A kind of infrared gas analyzer
Technical field
The utility model relates to a kind of infrared gas analyzer.
Background technology
Because the vibration of majority of gas molecule and rotation spectrum is all at infrared band, when the vibration rotation feature frequency of the frequency of incident infrared radiation and molecule was identical, infrared radiation will be absorbed by gas molecule, causes the decay of radiation intensity.Infrared gas analyzer is exactly to utilize the principle that this gas molecule absorbs infrared radiation and make; has the measuring accuracy height; speed fast and can METHOD FOR CONTINUOUS DETERMINATION etc. characteristics; be widely used in the quality restriction of fields such as petrochemical complex, metallurgy, machining, pharmacy, biochemistry, environmental protection, quality monitoring, cement and auto industry (engine performance monitoring system), high-purity gas, also can be applied to the laboratory gas analysis.Existing most of infrared gas analyzers all adopt the infra-red heat light source, and luminescence efficiency is poor, and introduce problem such as heat interference easily; Infrared detection chamber relatively simple for structure easily is acted upon by temperature changes; The anti-vibration ability of traditional thin-film electro capacity sensor, and have the defective of frequency response characteristic difference; These factors have all influenced the precision of whole measurement, the accuracy and the reliability of data to a great extent.
Summary of the invention
The technical problems to be solved in the utility model is to provide a kind of infrared gas analyzer, adopts the higher infrared light supply of efficient, the infrared detection chamber of more reasonable structure, and the sensor that performance is more excellent with the frequency response characteristic of enhanced system, improves the accuracy of measuring.
The technical scheme that its technical matters that solves the utility model adopts is: a kind of infrared gas analyzer, it is made up of LED infrared light supply, light path chopper, sample air chamber, optical filter, interference gas filter chamber, infrared detection chamber, sensor, signal condition platelet, mainboard and man-machine interface, sensing chamber and back sensing chamber before described infrared detection chamber comprises, described sensor is connected between preceding sensing chamber and the back sensing chamber; The back sensing chamber of described infrared detection chamber has scalable lengthening air chamber, is the extension that is communicated with back sensing chamber.
Wherein, be provided with the humidity calibration sheet between described back sensing chamber and the extension.
Wherein, described wave filter comprises that charging into the interference gas filter chamber and the series connection that can absorb the gas that disturbs the wavelength infrared light places this interference gas filter chamber optical filter afterwards.
Wherein, described sensor adopts microbridge type air mass flow sensor or the monocrystalline silicon piezoresistance differential pressure pick-up that declines.
Wherein, described infrared light supply adopts the LED cold light source.
The beneficial effects of the utility model are:
1) the utility model has adopted space structure to consider the sensing chamber of design from the aerodynamics angle, sensing chamber and back sensing chamber before this sensing chamber comprises, then sensing chamber is made up of the principal part and the extension that are communicated with again, on the one hand, the flow that tested gas before making like this in sensing chamber and the back sensing chamber produces after absorbing infrared light is more even, have frequency response characteristic preferably, and then improved the accuracy of sensor measurement; On the other hand, a temperature correction sheet can be set between principal part and extension, can arrive the appropriate location to remove humidity effect, further guarantee the accuracy of sensor measurement by adjusting the temperature correction sheet.
2) since at present the nickel nobelium mercerising source poor heat stability that adopts usually of infrared gas analyzer, the life-span is short, measuring error is big, the utility model adopts the LED cold light source to replace nickel nobelium mercerising source as infrared light supply, be serviceable life 3000-25000 hour, the reliability height, luminescence efficiency is the three-to-four-fold of traditional hot light source, has solved the problem of hot interference admirably.
3) existing infrared gas analyzer adopts the thin-film capacitor microphone as sensor usually, has the Frequency Response difference and to shaking responsive shortcoming, and the utility model replaces with microbridge type air mass flow sensor with the thin-film capacitor microphone, this sensor utilizes heat transfer theory, realize the linear transformation of the MAF of surveying and output voltage signal, and adopt the encapsulation of ISO technology, have very high reliability, repeatability and stable.Stopped the influence of vibrations from the sensor aspect like this, avoided the traditional sensors problem, the problem includes: the gas leakage problem to measuring.
Description of drawings
The utility model is described in further detail below in conjunction with drawings and Examples, in the accompanying drawing:
The structural representation of the infrared gas analyzer that Fig. 1 provides for the utility model embodiment.
Embodiment
Usually, the measuring principle of infrared gas analyzer is based upon a kind of gas and can only absorbs on the ultrared characteristic of its characteristic wavelength section basis, promptly be based on most of asymmetric gas molecules certain wavelength in the infrared ray wave band is had absorption function, and its degree of absorption is relevant with the concentration of tested gas.Can absorb the Infrared of 4.5-5 mum wavelength, CH as CO
4Can absorb 2.3 μ m, 3.4 μ m, 7.6 μ m infrared rays.
In the present embodiment, the structure of infrared gas analyzer comprises sensor 6, infrared light supply 1 and chopper 2, sample air chamber 3, wave filter 4, sensing chamber 5 after series connection is placed on infrared light supply on the infrared light path direction of propagation as shown in Figure 1; Wherein, the shell wall at sample air chamber 3 two ends is provided with air intake opening 3-1 and gas outlet 3-2, and tested gas enters, flows out from gas outlet 3-2 from air intake opening 3-1 with certain flow rate; Wave filter 4 comprises filtering air chamber 4-1 and filter plate 4-2, charge among the filtering air chamber 4-1 to absorb the gas that disturbs the wavelength infrared light, and filter plate 4-2 is the logical type of arrowband band, in order to not use the wavelength part in the filtering infrared light; Be full of tested gas in the sensing chamber 5,5-1 of sensing chamber and the back 5-2 of sensing chamber before comprising, the back 5-2 of sensing chamber is communicated with extension 7 again; Sensor 6 is connected between preceding 5-1 of sensing chamber and the back 5-2 of sensing chamber.
For improving accuracy, the enhancing anti-seismic performance of measuring, in the present embodiment, infrared light supply 1 adopts the LED cold light source, and sensor 5 adopts microbridge type air mass flow sensors.
Above-mentioned infrared gas analyzer is when work, and infrared light supply 1 sends the wide range infrared light and enter sample air chamber 3 behind the pulsed light that is modulated into certain frequency by chopper 2; Tested gas charges into sample air chamber 3 with certain flow rate from air intake opening 3-1, absorbs by discharging from gas outlet 3-2 after the subband in the infrared light in the sample air chamber 3; The infrared light of subband after by tested gas absorption is by wave filter 4 afterwards, disturb the wavelength part in the gas absorption infrared light that charges among the filtering air chamber 4-1, filter plate 4-2 selects the specialized narrowband wave band that disturbs in the absorbed infrared light of wavelength, other wave band of usefulness not of filtering; At last, infrared light enters the detecting device 5 that is full of tested gas, through the difference in flow that the asymmetric absorption of front and back sensing chamber produces, sensor 5 is caught this difference in flow signal, comes discriminatory analysis to go out the concentration that measures object component in the tested gas according to this difference in flow signal in subsequent process.Infrared light is in entering sensing chamber 5 time, tested gas in the preceding sensing chamber can absorb the part wavelength of infrared light and expand, tested gas in the back sensing chamber can further absorb infrared light and expand, thereby between preceding sensing chamber and back sensing chamber, can produce difference in flow, because the design of back sensing chamber has the extension, make that this flow is more even, so the measurement of sensor 6 is more accurate.
With the SO2 analyser is example, and interference component has CH
4, H
2O, CO
2, then charge into CH among the filtering air chamber 4-1
4, CO
2Gas can all absorb the absorbent spectral line of these gases in the spectrum of infrared light supply 1, so enter the intensity variations and the CH of sensing chamber's 5 mid-infrared lights
4, CO
2Interference irrelevant, like this, CH
4, CO
2Interference obtained compensation by filtering air chamber (4-1), CO simultaneously
2Can absorb unnecessary heat transfer; Optical filter 4-2 allows 6.5 um ~ 9um(SO
2The characteristic absorption wave band) infrared light enter sensing chamber, be limited to SO seeing through light
2In the absorption region; In addition, between back 5-2 of sensing chamber and the extension 7 a humidity calibration sheet (not drawing among the figure) can be set, can arrive the appropriate location to remove humidity effect, so the signal that sensor 6 captures is the purified signal that will expect after multiple interfering component removal or the compensation to obtain by the adjustment corrector strip at any time.
Above embodiment is only unrestricted in order to the explanation the technical solution of the utility model, only with reference to preferred embodiment the utility model is had been described in detail.Those of ordinary skill in the art should be appreciated that and can make amendment or be equal to replacement the technical solution of the utility model, and do not break away from the spirit and scope of technical solutions of the utility model, all should be encompassed in the middle of the claim scope of the present utility model.