Piav qhov emissivity ntawm infrared thermometers
Emissivity yog qhov piv ntawm lub zog hluav taws xob ntawm ib qho khoom tiag tiag rau ntawm lub cev dub ntawm qhov kub thiab txias nyob rau tib lub sijhawm. Cov xwm txheej zoo ib yam yog hais txog tib lub geometric tej yam kev mob (emission radiation area, solid angle size and direction for Measuring radiation power) thiab spectral conditions (spectral range for Measuring radiation flux). Vim muaj kev sib raug zoo ntawm emissivity thiab ntsuas, muaj ntau lub ntsiab lus ntawm emissivity.
Hemisphere emissivity yog qhov sib piv ntawm lub zog hluav taws xob hluav taws xob (emissivity) tawm los ntawm lub tshuab hluav taws xob hauv ib cheeb tsam hauv cheeb tsam mus rau qhov chaw hemisphere mus rau emissivity ntawm lub cev dub ntawm tib qhov kub. Nws muab faib ua ob hom: tag nrho emissivity thiab spectral emissivity.
Ib txwm emissivity
Ib txwm emissivity yog cov emissivity ntsuas nyob rau hauv ib tug me me lub kaum sab xis nyob rau hauv ib txwm kev taw qhia ntawm ib tug radiating nto. Nws yog qhov piv ntawm radiance nyob rau hauv ib txwm kev coj mus rau lub radiance ntawm ib tug blackbody nyob rau tib lub kub. Vim lub fact tias infrared systems ntes hluav taws xob hluav taws xob nyob rau hauv ib tug me me lub kaum ntse ntse nyob rau hauv ib txwm kev taw qhia ntawm lub hom phiaj nto, ib txwm emissivity yog tseem ceeb heev.
Rau blackbodies, tag nrho cov emissivity qhov tseem ceeb yog sib npaug rau 1, thaum rau cov khoom tiag, tag nrho cov emissivity qhov tseem ceeb yog tsawg dua 1. Qhov emissivity peb tam sim no xa mus yog qhov nruab nrab emissivity.
Hais txog emissivity kho:
Qhov emissivity ntawm cov khoom sib txawv ntawm qhov sib txawv, thiab txhawm rau ua kom qhov tseeb ntawm qhov ntsuas kub, feem ntau yuav tsum tau kho emissivity. Vim lub fact tias tus pas ntsuas kub yog calibrated nrog ib tug blackbody, lub emissivity ntawm tej yam khoom nto yog me dua li ntawm ib tug blackbody.
Cov txheej txheem ntawm emissivity calibration rau infrared tus pas ntsuas kub yog los kho qhov amplification yam ntawm lub amplifier raws li emissivity ntawm cov khoom sib txawv, thiaj li hais tias lub teeb liab generated los ntawm hluav taws xob ntawm ib tug tiag tiag cov khoom nrog ib tug tej yam kub nyob rau hauv lub system yog tib yam li lub teeb liab. generated los ntawm ib tug blackbody nrog tib kub. Piv txwv li, yog tias qhov emissivity ntawm ib yam khoom yog {{0}}.8, lub amplification yam ntawm lub amplifier yuav tsum tau nce mus rau 1/0.8=1.25 npaug ntawm qhov qub. Txawm li cas los xij, nyob rau hauv cov chaw lag luam, feem ntau nyuaj rau kev txiav txim siab lub hom phiaj emissivity tsis tau vim muaj cov khoom sib txawv, cov duab, thiab qhov chaw ntawm lub hom phiaj ntsuas. Kev ntsuas yuam kev los ntawm lwm yam tuaj yeem ua rau muaj qhov sib txawv ntawm qhov ntsuas qhov ntsuas thiab qhov tseeb. Kev taw qhia txog kev hloov pauv emissivity tuaj yeem daws qhov teeb meem no zoo yam tsis muaj kev cuam tshuam rau kev ntsuas linearity. Raws li kev ntsuas kub los yog txheej txheem kub, kho raws li cov kauj ruam hauv qab no:
Piv txwv li, qhov ntau ntawm tus pas ntsuas kub yog 500-1400 degree
Qhov tseeb kub yog 1200 degree, thiab ntsuas kub yog 1150 degree,
Hauv qhov no, emissivity parameter tuaj yeem hloov kho rau:
(1150-500) ÷ (1200-500)=0.928 ≈ 0.93
