Temperature Compensation ofNovelNDIRCO2GasSensor

Astheconsumption offossil fuel isincreased, theair pollution andemission ofcarbon dioxide isgetting more severe thaneverbefore. Themainreason ofairpollution comesfromtheautomotives (refrigerant gases, CO,CO2 NOx)andindustrial plants. Theactive waysofdecreasing pollutants aretoproduce ultra lowemission vehicle, energy efficient hybrid vehicle inautomotive areaandtousehighenergy efficient products withlowemission ofpollutants in industrial areas andinhomeappliances. Amongtheair pollution gases, thecarbon dioxide causestheglobal warming, sothere isagreat effort todecrease CO2emission inorder toalleviate theGreenhouse effect. Furthermore, the central HVAC (Heat, ventilation, andAirConditioning) system controls theventilation andtemperature ofnew buildings indowntown area, sothere areaccumulations of hazardous gases including carbon dioxide. Therefore, the quality ofair intheconfined areaisgetting important factor. Sincetheindoor airquality (IAQ)isrelevant for humanwellness, adequate ventilation isimportant toprevent serious health problems liketheSickHouseSyndrome (SHS)andNew Building Syndrome (NBS). Inadequate ventilation inhouse andoffice accumulates carbon dioxide inliving roomandworking areasoitcauses somefatigue symptoms whentheconcentration ofCO2isover5,000 ppm. Koreangovernment recently legitimates the installation ofenergy saving heatexchanger system inorder todecrease energyconsumption andtoprevent theair pollution related illness. TheEU reinforced toinstall CO2 gassensor module inthermal radiator that usesfossil fuel. Therefore, there areneeds ofmonitoring airquality torun HVAC systemattheoptimum condition, sothere is potential needtouseaffordable gassensor formonitoring air quality. Currently, there aretwomethods formonitoring CO2 concentration; oneistouseNonDispersive Infra Red (NDIR) sensor, andtheother istoapply solid electrolyte sensor [1]. Eventhough thesolid electrolyte typeismore affordable than that ofNDIR,theNDIRgassensor hasmore technical advantages likes long-term stability, high accuracy, andlowpowerconsumption. Furthermore, since NDIRtype usestheoptical sensing principle, ithasahigher selectivity intheopen-air conditions. However, NDIRgassensor uses generally thermopile detector that areusedfornon-contact temperature detection, sothetemperature compensation of NDIRgassensor isessential forengineering application and commercial products. Inthis paper, wearegoing topropose arevised novel optical cavity structure forNDIR gassensor withtwo concavemirrors andpresented thesimulation and experimental results ofthenewlydesigned sensorfor monitoring CO2concentration. Fortheapplications inhome andautomotive HVAC systems, wetried tofigure outthe temperature compensation methodanddescribed the experimental results.