of obtaining a non-linear characterization of the laser scanning wavelength of the target system comprises:
acquiring a direct absorption signal generated by an etalon based on the etalon arranged between a transmitting module and a receiving module of a target system, and acquiring a nonlinear representation of a laser scanning wavelength of the target system based on the direct absorption signal and a scanning wavelength interval between two adjacent wave peaks determined by the physical characteristics of the etalon;
the step of obtaining the incidence relation between the peak value of the absorption peak output by the target system and the recording parameter in the process of introducing the standard gas into the reference system comprises the following steps:
acquiring curve relations between a gas direct absorption signal and scanning time of a target system and between the gas direct absorption signal and the scanning wavelength based on the nonlinear characterization of the laser scanning wavelength of the reference system and the nonlinear characterization of the laser scanning wavelength of the target system;
obtaining the peak value of a gas direct absorption signal corresponding to the introduced standard gas in the target system based on the curve relation between the gas direct absorption signal of the target system and the scanning time;
the step of obtaining calibration coefficients for the target system's measured gas concentration calculation includes:
and acquiring the calibration coefficient calculated by the concentration of the measured gas of the target system based on the peak value of the direct gas absorption signal of the target system, the calibration coefficient calculated by the concentration of the measured gas of the reference system and the peak value of the direct gas absorption signal corresponding to the introduced standard gas in the reference system.
By adopting the technical scheme, when the target system is calibrated, the etalon is used as a measuring standard to perform conversion between the reference system and the target system, and the etalon is used for acquiring the nonlinear representation of the laser scanning wavelength of the reference system because the laser parameters of the reference system are known; then, the target system is operated, the position of the absorption line of the gas to be measured can be obtained by means of the absorption line of the background gas in the surrounding environment of the target system or by means of a wavelength meter, then the laser parameter of the target system is adjusted by taking the position of the absorption line of the gas to be measured as a reference, the output laser wavelength range of the laser is enabled to be matched with the absorption line of the gas to be measured, wherein the mode of obtaining the position of the absorption line of the gas to be measured by using the background gas in the surrounding environment of the target system is that the position of the absorption line of the harmless marked gas (such as water vapor and oxygen) in the background gas is utilized to deduce the position of the harmful absorption line of the gas to be measured, and then the laser parameter is adjusted; then, a standard tool is placed in the target system, the nonlinear representation of the scanning wavelength of the laser of the target system is obtained, the curve relation between the direct absorption signal of the target system and the scanning time and the curve relation between the direct absorption signal of the target system and the scanning wavelength are obtained according to the difference of the nonlinear representations of the scanning wavelengths of the laser of the reference system and the laser of the target system and the direct absorption signal of the gas of the reference system, and then the calibration coefficient calculated by the concentration of the measured gas of the target system is obtained; the etalon is used as a conversion medium, standard gas does not need to be introduced, the problems of pollution caused by the standard gas, difficulty in storage, difficulty in transportation and the like can be solved, and the efficiency of calibrating the batch target system can be improved.
Optionally, the step of obtaining a direct absorption signal generated by an etalon based on an etalon positioned between a transmitting module and a receiving module of the reference system comprises:
determining laser parameters of a reference system based on the absorption spectral line range of the measured gas, wherein the laser parameters comprise a scanning current minimum reference value, a scanning current maximum reference value and a laser temperature;
the method comprises the steps of obtaining the temperature, the pressure and the gas direct absorption signal peak value of standard gas introduced between a transmitting module and a receiving module of a reference system, and obtaining a calibration coefficient calculated by the concentration of the measured gas based on the temperature, the pressure and the direct absorption signal peak value of the standard gas.
By adopting the technical scheme, when the laser parameter of the reference system is determined, the standard gas is required to be introduced between the transmitting module and the receiving module of the reference system, the parameter of the laser is adjusted according to the spectral line range of the standard gas, so that the output laser wavelength range of the laser corresponds to the absorption spectral line when the standard gas is introduced, the peak value of the absorption signal output by the reference system is obtained, and then the conversion relation between the temperature, the pressure and the peak value of the measured gas and the standard gas concentration is determined, so that the calibration coefficient of the measured gas concentration in the reference system is obtained for the calibration reference of the subsequent target system.
Optionally, after the step of obtaining the calibration coefficient calculated by the concentration of the measured gas based on the temperature, the pressure and the direct absorption signal peak value of the standard gas, the method comprises:
changing laser current parameters of a reference system, multiplying a lowest reference value of scanning current by a first preset multiple, and multiplying a highest reference value of scanning current by a second preset multiple, wherein the first preset multiple is a real number smaller than 1, and the second preset multiple is a real number larger than 1.
By adopting the technical scheme, the reference system is only a reference standard, and the lowest current value and the highest current value of the scanning current are respectively multiplied by corresponding multiples, so that the scanning range of the scanning current can be expanded, the coverage range of the reference system can be enlarged, the reference system can be suitable for lasers of some target systems beyond the scanning current range, and the reference system can be suitable for calibrating more target systems.
Optionally, the step of obtaining a non-linear characterization of the laser scanning wavelength of the reference system includes:
acquiring a scanning wavelength interval delta V = 1/(2 nL) between two adjacent wave peaks of the etalon based on the physical characteristics of the etalon and a direct absorption signal generated by the etalon, wherein n is the material refractive index of the etalon, and L is the physical size of the etalon;
obtaining the scanning time interval on the change curve of the direct absorption signal generated by the etalon along with the scanning time by taking the scanning wavelength interval delta V between two adjacent wave crests as a standard;
and describing a change curve of the scanning wavelength along with the scanning time of the reference system by taking the scanning time interval as an abscissa and taking the scanning wavelength interval as an ordinate, and obtaining the nonlinear representation of the laser scanning wavelength of the reference system.
By adopting the technical scheme, the laser has nonlinear characterization, namely the scanning wavelength and the scanning time of the laser are not in a linear relationship, the nonlinear characterization of the laser is quantitatively characterized by utilizing the etalon, and a relation change curve of the scanning wavelength and the scanning time of the laser of the reference system is embodied in a form of a coordinate system, so that a bridge can be established between the reference system and a target system, and the relation between the nonlinear characteristics of the two lasers or the difference between the nonlinear characteristics of the two lasers can be measured or quantified.
Optionally, the step of obtaining the curve relationship between the gas direct absorption signal of the target system and the scanning time and the scanning wavelength respectively includes:
acquiring the curve relation between the gas direct absorption signal of the target system and the scanning wavelength by an interpolation method based on the curve relation between the gas direct absorption signal and the scanning wavelength obtained when the standard gas is introduced in the calibration process of the reference system and the curve relation of the nonlinear representation of the scanning wavelength of the target system;
and acquiring the curve relation between the gas direct absorption signal of the target system and the scanning time by a spectrum simulation method based on the curve relation between the gas direct absorption signal of the target system and the scanning wavelength.
By adopting the technical scheme, in order to obtain the curve relationship between the direct absorption signal and the scanning time of the target system, the curve relationship between the gas direct absorption signal and the scanning wavelength of the target system needs to be obtained first, and on the coordinate system of the curve relationship between the gas direct absorption signal and the scanning wavelength of the target system, data in the prediction range can be conveniently predicted through data at two ends of the known range by an interpolation method, then the curve relationship between the gas direct absorption signal and the scanning time of the target system is obtained by a spectral simulation method, and then the peak value of the direct absorption signal of the target system is obtained on the curve between the direct absorption signal and the scanning time of the target system, so as to calculate the calibration coefficient for calculating the concentration of the measured gas of the target system.
Optionally, the step of obtaining a direct absorption signal peak of the target system includes:
acquiring curve relations between direct absorption signals of a target system and scanning time and scanning wavelength respectively, and performing digital filtering on the direct absorption signals of the target system, wherein digital filtering parameters of the target system are the same as those of a reference system;
and acquiring a direct absorption signal peak value of the target system based on the digitally filtered direct absorption signal of the target system.
By adopting the technical scheme, because the signal-to-noise ratio of the direct absorption signal of the target system calculated by the interpolation method is low, the direct absorption signal of the target system is subjected to noise reduction treatment in a digital filtering mode, and the accuracy of the direct absorption signal peak value of the target system is improved.
In a second aspect, the application provides a calibration apparatus for a laser gas analysis system, which adopts the following technical scheme:
a calibration device of a laser gas analysis system comprises a memory and a processor;
the memory is used for storing a program for calibrating the laser gas analysis system;
the processor is used for executing the laser gas analysis system calibration method when the program stored in the memory for calibrating the laser gas analysis system is operated.
By adopting the technical scheme, when laser emitted by the laser passes through the etalon, the receiving module receives a direct absorption signal after the laser absorbs partial light by the etalon, a nonlinear representation of the laser scanning wavelength of the reference system can be obtained, laser parameters of the target system are determined based on the absorption spectrum range of the gas to be measured, then the etalon is placed between the emitting module and the receiving module in the target system, the nonlinear representation of the laser scanning wavelength of the target system is obtained based on the etalon measurement parameters and output data, then the incidence relation between the peak value of the absorption peak output by the target system and the recording parameters in the process of introducing the standard gas into the reference system is obtained according to the difference between the nonlinear representation of the target system and the nonlinear representation of the reference system, and the calibration coefficient calculated on the concentration of the gas to be measured after the reference system is introduced with the standard gas is known, the calibration coefficient of the measured gas concentration calculation of the target system can be obtained, the known parameters of the reference system and the etalon are used as the conversion standard to calibrate other target systems with the same model, calibration is carried out without introducing standard gas, and the calibration efficiency of the batch measurement system is improved conveniently.
In a third aspect, the present application provides a calibration system for a laser gas analysis system, which adopts the following technical scheme:
a calibration system of a laser gas analysis system comprises a target system, a reference system, an etalon and a calibration device of the laser gas analysis system, wherein the reference system and the target system respectively comprise a transmitting module and a receiving module, the transmitting module comprises a laser, a driving circuit and an optical collimating lens, and the receiving module comprises an optical converging lens, a detector and a digital signal processing circuit;
the reference system is used for playing a reference role in the calibration of the target system;
the target system is used for measuring the laser parameters of the target system through the reference system and the etalon;
the laser is arranged on the transmitting module and used for transmitting laser beams to be received by the receiving module;
the driving circuit is in communication connection with the laser and is used for driving the laser through current and controlling the temperature of the laser;
the optical collimating lens is used for converting laser beams emitted by the laser in a divergent state into collimated beams transmitted in a parallel state;
the optical converging lens is used for converging the laser beams and projecting the converged laser beams onto the detector;
the detector is used for converting the received optical signal into an electric signal and sending the electric signal to the digital signal processing circuit;
the input end of the digital signal processing circuit is in communication connection with the detector, the output end of the digital signal processing circuit is connected with the upper computer, and the digital signal processing circuit is used for performing signal processing on the acquired spectral signals, calculating the concentration value of the gas and then transmitting the concentration value to the upper computer;
the etalon is used for measuring the corresponding relation between the direct absorption signal of the reference system and the scanning wavelength, and then obtaining the corresponding relation between the direct absorption signal of the target system and the scanning wavelength according to the nonlinear representation of the laser of the reference system and the nonlinear representation of the laser of the target system.
By adopting the technical scheme, when a laser beam emitted by the laser passes through the etalon, the optical collimating lens is used for converting the laser beam emitted by the laser in a divergent state into a collimated beam transmitted in a parallel state, the optical converging lens is used for converging the laser beam and projecting the converged laser beam to the detector, the detector is used for converting a received optical signal into an electric signal and transmitting the electric signal to the digital signal processing circuit, the digital signal processing circuit forms a direct absorption signal to obtain the nonlinear representation of the laser scanning wavelength of the reference system, the laser parameter of the target system is determined based on the absorption spectrum range of the gas to be measured, then the etalon is placed between the emitting module and the receiving module in the target system, the nonlinear representation of the laser scanning wavelength of the target system is obtained based on the etalon measurement parameter and the output data, and then, according to the difference between the nonlinear representation of the target system and the nonlinear representation of the reference system, obtaining the incidence relation between the peak value of the absorption peak output by the target system and the recording parameter of the reference system in the process of introducing standard gas into the reference system, and calibrating other target systems of the same model by using the known parameter of the reference system and the etalon as conversion standards without introducing standard gas for calibration, so that the calibration efficiency of the batch measurement system is improved conveniently.
Optionally, the system further includes a signal amplifier, an input end of the signal amplifier is in communication connection with the detector, and an output end of the signal amplifier is in communication connection with the digital signal processing circuit, and is configured to amplify the received laser beam and send the amplified laser beam to the digital signal processing circuit.
By adopting the technical scheme, because the laser beam emitted by the laser device can lose part in the transmission process, when the detector detects the laser signal, the signal amplifier amplifies the spectrum signal, and the definition and the accuracy of directly absorbing the signal spectrum line are improved.
To sum up, the application comprises the following beneficial technical effects:
when the system is calibrated, calibration gas is not needed to be used for calibration, calibration of other target systems to be measured is realized by setting a reference system with known parameters and the etalon as the intermediate conversion standard, and the calibration method has the effect of improving the calibration efficiency of batch measurement systems conveniently.
Drawings
Fig. 1 is a schematic hardware architecture diagram of a calibration system of a laser gas analysis system according to an embodiment of the present disclosure.
Fig. 2 is a flowchart of a calibration method of a laser gas analysis system according to an embodiment of the present application.
Fig. 3 is an expanded flowchart of S200 in fig. 2.
FIG. 4 is a graph of direct absorption signals of a calibration system of a laser gas analysis system according to an embodiment of the present application.
Fig. 5 is a flowchart of the expansion of S300 in fig. 2.
FIG. 6 is a scanning wavelength scan graph of a calibration system of a laser gas analysis system according to an embodiment of the present application.
Fig. 7 is a graph of measured gas direct absorption signal versus scanning wavelength for a reference system and a target system of a calibration system of a laser gas analysis system according to an embodiment of the present application.
Fig. 8 is a flowchart of the expansion of S400 in fig. 2.
Fig. 9 is a flowchart of the expansion of S500 in fig. 2.
FIG. 10 is a graph of measured gas absorption signal versus scan time after filtering for a calibration system of a laser gas analysis system according to an embodiment of the present disclosure.
Description of reference numerals: 1. a transmitting module; 2. a receiving module; 3. an etalon; 4. a laser; 5. a drive circuit; 6. an optical collimating lens; 7. an optical converging lens; 8. a detector; 9. a signal amplifier; 10. a digital signal processing circuit.
Detailed Description
The present application is described in further detail below with reference to all of the following figures.
The embodiment of the application discloses a laser gas analysis system calibration system. A laser gas analysis system calibration system comprises a target system, a reference system, an etalon 3 and a laser gas analysis system calibration device.
The reference system is used for performing reference function on calibration of the target system.
After the introduction of the standard gas into the reference system is finished, the etalon 3 is placed in the reference system to obtain a direct absorption signal of the reference system, then a nonlinear representation of the laser 4 of the reference system is obtained, and then the etalon 3 is placed in the target system to obtain a nonlinear representation of the laser 4 of the target system, wherein a fabry-perot (F-P) high-precision standard 3 is adopted in the embodiment.
The target system is used to measure its own laser 4 parameters via the reference system and etalon 3.
The laser gas analysis system calibration device comprises a memory and a processor, wherein the memory is used for storing a program calibrated to the laser gas analysis system, the memory comprises hardware with a storage function, such as a cf flash memory card, an sm flash memory card, an sd flash memory card, an xd flash memory card, an mmc flash memory card, a micro hard disk and the like, the processor is used for executing the program calibrated to the laser gas analysis system, the processor comprises a single chip microcomputer, an MCU, a central processing unit and other chips and the like, and a 32-bit low-power consumption single chip microcomputer is generally used.
Referring to fig. 1, the reference system and the target system each include a transmission module 1 and a reception module 2, the transmission module 1 including a laser 4, a driving circuit 5, and an optical collimating lens 6, and the reception module 2 including an optical converging lens 7, a detector 8, a signal amplifier 9, and a digital signal processing circuit 10.
The laser 4 is used for emitting laser beams for receiving by the receiving module 2.
The driving circuit 5 is in communication connection with the laser 4 and is used for driving the laser 4 through current and controlling the temperature of the laser.
The optical collimating lens 6 is arranged on one side of the laser 4 close to the receiving module 2 and is used for converting the laser beam emitted by the laser 4 in a divergent state into a collimated beam transmitted in a parallel state.
The optical converging lens 7 is disposed on a side of the detector 8 close to the emitting module 1, and is used for converging the laser beam and projecting the converged laser beam onto the detector 8.
The detector 8 is used for converting the received optical signal into an electrical signal, amplifying the electrical signal by the signal amplifier 9 and sending the amplified electrical signal to the digital signal processing circuit 10.
The input end of the signal amplifier 9 is connected with the output end of the detector 8 in a communication manner, and the output end of the signal amplifier 9 is connected with the digital signal processing circuit 10 in a communication manner, and is used for receiving the electric signal sent by the detector 8 and carrying out amplification processing.
And the input end of the digital signal processing circuit 10 is in communication connection with the signal amplifier 9, the output end of the digital signal processing circuit is connected with a PC (personal computer) end upper computer, and the digital signal processing circuit is used for processing the direct absorption signal spectral line received by the detector 8 and amplified by the signal amplifier 9 into a more accurate direct absorption signal spectral line, calculating the concentration value of the gas and transmitting the concentration value to the PC end upper computer.
The implementation principle of the calibration system of the laser gas analysis system in the embodiment of the application is as follows: before a target system is calibrated, a reference system is calibrated by using a standard gas, the standard gas is introduced into the reference system, parameters of a laser 4 of the reference system are determined according to a direct absorption signal peak value, a calibration coefficient of the concentration of the measured gas of the reference system is obtained, then a nonlinear representation of the scanning wavelength of the laser 4 of the reference system is obtained by using an etalon 3, then the etalon 3 is placed between a transmitting module 1 and a receiving module 2 in the target system, the nonlinear representation of the scanning wavelength of the laser 4 of the target system is obtained based on the measurement parameters and output data of the etalon 3, the direct absorption signal peak value of the target system is obtained according to the nonlinear representation of the scanning wavelength of the laser 4 of the target system, then the calibration coefficient of the concentration of the measured gas of the reference system is used according to the difference between the nonlinear representation of the target system and the nonlinear representation of the reference system, the calibration coefficient of the measured gas concentration of the target system is obtained, and the calibration of the target system is realized.
Referring to fig. 2, based on the hardware architecture, the embodiment further discloses a calibration method for a laser gas analysis system, which includes steps S100 to S700:
step S100: based on the absorption line range of the measured gas, laser 4 parameters of the reference system are determined, the laser 4 parameters including a scan current minimum reference value, a scan current maximum reference value and a laser 4 temperature.
When the reference system is calibrated, the measured gas is introduced into the reference system, the concentration and the absorption spectral line range of the measured gas are known, and according to the absorption spectral line range, the laser parameter of the reference system is adjusted to control the output laser wavelength range of the laser, so that the wavelength range is consistent with the absorption spectral line range of the measured gas, and the determination of the laser parameter of the reference system is realized.
S200, placing a sample pool with sealed standard gas between a transmitting module 1 and a receiving module 2 of a reference system, introducing the standard gas into the sample pool, and carrying out calibration recording; the gas temperature T, the pressure P and the peak A0_ ref of the spectral signal φ (T, P) are recorded, and the calibration coefficient η _ ref calculated for the measured gas concentration is determined.
It should be noted that, since the standard gas is affected by the concentration, the pressure and the temperature at the same time, not only the concentration of the standard gas is calibrated, but also the pressure and the temperature of the standard gas can be calibrated, so that the calibration of the standard gas is optimized.
As mentioned above, a conversion relation of the ratio of the peak signal amount to the standard gas concentration is established according to the temperature and the pressure of the standard gas and the direct absorption signal peak value a0_ ref, for example, a standard gas concentration of 1000ppm corresponds to a peak signal amount of 1000mv, and then a calibration coefficient η _ ref =1ppm/mv calculated according to the standard gas concentration and the signal amount corresponding to the standard gas peak value is obtained.
Referring to FIG. 3, the step S200 includes steps S210 to S220:
step S210: changing current parameters of a laser 4 of a reference system, multiplying a lowest reference value of scanning current by a first preset multiple, and multiplying a highest reference value of scanning current by a second preset multiple, wherein the first preset multiple is a real number smaller than 1, and the second preset multiple is a real number larger than 1.
For example, the first predetermined multiple multiplied by the minimum scan current value imin _ ref is 0.8, and the second predetermined multiple multiplied by the maximum scan current value imax _ ref is 1.2, so that the minimum scan current value imin _ extended = imin _ ref 1.2 and the maximum scan current value imax _ extended = imax _ ref 1.2 can expand the comparison range between the target system and the reference system.
Step S220: placing the etalon 3 between the transmitting unit and the receiving unit, and obtaining a direct absorption signal generated by the etalon 3 through the signal processing circuit 10; based on the physical characteristics of the etalon 3 and the direct absorption signal of the etalon 3, a scanning wavelength interval Δ V = 1/(2 nL) between two adjacent peaks of the etalon 3 is obtained, where n is the material refractive index of the etalon 3 and L is the physical size of the etalon 3.
Since the etalon 3 is used as a measuring tool, the refractive index of the material and the physical dimension thereof are known, where the physical dimension refers to the thickness of the etalon 3, and the scanning wavelength interval Δ vfp between two adjacent peaks is equivalent to the scale interval on the scale, and is a fixed value, and the scanning wavelength output by the laser 4 of different target systems can be measured by using the fixed value.
Referring to fig. 2, step S300: the non-linear characterization of the laser 4 scanning wavelength of the reference system is obtained based on the etalon 3 measurement parameters and the output data.
Referring to fig. 4, the signal intensity (vertical axis) of the etalon 3 is plotted against the scanning time (horizontal axis), and the scanning time interval on the horizontal axis is the same, but in the figure, the visual size of the scanning wavelength interval Δ vfp between two adjacent peak peaks is not the same due to the nonlinear relationship of the laser 4.
Referring to FIG. 5, step S300 includes steps S310 to S320:
step S310: the method comprises the steps of obtaining a direct absorption signal generated by an etalon 3 based on the etalon 3 placed between a transmitting module 1 and a receiving module 2 of a reference system, and obtaining a nonlinear representation of a scanning wavelength of a laser 4 of the reference system based on the direct absorption signal and a scanning wavelength interval between two adjacent wave peaks determined by physical characteristics of the etalon 3.
The step S310 includes steps S31A-S31B:
step S31A: and obtaining the scanning time interval by taking the scanning wavelength interval between two adjacent peaks as a standard.
Step S31B: and describing a change curve of the scanning wavelength along with the scanning time of the reference system by taking the scanning time interval as an abscissa and taking the scanning wavelength interval as an ordinate, and obtaining the nonlinear representation of the scanning wavelength of the laser 4 of the reference system.
Referring to fig. 6, when obtaining the non-linear curve of the scanning wavelength of the laser 4 of the reference system, it is necessary to accumulate the scanning wavelength interval Δ vfp of the etalon 3 in each of the same scanning time periods, and since the scanning time periods corresponding to each of the same scanning wavelength intervals Δ vfp are not uniform, the slope of the curve exhibited when the scanning wavelength v _ ref of the laser 4 of the reference system on the ordinate is accumulated with the scanning time t is not uniform.
Step S320: based on the nonlinear characterization of the scanning wavelength of the laser 4 and the direct absorption signal generated by the etalon 3, the curve relation between the direct absorption signal of the reference system and the scanning wavelength of the laser 4 is obtained.
Referring to fig. 7, which is a graph of the direct absorption signal of the reference system versus the scanning wavelength of the laser 4, the abscissa is the scanning wavelength v _ ref and the ordinate is the system direct absorption signal S _ ref (v _ ref).
Referring to fig. 2, step S400: the laser 4 parameters of the target system are determined based on the absorption line range of the measured gas in the background gas.
Referring to FIG. 8, step S400 includes steps S410 to S420:
step S410: the laser 4 of the target system is adjusted by using the absorption spectrum line of the background gas or using a wavemeter with the wavelength position of the absorption peak of the measured gas as a reference.
Step S420: and acquiring parameters of the laser 4 of the target system, wherein the parameters of the laser 4 comprise a scanning current minimum reference value, a scanning current maximum reference value and the temperature of the laser 4.
When the target system is calibrated, the current parameter and the temperature parameter of the laser 4 of the target system are adjusted and determined by finding the wavelength position of the absorption peak of the measured gas (such as hydrogen sulfide) through the absorption line of the background gas (such as air) in the environment or by using a wavelength meter.
Referring to fig. 2, step S500: and obtaining the nonlinear representation of the scanning wavelength of the laser 4 of the target system based on the etalon 3 measurement parameters and the output data.
Referring to FIG. 9, step S500 includes steps S510 to S530:
step S510: the method comprises the steps of obtaining a direct absorption signal generated by an etalon 3 based on the etalon 3 arranged between a transmitting module 1 and a receiving module 2 of a target system, and obtaining a nonlinear representation of a scanning wavelength of a laser 4 of the target system based on the direct absorption signal and a scanning wavelength interval between two adjacent wave peaks determined by physical characteristics of the etalon 3.
Referring to fig. 4, similar to the non-linear characterization of the scanning wavelength of the laser 4 of the reference system, the scanning wavelength intervals Δ vfp of the etalon 3 in each of the same scanning time periods need to be accumulated, and since the scanning time periods corresponding to each of the same scanning wavelength intervals Δ vfp are not uniform, the slope of the curve presented when the scanning wavelength v _ target of the laser 4 of the target system on the ordinate is accumulated with the scanning time t is not uniform.
Step S520: and acquiring curve relations between the direct absorption signal and the scanning time of the target system and between the direct absorption signal and the scanning wavelength based on the nonlinear characterization of the scanning wavelength of the laser 4 of the reference system and the nonlinear characterization of the scanning wavelength of the laser 4 of the target system.
The step S520 includes steps S52A-S52B:
step S52A: and acquiring the curve relation between the direct absorption signal of the target system and the scanning wavelength by an interpolation method based on the curve relation between the direct absorption signal of the gas obtained when the standard gas is introduced in the calibration process of the reference system and the nonlinear representation of the scanning time and the scanning wavelength.
Referring to fig. 7, since the interpolation method for the nonlinear characterization of the scanning wavelength of the laser 4 of the reference system and the nonlinear characterization of the scanning wavelength of the laser 4 of the target system can only be performed in the form of the scanning wavelength as an independent variable, when obtaining the curve relationship S _ target (v _ target) between the direct absorption signal and the scanning wavelength of the target system, it depends on the combination of the curve relationship S _ ref (v _ ref) between the direct absorption signal and the scanning wavelength obtained in the calibration process of the reference system passing the standard gas and the curve relationship of the nonlinear characterization of the scanning wavelength of the target system.
Step S52B: and acquiring the curve relation between the direct absorption signal of the target system and the scanning time by a spectrum simulation method based on the curve relation between the direct absorption signal of the target system and the scanning wavelength.
Since the peak signal peak value a0_ target of the direct absorption signal of the target system needs to be converted into a coordinate system with the scanning time t as the abscissa, the curve relationship S _ target (v _ target) between the direct absorption signal of the target system and the scanning wavelength needs to be converted into the curve relationship S _ target (t) between the direct absorption signal of the target system and the scanning time.
Step S530: and acquiring the peak value of the direct absorption signal in the curve relation between the direct absorption signal of the target system and the scanning time based on the curve relation between the direct absorption signal of the target system and the scanning time and the scanning wavelength respectively.
Referring to fig. 10, a more accurate peak value a0_ target of the direct absorption signal is obtained through a curve relation S _ target (t) between the direct absorption signal of the target system and the scanning time, and then the direct absorption signal is subjected to noise reduction processing in a digital filtering manner through a signal processing circuit.
The step S530 includes steps S53A-S53B:
step S53A: and acquiring curve relations between the direct absorption signal of the target system and the scanning time and the scanning wavelength respectively, and performing digital filtering on the direct absorption signal of the target system, wherein the digital filtering parameters of the target system are the same as those of the reference system.
Step S53B: and acquiring a direct absorption signal peak value of the target system based on the digitally filtered direct absorption signal of the target system.
Referring to fig. 10, the direct absorption signal S _ target (T) of the target system contains a large noise signal, so digital filtering is required to filter the direct absorption signal S _ target (T) of the target system into a more accurate direct absorption signal Φ _ target (T, P), and then obtain the direct absorption signal peak a0_ target.
Step S600: and obtaining the incidence relation between the peak value output by the target system and the recording parameter in the standard gas introducing process of the reference system based on the difference between the nonlinear representation of the target system and the nonlinear representation of the reference system.
Step S700: and acquiring a calibration coefficient calculated by the concentration of the measured gas of the target system based on the incidence relation of the recorded parameters of the peak value output by the target system in the calibration process of the reference system and the calibration coefficient calculated by the reference system for the concentration of the measured gas.
The following formula is satisfied when a calibration coefficient η _ target calculated for the measured gas concentration of the target system is obtained, and the calibration coefficient η _ target = η _ ref a0_ target/a0_ ref calculated for the measured gas concentration of the target system is obtained, so that the target system is calibrated by using the calibration coefficient η _ target instead of the standard gas.
The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.
Claims (9)
1. A calibration method of a laser gas analysis system is characterized by comprising the following steps: calibrating a target system with lasers of the same type by a reference system calibrated by a calibration gas, comprising:
obtaining a non-linear characterization of the laser (4) scanning wavelength of the reference system based on the etalon (3) measurement parameters and the output data;
acquiring laser (4) parameters for determining a target system based on the absorption spectral line range of a detected gas in background gas;
obtaining a nonlinear representation of the scanning wavelength of a laser (4) of a target system based on the etalon (3) measurement parameters and output data;
obtaining an incidence relation between a peak value of an absorption peak output by the target system and a recording parameter in the standard gas introducing process of the reference system based on the difference between the nonlinear representation of the target system and the nonlinear representation of the reference system;
obtaining the correlation between the peak value of the absorption peak output by the target system and the recording parameter of the reference system in the process of introducing the standard gas, and the calibration coefficient of the reference system for calculating the concentration of the measured gas, and obtaining the calibration coefficient of the target system for calculating the concentration of the measured gas;
the step of obtaining a non-linear characterization of the laser (4) scanning wavelength of the reference system comprises:
setting an etalon (3) between a transmitting module (1) and a receiving module (2) of a reference system, acquiring a direct absorption signal generated by the etalon (3), and acquiring a nonlinear representation of a scanning wavelength of a laser (4) of the reference system based on the direct absorption signal and a scanning wavelength interval between two adjacent wave peaks determined by physical characteristics of the etalon (3);
acquiring a curve relation between a gas direct absorption signal of the reference system and the scanning wavelength of the laser (4) based on the nonlinear representation of the scanning wavelength of the laser (4) of the reference system and the gas direct absorption signal corresponding to the introduced standard gas of the reference system;
the step of determining laser (4) parameters of the target system comprises:
adjusting a laser (4) of a target system by using an absorption spectrum line of background gas or a wavelength meter and taking the wavelength position of an absorption peak of the gas to be detected as a reference, and obtaining parameters of the laser (4) of the target system, wherein the parameters of the laser (4) comprise a scanning current minimum reference value, a scanning current maximum reference value and the temperature of the laser (4);
the step of obtaining a non-linear characterization of the laser (4) scanning wavelength of the target system comprises:
based on placing an etalon (3) between a transmitting module (1) and a receiving module (2) of a target system, acquiring a direct absorption signal generated by the etalon (3), and based on the direct absorption signal and a scanning wavelength interval between two adjacent wave peaks determined by physical characteristics of the etalon (3), acquiring a nonlinear characterization of a scanning wavelength of a laser (4) of the target system;
the step of obtaining the incidence relation between the peak value of the absorption peak output by the target system and the recording parameter in the process of introducing the standard gas into the reference system comprises the following steps:
acquiring curve relations between gas direct absorption signals of the target system and scanning time and scanning wavelength respectively based on nonlinear representation of scanning wavelength of the laser (4) of the reference system and nonlinear representation of scanning wavelength of the laser (4) of the target system;
obtaining the peak value of a gas direct absorption signal corresponding to the introduced standard gas in the target system based on the curve relation between the gas direct absorption signal of the target system and the scanning time;
the step of obtaining calibration coefficients for the target system's measured gas concentration calculation includes:
and acquiring the calibration coefficient calculated by the concentration of the measured gas of the target system based on the peak value of the direct gas absorption signal of the target system, the calibration coefficient calculated by the concentration of the measured gas of the reference system and the peak value of the direct gas absorption signal corresponding to the introduced standard gas in the reference system.
2. The method for calibrating a laser gas analysis system according to claim 1, wherein: the step of obtaining a direct absorption signal generated by an etalon (3) based on placing the etalon (3) between a transmitting module (1) and a receiving module (2) of a reference system, comprises, before:
determining laser (4) parameters of a reference system based on the absorption line range of the measured gas, wherein the laser (4) parameters comprise a scanning current minimum reference value, a scanning current maximum reference value and a laser (4) temperature;
the method comprises the steps of obtaining the temperature, the pressure and the gas direct absorption signal peak value of standard gas introduced between a transmitting module (1) and a receiving module (2) of a reference system, and obtaining a calibration coefficient calculated by the concentration of the measured gas based on the temperature, the pressure and the direct absorption signal peak value of the standard gas.
3. The method for calibrating a laser gas analysis system according to claim 2, wherein: the method comprises the following steps of obtaining a calibration coefficient calculated by the concentration of the measured gas based on the temperature, the pressure and the direct absorption signal peak value of the standard gas:
changing the current parameter of a laser (4) of a reference system, multiplying the lowest reference value of the scanning current by a first preset multiple, and multiplying the highest reference value of the scanning current by a second preset multiple, wherein the first preset multiple is a real number smaller than 1, and the second preset multiple is a real number larger than 1.
4. The method for calibrating a laser gas analysis system according to claim 1, wherein: the step of obtaining a non-linear characterization of the laser (4) scanning wavelength of the reference system comprises:
acquiring a scanning wavelength interval delta V = 1/(2 nL) between two adjacent wave peaks of the etalon (3) based on the physical characteristics of the etalon (3) and a direct absorption signal generated by the etalon (3), wherein n is the material refractive index of the etalon (3), and L is the physical size of the etalon (3);
obtaining the scanning time interval on the change curve of the direct absorption signal generated by the etalon along with the scanning time by taking the scanning wavelength interval delta V between two adjacent wave crests as a standard;
and describing a change curve of the scanning wavelength along with the scanning time of the laser of the reference system by taking the scanning time interval as an abscissa and taking the scanning wavelength interval as an ordinate, thereby obtaining the nonlinear representation of the scanning wavelength of the laser (4) of the reference system.
5. The method for calibrating a laser gas analysis system according to claim 1, wherein: the step of obtaining the curve relation between the gas direct absorption signal of the target system and the scanning time and the scanning wavelength respectively comprises the following steps:
acquiring the curve relation between the gas direct absorption signal of the target system and the scanning wavelength by an interpolation method based on the curve relation between the gas direct absorption signal and the scanning wavelength obtained when the standard gas is introduced in the calibration process of the reference system and the curve relation between the gas direct absorption signal and the nonlinear representation of the scanning wavelength of the target system;
and acquiring the curve relation between the gas direct absorption signal of the target system and the scanning time by a spectrum simulation method based on the curve relation between the gas direct absorption signal of the target system and the scanning wavelength.
6. The method for calibrating a laser gas analysis system according to claim 5, wherein: the step of obtaining the peak value of the direct gas absorption signal corresponding to the introduced standard gas in the target system comprises the following steps:
acquiring curve relations between gas direct absorption signals of a target system and scanning time and scanning wavelength respectively, and performing digital filtering on the gas direct absorption signals of the target system, wherein digital filtering parameters of the target system are the same as those of a reference system;
and acquiring a gas direct absorption signal peak value of the target system based on the digitally filtered gas direct absorption signal of the target system.
7. The utility model provides a laser gas analysis system calibration device which characterized in that: comprising a memory and a processor;
the memory is used for storing a program for calibrating the laser gas analysis system;
the processor is used for executing the laser gas analysis system calibration method as claimed in any one of the claims 1 to 6 when the program stored in the memory is used for storing a program for calibrating the laser gas analysis system.
8. A laser gas analysis system calibration system is characterized in that: the calibration device comprises a target system, a reference system, an etalon (3) and the laser gas analysis system calibration device of claim 7, wherein the reference system and the target system both comprise a transmitting module (1) and a receiving module (2), the transmitting module (1) comprises a laser (4), a driving circuit (5) and an optical collimating lens (6), and the receiving module (2) comprises an optical converging lens (7), a detector (8) and a digital signal processing circuit (10);
the reference system is used for playing a reference role in the calibration of the target system;
the target system is used for measuring the parameters of the laser (4) through the reference system and the etalon (3);
the laser (4) is arranged on the transmitting module (1) and used for transmitting laser beams to be received by the receiving module (2);
the driving circuit (5) is in communication connection with the laser (4) and is used for driving the laser (4) to emit scanning current and controlling the temperature of the laser;
the optical collimating lens (6) is used for converting a laser beam emitted by the laser (4) in a divergent state into a collimated beam transmitted in a parallel state;
the optical converging lens (7) is used for converging the laser beam and projecting the converged laser beam onto the detector (8);
the detector (8) is used for converting the received optical signal into an electric signal and sending the electric signal to the digital signal processing circuit (10);
the input end of the digital signal processing circuit (10) is in communication connection with the detector (8), the output end of the digital signal processing circuit is connected with the upper computer, and the digital signal processing circuit is used for performing signal processing on the acquired spectral signals, calculating the concentration value of the gas and then transmitting the concentration value to the upper computer;
the etalon (3) is used for measuring the corresponding relation between the direct absorption signal of the reference system and the scanning wavelength, and then obtaining the corresponding relation between the direct absorption signal of the target system and the scanning wavelength according to the nonlinear representation of the laser (4) of the reference system and the nonlinear representation of the laser (4) of the target system.
9. The system for calibrating a laser gas analysis system according to claim 8, wherein: the system further comprises a signal amplifier (9), wherein the input end of the signal amplifier (9) is in communication connection with the detector (8), and the output end of the signal amplifier (9) is in communication connection with the digital signal processing circuit (10) and is used for amplifying the received laser beam and sending the amplified laser beam to the digital signal processing circuit (10).
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