Qhov kub thiab txias transmitter yog ib qho khoom siv hluav taws xob siv dav hauv kev lag luam kev tswj hwm. Nws lub luag haujlwm tseem ceeb yog los hloov cov cim tsis muaj zog uas pom los ntawm qhov ntsuas kub (xws li thermocouples, thermal resistors RTDS lossis thermistors) rau hauv cov txheej txheem txheej txheem kev teeb tsa (feem ntau yog 4-20mA DC tam sim no cov cim lossis cov cim digital), thiab tom qab ntawd xa cov teeb liab no los tso saib cov cuab yeej, cov tswj, cov ntaub ntawv tau txais los yog cov khoom siv hluav taws xob ntawm qhov chaw nyob deb.
Lub hauv paus ntsiab lus ntawm kev ua haujlwm ntawm qhov kub thiab txias tuaj yeem ua tiav rau hauv cov kauj ruam tseem ceeb hauv qab no:
Temperature perception thiab raw signal generation:
Ib qho ntsuas kub (feem ntau yog ib qho thermocouple lossis thermal resistor xws li Pt100) los rau hauv kev sib cuag ncaj qha nrog qhov nruab nrab ntsuas kom paub txog nws qhov kub thiab txias.
Thermocouple (T/C): Raws li cov nyhuv Seebeck, thaum muaj qhov kub thiab txias sib txawv ntawm ob lub hlau sib txawv ntawm qhov ntsuas qhov kawg (kub kawg) thiab qhov kawg siv (txias kawg), qhov ntsuas kub muaj peev xwm (millivolt{0}} theem voltage teeb liab, mV) proportional rau qhov kub sib txawv yuav raug tsim nyob rau hauv Circuit Court.
Thermal resistance (RTD): xws li Pt100, raws li lub cev muaj zog uas tus nqi ntawm cov hlau conductor nce nrog nce kub (zoo kub coefficient). Qhov kub thiab txias hloov ua rau nws tus nqi tsis kam hloov (piv txwv li, nws yog 100Ω ntawm 0 degree).
Thermistors: Raws li cov yam ntxwv uas qhov kev tiv thaiv tus nqi ntawm cov khoom siv semiconductor hloov pauv nrog qhov kub thiab txias, lawv tau muab faib ua qhov tsis zoo kub coefficient (NTC) thiab zoo kub coefficient (PTC) hom.
Teeb pom kev zoo (cov kauj ruam tseem ceeb):
Amplification: Thawj lub teeb liab tsim los ntawm lub sensor (MV- theem voltage lossis tsis kam hloov) yog qhov tsis muaj zog heev. Cov hluav taws xob hluav taws xob hauv lub tshuab xa hluav taws xob ua ntej linearly amplifies nws mus rau qib txheem tsim nyog rau kev ua haujlwm tom ntej.
Txias kawg them nyiaj (rau cov thermocouples): Lub peev xwm ntawm lub tshuab hluav taws xob tsim los ntawm lub thermocouple yog ib qho kev ua haujlwm ntawm qhov kub thiab txias qhov sib txawv ntawm qhov kub kawg thiab qhov txias kawg (qhov kawg siv, feem ntau yog nyob rau hauv lub davhlau ya nyob twg ntawm lub transmitter). Txhawm rau kom tau txais qhov ntsuas kub zoo (kwv yees li 0 degree), lub tshuab xa hluav taws xob yuav tsum ntsuas qhov ntsuas kub ntawm nws lub davhlau ya nyob twg (qhov txias kawg), suav cov peev txheej thermoelectric uas yuav tsum tau them nyiaj raws li qhov ntsuas kub no, thiab superimpose (lossis cov txheej txheem sib npaug) nws mus rau qhov qub teeb liab, yog li tshem tawm qhov yuam kev los ntawm kev hloov pauv hauv qhov txias txias.
Linearization: Thermoelectric muaj peev xwm / tsis kam-kub kev sib raug zoo ntawm cov thermocouples thiab thermal resistors tsis yog ib txoj kab ncaj nraim tab sis muaj qee yam ntawm nonlinearity. Lub transmitter feem ntau khaws cov linearization nkhaus sib haum mus rau hom sensor sab hauv (los yog xam nws siv tus qauv). Lub teeb liab amplified/compensated yog linearized ncaj qha thiab linearly sawv cev rau qhov ntsuas kub tus nqi.
Tsawg-pass filtering: Nws tshem tawm siab- lub suab nrov zaus uas muaj nyob rau hauv lub teeb liab (xws li kev cuam tshuam hluav taws xob, kev cuam tshuam kev co, thiab lwm yam) los txhim kho qhov ruaj khov thiab qhov tseeb ntawm lub teeb liab.
Kev hloov dua siab tshiab
Hloov cov teeb liab analog (voltage) uas tau hloov kho (amplified, compensated, linearized, filtered) thiab precisely sawv cev rau qhov ntsuas kub rau hauv cov qauv tsim tawm teeb liab.
Cov teeb liab uas siv ntau tshaj plaws yog 4-20mA tam sim no teeb liab: lub teeb liab hloov pauv tam sim no ntws los ntawm lub voj. Zero kub lossis qis qis ntawm qhov ntau yam feem ntau sib haum rau 4mA, thiab qhov ntsuas kub tag nrho sib haum mus rau 20mA. Vim li cas 4-20mA?
4mA xoom offset: Nws tuaj yeem yooj yim paub qhov txawv ntawm cov teeb liab tsis zoo (4mA) los ntawm cov kab hluav taws xob cuam tshuam tsis raug (0mA).
Muaj zog tiv thaiv- cuam tshuam: Piv nrog cov cim hluav taws xob, cov teeb liab tam sim no tsis nkag siab rau cov kev hloov pauv hauv cov hlau tsis kam thiab qhov hluav taws xob poob thaum lub sij hawm ntev - kis tau tus mob thiab tsis tshua muaj kev cuam tshuam los ntawm cov suab nrov electromagnetic.
Ob -hlau fais fab mov: Ntau lub tshuab xa hluav taws xob txais yuav ob- xov hlau tsim, uas yog, lawv muab lub zog thiab xa cov teeb liab tam sim no ib txhij los ntawm ob lub xov hlau. Qhov tsawg kawg nkaus tus nqi ntawm 4mA ua kom lub transmitter tus kheej yam tsawg kawg nkaus kev khiav hauj lwm tam sim no yuav tsum tau (feem ntau hu ua "active zero point").
Teeb liab kis tau tus mob
Lub teeb liab hloov dua siab tshiab (xws li 4-20mA) raug xa mus rau qhov chaw taws teeb kawg ntawm cov xov hlau. Vim nws cov yam ntxwv zoo, tswj chav lossis PLCS thiab lwm yam khoom siv tau ncaj qha tau txais thiab ua cov teeb liab no rau:
Tso saib tus nqi kub (ntawm lub rooj vaj huam sib luag, DCS/SCADA tus neeg teb xov tooj chaw nres tsheb).
Nkag mus rau tus maub los (xws li PID maub los) rau kev ua haujlwm thiab kev tswj hwm.
Khaws rau hauv cov ntaub ntawv keeb kwm los yog siv rau kev txiav txim siab.
Tsav lub actuator (yog tias qhov kub thiab txias -raws li yuav tsum tau tswj).
