气体分析仪的原理与应用Servomax

1、ParamagneticPhotometricZirconia仕富梅气体分析技术Paramagnetic仕富梅磁氧技术ParamagneticO2O2O2O2O2O2O2O2O2O2O2O2O2O2O2O2COCOCO2 CO2 SO2 HCl HCl N2 NO NO N2 O2O2COCOCO2 CO2 SO2 SO2 HCl N2 NO2 NO2 NO2 O2O2O2COCOCO2 CO2 SO2 SO2 HCl N2 氧气是唯一对磁场具有很强吸引力的气体,我们称它为“顺磁性” LED 光源 光电池接收器Servomex Paramagnetic CellParamagnetic磁条充满

2、氮气的球反馈线圈悬浮的镜子Paramagnetic使用一对充满氮气的哑铃来检测氧气哑铃悬浮在一个很强的、不均匀的磁场中Paramagnetic在校验期间，通入氮气使哑铃保持静止位置，从而建立分析仪的零点Paramagnetic样气中的氧气在磁场的作用下，使哑铃发生偏转，由光学反馈系统检测O2O2O2O2O2O2Paramagnetic电流反馈回反馈线圈，产生一个反方向的力距该力距使悬浮回到零位电流正比于氧气的浓度氧气测量原理氧气测量原理 样气中的氧气总是设法使得哑铃样气中的氧气总是设法使得哑铃偏转偏转 高精度的反馈回路阻碍哑铃的旋高精度的反馈回路阻碍哑铃的旋转转,给出氧浓度的直接测量值给出氧浓

3、度的直接测量值 Paramagnetic仕富梅磁氧技术仕富梅磁氧技术: 高可靠性高可靠性 高稳定性高稳定性 长寿命长寿命 高精确度高精确度 不受环境气体的影响不受环境气体的影响仕富梅磁氧技术用于 .xendos 1800/1900. and is supplied as OEM modules to Medical equipment manufacturers.x xentraentra 41004100 xentra 49001100 A/HPortablesParamagnetic氧分析的原理 电化学式 顺磁性氧的顺磁性 Unpaired electrons align with a m

4、agnetic field and behave like small magnets Oxygen molecules are attracted into a magnetic field NB - Thermal agitation knocks electrons out of alignment and reduces magnetic susceptibility磁氧传感器的类型 Magneto-dynamic (Servomex) 热/磁风 Quinke cell磁风薄的玻璃管气体出口细的铂丝气体入口环形流动室冷态的氧分子受到磁场的吸引磁风测量室的特点 热装置容易受到背景气体的导

5、热系数影响 Temperature sensitive Tilt and flow sensitive Pressure sensitive (effect = 1:1.5) Combustibles may burn on filament causing errors 普通的灵敏度Quinke cellQuinke cell features Constant flow of nitrogen reference gas required Poor sample pressure sensitivity - effect of changes = 2:1 Suitable for very

6、 corrosive gases Not affected by sample thermal conductivityServomex paramagnetic cellServomex null balance systemMagneto-dynamic cell Null balance system - extremely linear Fast response, low pressure effect (1:1) Very high resolution Temperature compensated Corrosion resistant materials Not sensit

7、ive to thermal conductivity of background gases Extremely long life - does not fail “unsafe”Servomex cell features Effect of background gases small Operates up to 110C (with 1100H) Effect of pressure (1:1) is easily compensated Solvent resistant version available (364N cell) Flammable samples can be

8、 handled (ia) electronicsInfraredG f xInfraredG f x Soft UVTransmissionWavelength Each gas absorbs energy in the electromagnetic spectrum in a unique way - its finger print.Servomex Photometric TechnologiesFinger prints are used to identify and analysespecific components in a sample.InfraredG f xTra

9、nsmissionWavelength Each gas absorbs energy in the electromagnetic spectrum in a unique way - its finger print.Servomex Photometric TechnologiesFinger prints are used to identify and analysespecific components in a sample.InfraredG f x Soft UVInfraredSO2CO2CO58152.0TransmissionWavelength (microns)Se

10、rvomex SBDW InfraredFor the reference filter, an absorptionband in an area of the spectrum wherethere is no absorption is selected.For the measurement filter, an absorption band corresponding to the required gas is selected.InfraredServomex Infrared cell(Single Beam, Dual Wavelength - SBDW) Filter w

11、heelIR Source2 - 15 micron( Broad band, hot wire filament)ChopperMotorLensSample cellPyroelectricDetectorLensInfraredWhen the reference filter is in the beam, there is noabsorption by the target gas in the sample.This gives a zero reading.Servomex SBDW InfraredRInfraredWhen the measuring filter is i

12、n the beam, energy is absorbed by the target gas in the sample.This gives the span reading.The difference between the zero and span signals is p r o p o r t i o n a l t o t h e concentration in the sample.Servomex SBDW InfraredInfraredRMDual Beam IR Sensors Drift results from Measurement cell contam

13、ination. Ageing detector, mechanical movementSensitiveMicrophonicDiaphramRefrence CellMeasurementCellInOutRotatingFilterWheelIRSourceCO FilledDetectorG f xServomex Gfx(Gas Filter Correlation) Filter wheelwith gas filled cellsIR Source2 - 15 micron( Broad band, hot wire filament)ChopperMotorLensSampl

14、e cellPyroelectricDetectorLensG f xServomex Gas Filter Correlation (Gfx)Some gases - including CO, CO2 , NO and SO2 - have a spectrum with a fine structure.This allows its use as a specific and highly selective optical filter.3.558152.5TransmissionWavelength fine gas structureG f xWhen the cell fill

15、ed with reference gas (nitrogen) is in the beam, there is some absorption by the target gas in the sample.This is used as a zero reading.RG f xServomex Gfx(Gas Filter Correlation) When the cell filled with the target gas is in the beam, energy is absorbed by the target gas in the sample.This gives t

16、he span reading.The difference between the zero and span signals is proportional to the concentration in the sample.RMG f xServomex Gfx(Gas Filter Correlation) Gas Filter CorrelationHow It Works Uses a gas filter to produce a beam which has already selectively absorbed IR energy absorbed by the gas

17、to be measured, referenced to a beam which has not.Infrared Absorption Like many other pollutant gases, CO absorbs electromagnetic radiation in the infrared spectrum. The amount of energy absorbed provides a measurement of the CO concentration.IR WavelengthAbsorption4.7 umCO AbsorbanceInfrared CO Se

18、nsors We can use an infrared filter to select only those wavelengths close to 4.7 um.IR SourceLensFilterSample CellDectorInfrared CO Sensors For high concentration CO measurements, sensors using filters to select the 4.7 um region are ideal. For low concentration CO measurements dual beam sensors ar

19、e often used. These measurements are subject to two limitations.Cross Sensitivity Other gases also absorb at 4.7 um resulting in cross sensitivity errors.H2OCO2CO4.7 umWaveLengthAbsorptionWavelengths transmittedby filter.Gas Filter Correlation. Overcomes both of these problems giving High sensitivit

20、y for low level CO measurement. Stable, low interference from back ground gases.IR Spectrum Fine Structure The Infrared spectrum of CO is not a smooth curve.Wave LengthAbsorption4.7 umLow ResolutionAbsorption spectrumIR Spectrum Fine Structure The Infrared spectrum of CO is not a smooth curve but co

21、nsists of a number of distinct lines.Wave LengthAbsorption4.7 umHigh ResolutionDetailBeam spectrum after NO gas filter5060708090 5 5.1 5.2 5.3 5.4 5.5 5.6 Transmittance / MicrometersOverlay Y-Zoom CURSORFile # 1 : NO_302 16/02/96 17:24 Res=.2 cm-1200mb NO filled by LI cellIR Spectrum Fine Structure

22、We can use filters filled with CO to selectively remove only those wavelengths directly associated with CO. This is called Gas Filter CorrelationGfx Sensor Construction Stable infrared source emits a collimated beam of broad band infrared energy.WavelengthIntensityGfx Sensor Construction Bandpass fi

23、lter isolates the region of the IR spectrum of interest for CO.WavelengthIntensity4.7 umGfx Sensor Construction Gas filled cells ( Cuvettes ) containing CO and N2 rotate alternately into the IR beam.WavelengthIntensity4.7 umCO filled cuvetteN2 filled cuvetteGfx Sensor Construction When N2 cuvette is

24、 in the beam all of the IR energy is transmittedWavelength( expanded )Intensity4.7 umCO filled cuvetteN2 filled cuvetteGfx Sensor Construction When CO cuvette is in the beam then the IR energy is removed only at the wavelengths absorbed by CO.Wavelength( expanded )Intensity4.7 umCO filled cuvetteN2

25、filled cuvetteIndividual absorptionlinesGfx Sensor Construction The alternating beam passes down the sample cell, through the gas being measured and onto the detector.InOutSample Cell filledwith gas measuredSolid statedetectorDetectedsignalN2CON2COGfx Sensor Construction The difference in the signal

26、 level when the two cuvettes are in the IR beam represents only the energy at those wavelengths absorbed by CO.InOutDetectedsignalN2CON2COGfx Sensor Construction The signals for the two cuvettes are balanced electrically so that when there is no CO in the sample gas the two levels are the same.InOut

27、DetectedsignalN2CON2CON2CON2COGfx Sensor Measurements When the sample contains no CO then the signals are balanced with no difference. The measured CO concentration will be zero.N2CON2CONo CO ingas sample.Gfx Sensor Measurements When the sample contains CO then the signal with the N2 cuvette is redu

28、ced while the signal with the CO cuvette is virtually unchanged. The difference between the signals gives the CO concentration in the sample gas.N2CON2CONo CO ingas sample.N2CON2CODeltaCO in thegas sampleGfx Sensor Measurements When the sample contains another gas like CO2 then the signal with both

29、cuvettes is reduced equally. The difference in the signals is zero The measured CO concentration in the sample gas will be zero.N2CON2CONo CO ingas sample.N2CON2CODeltaCO in thegas sampleN2CON2COCO2 in thegas sampleGfx Sensor Measurements When the sample cell is contaminated or the source intensity

30、changes then the signal with both cuvettes is reduced equally. The difference in the signals is still zero The measured CO concentration in the sample gas will be zero.N2CON2CONo CO ingas sample.N2CON2CODeltaCO in thegas sampleN2CON2COCell contaminatedNO, IR filter and water vapour spectra0204060801

31、00 5 5.1 5.2 5.3 5.4 5.5 5.6 Transmittance / MicrometersOverlay Y-Zoom CURSORFile # 1 : NO_302 16/02/96 17:24 Res=.2 cm-1200mb NO filled by LI cellPrinciple of operation Soft UV* Soft UV is low energy ultra violet radiation greater than 250 nmServomex Soft Ultra Violet cellFilter wheelUV Source 250-

32、900 nm ( Broad band, hot wire filament)ChopperMotorLensSample cellSilicon PhotodiodeDetectorLens Soft UVTransmission400500600250Wavelength (nm)Servomex Soft UVFor the reference filter, an absorptionband in an area of the spectrum wherethere is no absorption is selected. Soft UVFor the measurement fi

33、lter, an absorption band corresponding to the target gas is selected. ChlorineWhen the reference filter is in the beam, there is noabsorption by the target gas in the sample.This gives a zero reading.Servomex Soft UV Soft UVRWhen the measuring filter is in the beam, energy is absorbed by the target gas in the sample.This gives the span reading.The difference between the zero and span signals is proportional to target gas in the sample.Servomex Soft UV Soft UVRMServomex Photometric Technologies: Reliable Stable Immune to obscuration Vibration resistant Solid state detector Gfx optio