CN112782126A - Telemetering calibration-free fire early-stage characteristic gas detection device and online demodulation method - Google Patents
Telemetering calibration-free fire early-stage characteristic gas detection device and online demodulation method Download PDFInfo
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Abstract
A remote measuring type calibration-free fire early characteristic gas detection device and an online demodulation method thereof belong to the technical field of fire detection, and solve the problems that the existing air suction type fire early gas detection device is small in space detection range and the traditional remote measuring type fire early gas detection needs periodic calibration The response of the photodetector and the effect of changes in the reflectance of the target on the measurement results.
Description
Technical Field
The invention belongs to the technical field of fire detection, and relates to a telemetering calibration-free fire early-stage characteristic gas detection device and an online demodulation method thereof.
Background
At present, in the field of fire early warning and detection, a widely applied fire detector is a typical point-type smoke-sensitive fire detector, the detector is easy to miss and report false alarms due to an optical labyrinth structure, and has low detection sensitivity, low precision, slow response and small detection range.
The development trend of future fire detectors is to realize early warning, so that the significance of researching and developing early fire alarm technology is great, and the main guiding concept of early fire alarm is as follows: firstly, the advanced technology is adopted, the detection sensitivity is improved, and the detection alarm can be realized when few products are generated in the early stage of the fire; and secondly, detecting the products of the fire which is not formed in the fire process, such as early fire characteristic gas. The application space of the early fire alarm technology is large, and the technology is researched and developed, so that the progress and development of a novel fire early detection technology are facilitated.
The gas detection method is adopted to detect various characteristic trace gases (CO, CO2 and HCN) discharged in the early stage of fire, so that the early warning function of fire can be realized. In the prior art, a fire disaster gas sampling mode is measured by adopting a pump suction mode in Chinese patent application No. CN201610908348.X with publication date of 2017, 3 and 22 days, in a multi-gas parallel trace detection fire early warning device and method, in Chinese patent application No. CN201010214367.5 with publication date of 2010, 11 and 24 days, in a three-component fire disaster gas detector, in Chinese utility model patent No. CN201720136960.X with publication date of 2017, 11 and 3 days, in an extreme early stage gas suction type fire disaster detector, in Chinese patent application No. CN201620217990.9 with publication date of 2017, 11 and 3 days, in Chinese invention patent application No. CN201710765198.6 with publication date of 2017, 11 and 07 days, in the traditional gas suction type fire disaster detector is point contact measurement, the method has the advantages of complex measurement system, small spatial measurement range, easy report omission and slow response.
The traditional gas detection technologies such as semiconductor gas detectors, electrochemical gas sensors, contact gas sensors and the like have inherent defects such as low detection sensitivity, low precision, slow response, poor stability, need of regular calibration and the like, and in early fire warning, the requirements for rapid and high-precision monitoring of trace gas discharged in the early fire stage are difficult to meet.
The remote-measuring fire gas detection has the advantages of large space detection range, non-contact measurement, difficult missing report, quick response and obvious advantages in the field of early detection of fire. For example, the chinese utility model patent "a fire early warning system based on laser remote sensing measurement" with application number CN201721298862.2 and publication date of 2017, 11, 3 days has the characteristics of high sensitivity, good reliability and strong anti-interference capability, but the technical scheme of the invention patent has the problems of not compact overall structure, short space detection distance, only 10m, not meeting the fire detection requirement of high and large space buildings (more than 12m), and needing regular calibration for long-time measurement, and the like, and cannot meet the practical application requirement of fire early warning.
Disclosure of Invention
The invention aims to design a telemetering type calibration-free fire early characteristic gas detection device and a telemetering type calibration-free fire early characteristic gas detection method, so as to solve the problems that the existing gas-suction type fire early characteristic gas detection device is small in space detection range and the conventional telemetering type fire early characteristic gas detection device needs to be calibrated regularly.
The invention solves the technical problems through the following technical scheme:
a telemetric calibration-free early-fire signature gas detection apparatus, comprising: the device comprises a collimation focusing receiving-transmitting integrated optical component (1), an ARM embedded acquisition control analysis module (2), a DFB laser (3), a reference air chamber (5) and a single-mode optical fiber (6); two output ends of the ARM embedded acquisition control analysis module (2) are respectively connected with the collimation focusing receiving-transmitting integrated optical component (1) and the DFB laser (3); one end of the single-mode optical fiber (6) is connected with the collimation focusing receiving-transmitting integrated optical component (1), and the other end of the single-mode optical fiber is connected with the output end of the reference air chamber (5); the input end of the reference air chamber (5) is connected with the output end of the DFB laser (3), the laser receiving device (3) sends out detection light in a telemetering mode for detection, the collimation focusing receiving and transmitting integrated optical component (1) collimates laser detection signals sent by the DFB laser (3) and receives laser scattering echo signal light, and the reference air chamber (5) is filled with characteristic gas with standard concentration and used for carrying out online calibration on the concentration of the characteristic gas to be measured, which is measured in real time.
Light emitted by the DFB laser (3) enters a reference air chamber (5), then enters a collimation focusing receiving-transmitting integrated optical component (1) through a single-mode optical fiber (6), and emits detection light similar to parallel light to the outside after passing through the collimation focusing receiving-transmitting integrated optical component (1), the detection light is transmitted in a space light path, smoke generated by fire is reflected by reflectors such as a wall or the ground to form echo signal light, the echo signal light passes through the smoke again, is recovered by the collimation focusing receiving-transmitting integrated optical component (1), is sent into the ARM embedded acquisition control analysis module (2) for calculation processing, adopts the laser scattering echo signal to detect in a remote measuring mode, improves the space measuring range of the detecting device, and in addition, compared with the mode of adopting an angle reflector, the remote measurement is carried out in a scattered echo signal mode, the device is simple, and the device has better maneuverability and flexibility.
As a further improvement of the technical solution of the present invention, the collimating, focusing, transceiving integrated optical component (1) comprises: the device comprises a detection light collimator (11), a signal light receiving lens (12), a photoelectric detector (13), an indication laser (14) and a cylindrical shell (15); the detection light collimator (11) is arranged outside the cylindrical shell (15), and the optical axis of the detection light collimator (11) and the optical axis of the signal light receiving lens (12) are designed in an off-axis mode; the signal light receiving lens (12) is arranged at one end inside the cylindrical shell (15), the photoelectric detector (13) and the signal light receiving lens (12) are coaxially arranged, the photoelectric detector (13) is arranged at the focus of the signal light receiving lens (12) inside the cylindrical shell (15), and the electric signal input end of the photoelectric detector (13) is connected with the ARM embedded acquisition control analysis module (2); the indicating laser (14) is arranged at the top of the cylindrical shell (15); one end of the single-mode optical fiber (6) is connected with the input end of the detection light collimator (11).
As a further improvement of the technical scheme of the invention, the detection light collimator (11) comprises a detection light collimating lens (111) and an optical fiber interface (112), the detection light collimating lens (111) and the optical fiber interface (112) are coaxially arranged, and one end of the single-mode optical fiber (6) is connected into the optical fiber interface (112).
As a further improvement of the technical scheme of the invention, the reference air chamber (5) comprises: the optical fiber laser comprises two GRIN collimating lenses (51) and a reference gas chamber body (52), wherein the two GRIN collimating lenses (51) are respectively arranged at the input end and the output end of the reference gas chamber body (52), the input end of the reference gas chamber body (52) is connected with the output end of the DFB laser (3), and the output end of the reference gas chamber body (52) is connected with one end of a single-mode optical fiber (6).
As a further improvement of the technical scheme of the invention, the distance between the two GRIN collimating lenses (51) is 5cm, and the included angle between the end faces of the two GRIN collimating lenses (51) is 0.3 degree.
The utility model provides an be applied to remote measurement formula exempt from to calibrate gaseous detection device's of early characteristic of conflagration on-line demodulation method, ARM embedded collection control analysis module (2) send drive signal, the detection laser that drive DFB laser instrument (3) sent, DFB laser instrument (3) get into reference air chamber (5), send the echo signal light of surveying and receiving the scattering after collimation focusing receiving and dispatching integrative optical component (1) collimation, adopt the following formula real-time on-line demodulation by ARM embedded collection control analysis module (2) again and await measuring the concentration of characteristic gas:
in the formula, xL represents the integral concentration of the characteristic gas to be measured in the open measuring light path,
xrefLrefintegral concentration, S, of a characteristic gas representing a standard concentration in a reference gas chamber (5)2f/S1fExpressing a first harmonic to second harmonic normalized signal of the characteristic gas to be detected; s2f/S1frefThe first harmonic versus the second harmonic of the characteristic gas representing the standard concentration normalizes the signal.
The invention adopts the technical scheme that a first harmonic to a second harmonic normalized signal (S2f/S1f) is adopted to demodulate the gas concentration, the method eliminates the influence of the laser intensity, the response of a photoelectric detector and the change of a target reflection coefficient on a measurement result, and the gas concentration is demodulated on line in real time by directly inserting a reference gas chamber filled with gas to be measured with standard concentration into the device, thereby solving the problem that the instrument needs to be calibrated regularly, really achieving the long-term calibration-free effect of the instrument, and in addition, the method also has the advantages of no influence of a measurement environment, high measurement precision, high sensitivity, no need of additionally increasing a reference light path, simple structure and the like.
As a further improvement of the technical solution of the present invention, the collimating, focusing, transceiving integrated optical component (1) comprises: the device comprises a detection light collimator (11), a signal light receiving lens (12), a photoelectric detector (13), an indication laser (14) and a cylindrical shell (15); the detection light collimator (11) is arranged outside the cylindrical shell (15), and the optical axis of the detection light collimator (11) and the optical axis of the signal light receiving lens (12) are designed in an off-axis mode; the signal light receiving lens (12) is arranged at one end inside the cylindrical shell (15), the photoelectric detector (13) and the signal light receiving lens (12) are coaxially arranged, the photoelectric detector (13) is arranged at the focus of the signal light receiving lens (12) inside the cylindrical shell (15), and the electric signal input end of the photoelectric detector (13) is connected with the ARM embedded acquisition control analysis module (2); the indicating laser (14) is arranged at the top of the cylindrical shell (15); one end of the single-mode optical fiber (6) is connected with the input end of the detection light collimator (11).
As a further improvement of the technical scheme of the invention, the detection light collimator (11) comprises a detection light collimating lens (111) and an optical fiber interface (112), the detection light collimating lens (111) and the optical fiber interface (112) are coaxially arranged, and one end of the single-mode optical fiber (6) is connected into the optical fiber interface (112).
As a further improvement of the technical scheme of the invention, the reference air chamber (5) comprises: the optical fiber laser comprises two GRIN collimating lenses (51) and a reference gas chamber body (52), wherein the two GRIN collimating lenses (51) are respectively arranged at the input end and the output end of the reference gas chamber body (52), the input end of the reference gas chamber body (52) is connected with the output end of the DFB laser (3), and the output end of the reference gas chamber body (52) is connected with one end of a single-mode optical fiber (6).
As a further improvement of the technical scheme of the invention, the distance between the two GRIN collimating lenses (51) is 5cm, and the included angle between the end faces of the two GRIN collimating lenses (51) is 0.3 degree.
The invention has the advantages that:
(1) the DFB laser (3) of the technical scheme of the invention emits light to enter a reference air chamber (5), then the laser enters a collimation focusing receiving-transmitting integrated optical component (1) through a single mode fiber (6), the detection light which is approximate to parallel light is emitted to the outside after passing through the collimation focusing receiving-transmitting integrated optical component (1), the detection light is transmitted in a space light path, smoke generated by fire disaster is reflected by reflectors such as a wall body or the ground to form echo signal light, the echo signal light passes through the smoke again and is recycled by the collimation focusing receiving-transmitting integrated optical component (1) and is sent to an ARM embedded acquisition control analysis module (2) for calculation processing, the laser scattering echo signal is adopted for detection in a telemetering mode, the space measurement range of the detection device is improved, and in addition, compared with the adoption of an angle reflector mode, telemetering is carried out in a scattering echo signal mode, the device is simple and has better maneuverability and flexibility.
(2) The invention adopts the technical scheme that a first harmonic to a second harmonic normalized signal (S2f/S1f) is adopted to demodulate the gas concentration, the method eliminates the influence of the laser intensity, the response of a photoelectric detector and the change of a target reflection coefficient on a measurement result, and the gas concentration is demodulated on line in real time by directly inserting a reference gas chamber filled with gas to be measured with standard concentration into the device, thereby solving the problem that the instrument needs to be calibrated regularly, really achieving the long-term calibration-free effect of the instrument, and in addition, the method also has the advantages of no influence of a measurement environment, high measurement precision, high sensitivity, no need of additionally increasing a reference light path, simple structure and the like.
(3) The collimating focusing transceiving integrated optical component (1) in the technical scheme of the invention has the collimating optical axis strictly parallel to the receiving optical axis, so that scattered light signals scattered back by a diffuse reflection background are effectively received by the photoelectric detector (13).
(4) The surface of the signal light receiving lens (12) is plated with a 1500-channel 1600nm band-pass film, so that the light transmittance of the signal is further improved, the signal-to-noise ratio is further improved, and in addition, light in other bands can be filtered out to enter the photoelectric detector, and the photoelectric detector is prevented from being saturated.
Drawings
FIG. 1 is a block diagram of the operation of a telemetric calibration-free fire early stage characteristic gas detection apparatus according to an embodiment of the present invention;
FIG. 2 is a top view of a collimated focusing transmit-receive integrated optical component of an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The technical scheme of the invention is further described by combining the drawings and the specific embodiments in the specification:
as shown in fig. 1, an early fire multi-gas laser telemetry device includes: the device comprises a collimation focusing receiving-transmitting integrated optical component 1, an ARM embedded acquisition control analysis module 2, a DFB laser 3, a reference air chamber 5 and a single-mode optical fiber 6; two output ends of the ARM embedded acquisition control analysis module 2 are respectively connected with the collimating focusing receiving-transmitting integrated optical component 1 and the input end of the DFB laser 3; one end of the single-mode optical fiber 6 is connected with the collimation focusing receiving-transmitting integrated optical component 1, and the other end of the single-mode optical fiber is connected with the output end of the reference air chamber 5; the input end of the reference gas chamber 5 is connected with the output end of the DFB laser 3.
As shown in fig. 2, the collimating and focusing integrated optical transceiver component 1 includes: a detection light collimator 11, a signal light receiving lens 12, a photodetector 13, an indicator laser 14, and a cylindrical housing 15; the detection light collimator 11 is arranged outside the cylindrical shell 15, and an optical axis (collimation optical axis) of the detection light collimator 11 and an optical axis (receiving optical axis) of the signal light receiving lens 12 are designed in an off-axis mode, namely the collimation optical axis and the receiving optical axis are parallel but not coincident, so that the design mode is simple in structure, stable and reliable; the signal light receiving lens 12 is arranged at one end inside the cylindrical shell 15, the photoelectric detector 13 and the signal light receiving lens 12 are coaxially arranged on a receiving optical axis, the photoelectric detector 13 is arranged at the focus of the signal light receiving lens 12 inside the cylindrical shell 15, and the electric signal input end of the photoelectric detector 13 is connected with the ARM embedded acquisition control analysis module 2; the indicating laser 14 is arranged at the top of the cylindrical shell 15, and light emitted by the indicating laser 14 is in a visible light band (red or green laser), is parallel to light emitted by the detecting light collimator 11, and is used for indicating the emitting direction of light beams; one end of the single-mode optical fiber 6 is connected to the input end of the detection light collimator 11.
When the remote sensing detection is carried out on the fire early-stage characteristic gas based on the open light path, the design of the light path part can cause important influence on the overall detection performance, the collimation effect of the DFB laser 3 directly influences the detection distance and the intensity of the echo signal, and the parallelism of the optical axis of the collimation light path and the optical axis of the receiving light path can also directly influence the intensity of the echo signal detected by the system. The collimation optical axis of the collimation focusing receiving-transmitting integrated optical component 1 designed by the technical scheme is strictly parallel to the receiving optical axis, so that scattered light signals scattered back by a diffuse reflection background are effectively received by the photoelectric optical detector 13.
The model of the main control chip of the ARM embedded acquisition control analysis module is STM32F407ZGT6, and the ARM embedded acquisition control analysis module is used for: 1) generating a low frequency sawtooth wave signal (10Hz) and a high frequency sine wave signal (10KHz) for modulating the DFB laser 3; 2) the DFB laser 3 is accurately controlled in temperature by a PID algorithm, and the temperature control precision is +/-0.01 ℃; 3) the module is characterized in that signals received by the photoelectric detector 13 are collected, amplified, filtered and the like, secondary harmonic signals (2f) and primary harmonic signals (1f) are demodulated, the gas concentration is demodulated according to an embedded demodulation algorithm, the obtained gas concentration is displayed in real time, data are uploaded through RS-485, and the module further has the functions of gas concentration overrun acousto-optic alarm and the like.
As shown in fig. 2, the detection light collimator 11 includes a detection light collimating lens 111 and an optical fiber interface 112, the detection light collimating lens 111 and the optical fiber interface 112 are coaxially disposed, one end of the single-mode fiber 6 is connected to the optical fiber interface 112, and a distance from an end surface of the single-mode fiber 6 to the detection light collimating lens 111 can be finely adjusted.
The signal light receiving lens 12 and the detection light collimating lens 111 both adopt aspheric mirrors, compared with spherical mirrors, the design mode of the aspheric mirrors is simple in structure, the collimating and focusing effects are better, and the lens materials both adopt calcium fluoride materials (CaF)2) The light transmittance of the material in the near-infrared-mid-infrared band can reach more than 90%. The surface of the signal light receiving lens 12 is plated with a 1500-once 1600nm band-pass film, so that the signal light transmittance is further improved, the signal-to-noise ratio is further improved, in addition, light in other bands can be filtered out to enter the photoelectric detector, and the photoelectric detector is prevented from being saturated。
The reference gas chamber 5 comprises: the laser comprises two GRIN (fiber gradient index) collimating lenses 51 and a reference gas chamber body 52, wherein the two GRIN collimating lenses 51 are respectively arranged at the input end and the output end of the reference gas chamber body 52, the input end of the reference gas chamber body 52 is connected with the output end of the DFB laser 3, and the output end of the reference gas chamber body 52 is connected with one end of a single-mode fiber 6. The distance between the two GRIN collimating lenses 51 is 5cm, and a small angle of about 0.3 ° is kept between the end faces of the two GRIN collimating lenses 51 in order to avoid etalon noise caused by internal reflection at the end faces of the two GRIN collimating lenses 51 in the optical path.
The method for demodulating the calibration-free gas concentration by adopting the device comprises the following steps:
taking the fire characteristic trace gas CO demodulation as an example, when the sinusoidal modulation frequency ω of the current injected into the DFB laser 3 by the ARM embedded acquisition control analysis module 2 is 2 pi f, the instantaneous frequency v (t) of the emitted laser of the DFB laser 3 is:
wherein the content of the first and second substances,
the laser center frequency, a, frequency modulation amplitude, and t are time.
Considering the intensity modulation effect of current on laser, the output intensity I of the laser is very small due to the very small amplitude of the nonlinear modulation0(t) can be considered as a linear modulation, expressed as:
wherein the content of the first and second substances,
for laser at central frequency
Average intensity of (d), i1Is a linear intensity modulation degree (from
Normalized), ψ)1Is a linear modulation phase shift.
When the laser passes through the detected characteristic trace gas CO, the light intensity attenuation conforms to Lambert-beer law, and a (upsilon) L under the condition of small absorbance<0.05, the transmitted light intensity ItThe expression is simplified as follows:
wherein a (upsilon) (cm)-1) Is the absorption coefficient of the gas, L (cm) is the optical path length, aL is the absorbance, eta is the reflectivity of the actual target, P (atm) is the gas pressure, xCOIs the concentration of CO gas (mole fraction or volume fraction, commonly used volume fraction in ppm), SCO(atm-1·cm-2) And
respectively absorption line intensity and line type functions.
The gas absorption coefficient a (upsilon) (cm) in equation (3)-1) And performing Fourier series expansion on the laser instantaneous frequency v (t) as a function of the laser instantaneous frequency v (t) to obtain:
wherein the content of the first and second substances,
is the k-th order fourier expansion coefficient of the absorption coefficient.
The k-th harmonic component of equation (4) can be expressed as:
as can be seen from equation (5), the magnitudes of the fourier coefficients of the orders of the absorption coefficient a (v) are proportional to the product of the concentration of the gas and the optical path length.
An important problem in remote sensing of characteristic gas in early stage of fire based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) is that natural environment (such as natural objects like buildings, walls, ground or trees) is required to be used as a target, and the actual reflectivity of the target is unknown. To eliminate the effect of this factor on the measurement, one widely used method is the wavelength modulation technique and uses the first harmonic to normalize the second harmonic signal, called the "2 f/1 f" method. The individual harmonic signals of the modulation frequency can be separated from the original signal output by the detector by using a lock-in amplifier. To reduce the effect of the phase difference between the original signal and the reference signal on the amplitude measurement, the original signal is simultaneously demodulated using cos (k ω t) and sin (k ω t) to obtain the X and Y components of the k harmonic, respectively.
Second harmonic (S)2f) The amplitude of the signal can be expressed as:
wherein G is the response coefficient of the photodetector. Because the characteristic absorption peak of the gas is a symmetrical structure, the odd Fourier coefficient is 0 at the central frequency of the absorption peak. Therefore, equation (6) can be further simplified as:
for trace gas concentrations, there is 1>>Hk(k is 0,1, 2. cndot.) the first harmonic signal (S) can be obtained in the same manner as described above1f) The amplitude of (d) is:
by aSubharmonic signal (S)1f) Normalized second harmonic signal (S)2f) The following can be obtained:
from the formula (9), S2f/S1fThe signal has no relation with the light intensity, the response G of the photoelectric detector and the reflection system eta of the target, therefore, S is adopted2f/S1fThe signal is used for demodulating the gas concentration, so that the influence of the light intensity, the response of the photoelectric detector and the change of the reflection coefficient of the target on the measurement result can be eliminated. This feature is of great importance in the practical application of open optical paths for gas telemetry.
By using S2f/S1fWhen demodulating the gas concentration, there is also a very important practical problem of how to achieve calibration of the instrument. The traditional method is to put a series of gases to be measured with different standard concentrations into a measuring light path and measure S corresponding to different standard concentrations2f/S1fAnd obtaining the signal, and further obtaining an instrument calibration curve under the measurement condition. The method is time-consuming and labor-consuming, and the problem of inaccurate measurement can exist along with the use of the instrument, the calibration needs to be carried out periodically, and in addition, the actual use environment of the instrument is different from the calibration environment of a laboratory, and measurement errors can be introduced.
To overcome this problem, the device is inserted directly between the DFB laser and the probe light collimator by a length LrefAs shown in fig. 1, the reference gas cell is filled with a gas of a standard concentration. Let the concentration of standard CO gas in the reference gas chamber be xrefThen the obtained S is measured2f/S1fThe signals are:
in the formula, xrefLrefIs the integral concentration, x, of standard CO gas in the reference chamberCOL is the integral concentration of the measured CO gas in the open measuring light pathA may be considered a constant.
During instrument calibration, only laser beams emitted from the collimator are directly reflected to the photoelectric detector by using a target, and a reference measurement signal is obtained firstly, namely:
S2f/S1f,ref＝AxrefLref (11)
from equations (10) and (11), we can derive:
for example, when the reference gas chamber is filled with a CO standard gas with a concentration of 10000ppm, the integrated CO concentration of the reference gas chamber is 500ppm · m, and the integrated CO concentration measured in the open optical path is:
the method of directly inserting the reference air chamber into the device solves the problem that the instrument needs to be calibrated regularly, and really achieves the purpose that the instrument is free of calibration for a long time.
The device calibration-free design scheme is as follows: the calibration-free design scheme of the device is that a length L is directly inserted between a DFB laser and a detection light collimator of the devicerefThe gas to be measured (10000ppm of CO or 10000ppm of CO2 or 10000ppm of HCN) with standard concentration is filled in the reference gas chamber, the reference gas chamber is composed of a pair of fiber gradient index (GRIN) collimating lenses sealed in the gas chamber, and the distance between the two collimating lenses is 5 cm. To avoid etalon noise caused by reflections in the end faces of the two GRIN lenses in the optical path, a small angular cut (about 0.3 °) is maintained between the end faces of the two GRIN lenses.
The calibration-free gas concentration demodulation method comprises the following steps: normalizing the signal (S) with the first harmonic to the second harmonic2f/S1f) To adjust the gas concentration, the methodExcept the influence of the laser intensity, the response of the photoelectric detector and the change of the target reflection coefficient on the measurement result, the reference gas chamber filled with the gas to be measured with standard concentration is directly inserted into the device, and the formula is adopted
The method has the advantages of no influence of measurement environment, high measurement precision, high sensitivity, no need of additionally adding a reference light path, simple structure and the like.
The DFB laser 3 enters a reference gas chamber 5, gas to be detected with standard concentration (10000ppm of CO or 10000ppm of MC 2 or 10000ppm of HCN) is filled in the reference gas chamber 5, then laser enters a detection light collimator 11 through a single-mode optical fiber 6, detection light with approximate parallel light is emitted outwards after passing through the detection light collimator 11, the detection light is transmitted in a space optical path, smoke generated by fire disaster is formed, and then reflected by reflectors such as a wall body or the ground to form echo signal light, the echo signal light passes through the smoke again and is collected and focused on a photoelectric detector 13 by a signal light receiving lens 12, a band-pass film with 1500-1600nm wave band is plated on the surface of the signal light receiving lens 12, the influence of ambient stray light on a detection device is filtered, compared with the adoption of a band-pass filter, the method does not need to introduce a filter component, and the structure is more stable and compact. In addition, the device adopts the reference gas chamber 5 filled with the gas with standard concentration to be measured to demodulate the gas concentration measured in real time on line, thereby realizing the long-term calibration-free of the device and improving the precision and the reliability of the system measurement.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. Telemetering type calibration-free fire early characteristic gas detection device is characterized by comprising: the device comprises a collimation focusing receiving-transmitting integrated optical component (1), an ARM embedded acquisition control analysis module (2), a DFB laser (3), a reference air chamber (5) and a single-mode optical fiber (6); two output ends of the ARM embedded acquisition control analysis module (2) are respectively connected with the collimation focusing receiving-transmitting integrated optical component (1) and the DFB laser (3); one end of the single-mode optical fiber (6) is connected with the collimation focusing receiving-transmitting integrated optical component (1), and the other end of the single-mode optical fiber is connected with the output end of the reference air chamber (5); the input end of the reference air chamber (5) is connected with the output end of the DFB laser (3), the laser receiving device (3) sends out detection light in a telemetering mode for detection, the collimation focusing receiving and transmitting integrated optical component (1) collimates laser detection signals sent by the DFB laser (3) and receives laser scattering echo signal light, and the reference air chamber (5) is filled with characteristic gas with standard concentration and used for carrying out online calibration on the concentration of the characteristic gas to be measured, which is measured in real time.
2. The telemetric calibration-free early fire signature gas detection device of claim 1, wherein the collimated focusing transceiver optics (1) comprises: the device comprises a detection light collimator (11), a signal light receiving lens (12), a photoelectric detector (13), an indication laser (14) and a cylindrical shell (15); the detection light collimator (11) is arranged outside the cylindrical shell (15), and the optical axis of the detection light collimator (11) and the optical axis of the signal light receiving lens (12) are designed in an off-axis mode; the signal light receiving lens (12) is arranged at one end inside the cylindrical shell (15), the photoelectric detector (13) and the signal light receiving lens (12) are coaxially arranged, the photoelectric detector (13) is arranged at the focus of the signal light receiving lens (12) inside the cylindrical shell (15), and the electric signal input end of the photoelectric detector (13) is connected with the ARM embedded acquisition control analysis module (2); the indicating laser (14) is arranged at the top of the cylindrical shell (15); one end of the single-mode optical fiber (6) is connected with the input end of the detection light collimator (11).
3. The telemetric calibration-free early fire signature gas detection device according to claim 2, wherein the detection light collimator (11) comprises a detection light collimating lens (111) and a fiber interface (112), the detection light collimating lens (111) and the fiber interface (112) are coaxially arranged, and one end of the single-mode fiber (6) is connected to the fiber interface (112).
4. The telemetric calibration-free early fire signature gas detection device of claim 1, wherein the reference gas chamber (5) comprises: the optical fiber laser comprises two GRIN collimating lenses (51) and a reference gas chamber body (52), wherein the two GRIN collimating lenses (51) are respectively arranged at the input end and the output end of the reference gas chamber body (52), the input end of the reference gas chamber body (52) is connected with the output end of the DFB laser (3), and the output end of the reference gas chamber body (52) is connected with one end of a single-mode optical fiber (6).
5. The telemetric calibration-free early fire signature gas detection device of claim 4, wherein the distance between the two GRIN collimating lenses (51) is 5cm, and the included angle between the end faces of the two GRIN collimating lenses (51) is 0.3 degrees.
6. An online demodulation method applied to the telemetering calibration-free fire early-stage characteristic gas detection device as claimed in any one of claims 1-5, characterized in that an ARM embedded acquisition control analysis module (2) sends out a driving signal to drive a detection laser sent out by a DFB laser (3), the DFB laser (3) enters a reference gas chamber (5), and after being collimated by a collimating focusing transceiving integrated optical component (1), the DFB laser transmits, detects and receives scattered echo signal light, and then the ARM embedded acquisition control analysis module (2) demodulates the concentration of the characteristic gas to be detected in real time online by adopting the following formula:
in the formula, xL represents the integral concentration of the characteristic gas to be measured in the open measuring light path,
xrefLrefintegral concentration, S, of a characteristic gas representing a standard concentration in a reference gas chamber (5)2f/S1fExpressing a first harmonic to second harmonic normalized signal of the characteristic gas to be detected; s2f/S1frefThe first harmonic versus the second harmonic of the characteristic gas representing the standard concentration normalizes the signal.
7. The on-line demodulation method according to claim 6, wherein said collimated focusing transceiver-integrated optical assembly (1) comprises: the device comprises a detection light collimator (11), a signal light receiving lens (12), a photoelectric detector (13), an indication laser (14) and a cylindrical shell (15); the detection light collimator (11) is arranged outside the cylindrical shell (15), and the optical axis of the detection light collimator (11) and the optical axis of the signal light receiving lens (12) are designed in an off-axis mode; the signal light receiving lens (12) is arranged at one end inside the cylindrical shell (15), the photoelectric detector (13) and the signal light receiving lens (12) are coaxially arranged, the photoelectric detector (13) is arranged at the focus of the signal light receiving lens (12) inside the cylindrical shell (15), and the electric signal input end of the photoelectric detector (13) is connected with the ARM embedded acquisition control analysis module (2); the indicating laser (14) is arranged at the top of the cylindrical shell (15); one end of the single-mode optical fiber (6) is connected with the input end of the detection light collimator (11).
8. The on-line demodulation method according to claim 7, wherein the probe light collimator (11) comprises a probe light collimating lens (111) and an optical fiber interface (112), the probe light collimating lens (111) and the optical fiber interface (112) are both coaxially disposed, and one end of the single-mode optical fiber (6) is connected to the optical fiber interface (112).
9. The on-line demodulation method according to claim 6, characterized in that the reference gas cell (5) comprises: the optical fiber laser comprises two GRIN collimating lenses (51) and a reference gas chamber body (52), wherein the two GRIN collimating lenses (51) are respectively arranged at the input end and the output end of the reference gas chamber body (52), the input end of the reference gas chamber body (52) is connected with the output end of the DFB laser (3), and the output end of the reference gas chamber body (52) is connected with one end of a single-mode optical fiber (6).
10. The on-line demodulation method according to claim 9, wherein the distance between the two GRIN collimating lenses (51) is 5cm, and the included angle between the end faces of the two GRIN collimating lenses (51) is 0.3 degrees.
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