CN201210140Y - Multi-parameter laser wavelength modulation spectrum detection apparatus used in fire field - Google Patents

Abstract

A fire scene multi-parameter laser wavelength modulation spectrum detection device, including a laser, a multi-channel laser controller, a white cell, a photodetector, a lock-in amplifier module, a multi-channel data acquisition card, and a microcomputer, is characterized in that: There are multiple lasers, and each laser is externally connected to a multi-channel laser controller to control its working current and temperature. The outgoing laser light of the laser is respectively connected to the multiplexer through the optical fiber, and the output optical fiber of the multiplexer is connected to the input of the White pool. There is an optical fiber collimator indirectly at the optical port, a flue gas pretreatment device is installed at the inlet of the White cell, and an air pump is installed at the gas outlet; a photodetector is installed at the light outlet of the White cell, and the output of the photodetector is The signal is divided into two roads and connected to two lock-in amplifier modules, and the output signals of the two lock-in amplifier modules are sent to the microcomputer through a multi-channel data acquisition card; the multi-channel laser controller and the lock-in amplifier module and the multi-channel Signal lines are connected between the data acquisition cards to realize signal transmission.

Description

Fire scene multi-parameter laser wavelength modulation spectrum detection device

Technical field:

The utility model belongs to the technical field of fire monitoring, in particular to a laser absorption gas analysis and detection device.

Background technique:

The multi-parameters of the fire scene include the oxygen concentration of the fire scene, the concentration of various toxic gases and the smoke concentration, which are important factors affecting the escape and rescue of people in a fire. Among the gas analysis and detection methods, the common detection methods at present mainly include the following: the electrochemical method using electrodes and electrolytes to detect gas; the electrical method using semiconductor gas device detection; using the refractive index or Optical methods for detecting gases by using properties such as light absorption. These methods have their own fields of application, but limited by the detection mechanism, the electrochemical and electrical methods have defects such as short sensor life, easy "poisoning", serious cross-interference, and long response time, which cannot meet the multi-parameter detection requirements of the fire scene. Simultaneous detection of components and strong gas selectivity. Existing detection equipment based on optical methods has the advantages of high sensitivity and strong gas selectivity, but there are still the following defects in practical use:

①Fourier Transform Infrared Spectroscopy (FTIR) can measure and analyze gas concentration in a wide infrared band. Although this method has high sensitivity and can realize simultaneous analysis and measurement of multiple toxic gases, it needs to use spectroscopic elements and scanning methods , and gas sampling is required, gas measurement and analysis can only be carried out in the laboratory, and online real-time measurement of gas products at the fire scene cannot be realized.

② The optical path of the existing optical gas detection equipment is relatively fragile, easily affected by environmental interference, and it is more difficult to monitor the smoke concentration at the same time.

③ Existing gas detection devices are difficult to achieve real-time online detection of multi-component gases.

Utility model content:

The purpose of this utility model is to provide a high-sensitivity fire multi-parameter laser wavelength modulation spectrum detection device capable of simultaneous on-line detection of multi-parameters in the fire field, so as to overcome the above-mentioned defects in the prior art and realize multi-component gas in fire smoke Online real-time detection provides scientific reference for fire rescue work.

The technical solution of the utility model is:

A fire scene multi-parameter laser wavelength modulation spectrum detection device, including a laser, a multi-channel laser controller, a white cell, a photodetector, a lock-in amplifier module, a multi-channel data acquisition card, and a microcomputer, is characterized in that: There are multiple lasers, and each laser is externally connected to a multi-channel laser controller to control its working current and temperature. The outgoing laser light of the laser is respectively connected to the multiplexer through the optical fiber, and the output optical fiber of the multiplexer is connected to the input of the White pool. There is an optical fiber collimator indirectly at the optical port, a flue gas pretreatment device is installed at the inlet of the White cell, and an air pump is installed at the gas outlet; a photodetector is installed at the light outlet of the White cell, and the output of the photodetector is The signal is divided into two roads and connected to two lock-in amplifier modules, and the output signals of the two lock-in amplifier modules are sent to the microcomputer through a multi-channel data acquisition card; the multi-channel laser controller and the lock-in amplifier module and the multi-channel Signal lines are connected between the data acquisition cards to realize signal transmission.

The fire field multi-parameter laser wavelength modulation spectrum detection device is characterized in that there are four lasers, DFB semiconductor lasers are used, and their central wavelengths correspond to the absorption lines of CO ₂ , CO, HCN and O ₂ respectively; The photodetector is an InGaAs photodiode as the receiving device, and its spectral response range is 900-1700nm.

The utility model adopts a multi-channel laser controller, multiple lasers, a wave combiner, an optical fiber collimator, a white pool, a photoelectric detector, two phase-locked amplification modules, and a multi-channel data Acquisition card, a microcomputer, flue gas pretreatment device, air extraction pump and white pool inlet and outlet pipelines constitute a laser wavelength modulation spectrum fire scene multi-parameter detection device.

In the utility model, the multi-channel laser controller mainly realizes the following functions: (1) generate low-frequency sawtooth scanning current with adjustable amplitude and frequency to realize laser wavelength scanning; (2) generate sinusoidal modulation current to realize laser wavelength modulation, and provide The base frequency (f) reference signal and the frequency multiplier (2f) reference signal are sent to the lock-in amplifier module; (3) control the working temperature of each laser; (4) control the working timing of multiple laser detection channels to realize time-division multiplexing of multiple lasers It can be used and provide time-sharing timing synchronization signals to multiple data acquisition cards. The multiple lasers used in the utility model have their central wavelengths respectively corresponding to the absorption lines of the gas to be detected in the multi-parameters of the fire scene; the lasers adopt DFB semiconductor lasers, and their outstanding advantages are that the wavelength tuning speed is very fast and the output spectral line is very narrow (<50MHz ), good monochromaticity. The multiplexer combines the laser output from the four lasers with a bundle of optical fibers to output sequentially, and sends them into the White Pool after being collimated by the fiber collimator installed at the front end of the White Pool's optical path.

The measurement principle of the fire smoke of the utility model:

According to the Lambert-Beer law, when a beam of input parallel light with light intensity I ₀ is incident on the gas to be measured, the light passes through the gas and attenuates, and the output light intensity I(t) is different from the input light intensity I ₀ (t) and the gas The relationship between the concentrations is

I(t)=I ₀ (t)exp[-α(v)CL] (1)

Where α(v) is the gas absorption coefficient, that is, the absorption line shape of the gas at a certain frequency v; L is the length of the absorption path; C is the concentration of the gas to be measured.

The system adds a slowly changing sawtooth wave periodic sweep current and a sinusoidal modulation current with a small amplitude to the DC drive current of the semiconductor laser, and the frequency and output light intensity of the light source are also modulated accordingly:

v＝v ₀ +v _m sin ωt (2)

I ₀ (t)＝I ₀ [1+η sin ωt] (3)

In the formula, v ₀ is the center frequency of the light source without modulation; v _m is the modulation amplitude of the frequency; η is the light intensity modulation coefficient; ω=2πf, f is the current modulation frequency. Substituting (2) and (3) into (1), then:

I(t)＝I ₀ (1+η sin ωt)exp[-α(v ₀ +v _m sin ωt)CL] (4)

In the near-infrared band, the gas absorption coefficient is very small, satisfying α(v)CL<<1, and the modulation amplitude of the light source is also small, that is, η<<1, so the formula (4) can be approximated as:

I(t)＝I ₀ [1+η sin ωt-α(v ₀ +v _m sin ωt)CL] (5)

Since the experiment is carried out at atmospheric pressure, the absorption line type can be described by the Lorentz line type:

$\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{\mathrm{<span\; class="notranslate">\; \&delta;\; v</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

where α ₀ represents the absorption coefficient of pure gas at the center of the absorption line; v _g and δv correspond to the center frequency of absorption and the half-width of the absorption line, respectively. Therefore, when the central wavelength of the light source output is precisely locked on the gas absorption peak, that is, v ₀ =v _g , formula (6) is substituted into formula (5), and expanded into a Fourier series sequence to obtain the fundamental frequency component and the second harmonic The coefficients of the wave components are:

I _f ＝I ₀ η I _2f ＝-kα ₀ CLI ₀ (7)

In the formula,

$\begin{array}{cc}\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>}{{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}& \mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; \&delta;\; v</span>}\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

So there are:

$\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; f</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&eta;</span>}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; CL</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

It can be seen that the ratio of the second harmonic to the first harmonic does not contain the I ₀ item, so using it as the output of the system can eliminate the interference caused by factors such as light source fluctuations. In formula (9), except for the gas concentration C to be measured, other parameters are constant, and the system output is proportional to the gas concentration. Through standard gas calibration, the concentration of the gas to be measured can be obtained.

When the laser propagates in the White cell, in addition to being absorbed by the gas to be measured, it is also subject to the absorption or scattering of the smoke particles or the combined (extinction) effect of the two. The radiation energy received by the photoelectric receiver that normally receives parallel light Flux will be weakened. According to the national standard GB4715, the utility model measures the dimming coefficient to represent the smog concentration, and the dimming coefficient is represented by the following formula:

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 10</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

代替

代入(10)式可以获得减光系数，以表征烟雾浓度。In the formula, m is the extinction coefficient in dB/m; d is the optical measurement length of the test smoke; P ₀ is the received radiation power when there is no smoke; P is the received radiation power when there is smoke. According to the calculation result of formula (7), measure the fundamental frequency component I _f received when there is smoke and the fundamental frequency component I _f0 received when there is no smoke, and use

replace

Substituting into (10) formula can obtain the extinction coefficient to characterize the smoke concentration.

After research, it is found that the gas components in the multi-parameters of the fire scene have a weak attenuation of the laser light intensity, which can be ignored compared to the light intensity attenuation caused by the fire smoke, and has little effect on the measurement of the dimming coefficient; and the fire smoke will not produce high The frequency component affects the detection of the concentration of gas components. Therefore, the device can simultaneously detect multiple gas components and fire smoke without cross interference.

The central wavelengths of the 4 DFB semiconductor lasers used in the utility model correspond to the absorption lines of _O2 and other 3 gases to be detected respectively. In the implementation, the detection of different gases can be realized only by replacing lasers with different wavelengths, which has a good performance Gas selectivity.

Because the utility model adopts 4 DFB semiconductor lasers, its wavelength tuning speed is fast, and the output spectrum line is very narrow, and the output wavelength can be tuned accurately on the absorption peak of the gas to be measured, and the interference between components can be effectively eliminated; The laser controller drives 4 lasers according to the time-division multiplexing method, which can realize the simultaneous detection of 4 gas components; adopts the appropriate algorithm and data processing method, and uses the system optical path to measure the extinction coefficient of the smoke, and realizes the fire scene. Real-time simultaneous detection of parameters. The utility model can fundamentally solve the defects of the traditional detection method, has the advantages of real-time, multi-component, high sensitivity, strong gas selectivity, high reliability, strong anti-environmental interference ability, etc., and is suitable for various environmental places Multi-parameter online detection of the fire scene.

Popularization and application of the utility model will promote the development of fire detection technology in my country, and realize real-time on-line monitoring of multi-parameters in the fire field.

Description of drawings:

Accompanying drawing 1 is the schematic diagram of the system composition of the multi-parameter laser wavelength modulation spectrum detection device for the fire scene of the present invention.

Accompanying drawing 2 is the structural diagram of multi-channel laser controller.

Accompanying drawing 3 is the schematic diagram of White cell multiple reflection principle.

Accompanying drawing 4 is the flow chart of real-time data analysis processing of the present utility model.

Detailed ways:

Example 1

The fire field multi-parameter laser wavelength modulation spectrum detection device of this embodiment consists of a multi-channel laser controller 1, 4 DFB lasers 12, a multiplexer 2, an optical fiber collimator 3, a white cell 4, and a One photoelectric detector 5, two lock-in amplification modules 6, one multi-channel data acquisition card 7, one microcomputer 8, flue gas pretreatment device 9, air pump 10, inlet and outlet pipelines 11, etc. The flue gas pretreatment device 9 sends the flue gas at the monitoring site into the inlet of the White Pool 4, and the gas outlet at the other end is connected to the suction pump 10; the optical fiber collimator 3 is installed at the entrance of the optical path of the White Pool, and the photodetector 5 It is installed at the exit of the optical path of White Pool, and its output signal is divided into two paths, and is sent into two lock-in amplifier modules 6 simultaneously; Connect with the analog input port of the data acquisition card.

In order to improve the sensitivity of photodetection, a white cell is used to increase the optical path length. White pool 4 used in the present embodiment utilizes spherical reflector imaging principle to make, and White pool 4 is mainly made up of a primary mirror and two secondary mirrors, and the curvature radius of primary mirror and secondary mirror is consistent, and between primary mirror and secondary mirror The distance between the centers and the radius of curvature are equal, so that a confocal cavity is formed between the primary and secondary mirrors, and the beam is reflected back and forth between the primary and secondary mirrors. The principle diagram of multiple reflections of the White cell is shown in Figure 3.

In this embodiment, four DFB lasers are used, the center wavelengths are 1609.0nm, 1567.133nm, 1537.965nm and 1273.0nm respectively, corresponding to the absorption lines of CO ₂ , CO, HCN and O ₂ respectively; the multi-channel laser controllers are multiplexed by time division The working mode drives 4 DFB lasers 12, performs wavelength scanning and wavelength modulation to it, and is responsible for: (1) providing the time-sharing timing synchronization signal 13 of wavelength scanning to the multi-channel data acquisition card 7 to ensure the synchronization of data acquisition, (2 ) provides the sinusoidal wavelength modulated base frequency f and frequency multiplied 2f reference signal 14 to the lock-in amplification module 6 . The multiplexer combines the lasers output by the 4 lasers 12 into one beam, which is transmitted by optical fiber, and sent into the White pool after being collimated by the fiber collimator 3 installed at the front end of the 4 optical paths of the White pool. The photodetector 5 uses an InGaAs photodiode as a receiving device, and its spectral response range is 900-1700nm.

When working, the flue gas at the monitoring site is processed by the flue gas pretreatment device 9, and then sucked into the white pool 4 by the air pump 10 through the air inlet; 2 and the fiber collimator 3 are sent into the White cell, and the laser light is emitted to the photodetector 5 after multiple reflections and absorption attenuation in the White cell 4, and then converted into an electrical signal by the photodetector 5, and sent in two ways Enter two lock-in amplifier modules 6 to carry out frequency selective amplification, obtain the fundamental frequency (f) component and the second harmonic (2f) component, then carry out A/D conversion by the multi-channel data acquisition card 7, the digital quantity after conversion Send to the microcomputer 8 to carry out real-time data analysis and processing. When performing data analysis and processing, referring to formula (9), it is only necessary to calibrate the concentration of the gas to be measured in advance to obtain the concentration-I _2f /I _f curves of the four gases to be measured, and substitute the data collected by the data acquisition card 7 into the calibration A variety of gas concentrations to be measured can be obtained from the curve; referring to the formula (10), it is only necessary to collect the fundamental frequency component when there is no smoke in advance, and substitute the smoke fundamental frequency component collected by the data acquisition card 7 into the formula (10). Obtains the extinction coefficient that characterizes the smoke concentration. Therefore, the multi-parameter information of the fire scene including the oxygen concentration of the fire scene, the concentration of various toxic gases and the smoke concentration is obtained at the same time.

Claims (2)

1, a kind of scene of a fire many reference amounts optical maser wavelength modulated spectrum pick-up unit, include laser instrument, the multi-path laser controller, the White pond, photodetector, phase-locked amplification module, the multi-channel data acquisition card, microcomputer is characterized in that: described laser instrument has many, and all external multi-path laser controller of each laser instrument is to control its working current and temperature, the shoot laser of described laser instrument inserts wave multiplexer respectively by optical fiber, be connected to optical fiber collimator between the light inlet in the output optical fibre of wave multiplexer and White pond, the air intake opening in White pond is equipped with Flue Gas Pretreatment Device, and the gas outlet is equipped with aspiration pump; The light-emitting window place in described White pond is equipped with photodetector, and the output signal of photodetector is divided into two the road and inserts two phase-locked amplification modules, and the output signal of two phase-locked amplification modules is delivered to microcomputer through the multi-channel data acquisition card; Be connected with signal wire between described multi-path laser controller and phase-locked amplification module and the multi-channel data acquisition card and realize the signal transmission.

2, the scene of a fire according to claim 1 many reference amounts optical maser wavelength modulated spectrum pick-up unit is characterized in that described laser instrument has four, adopts the dfb semiconductor laser instrument, and its centre wavelength is corresponding CO respectively ₂, CO, HCN and O ₂The absorption line; Described photodetector is for selecting for use the InGaAs photodiode as receiving device, and its spectral response range is 900～1700nm.

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