Yog tias koj puas tau rub lub "hmoov"siab transmittertawm ntawm kab, muab tso rau ntawm lub ntsuas ntsuas, thiab pom nws nyeem ib nrab ntawm ib feem ntawm xoom tsis muaj laj thawj, koj twb paub qhov kev ntxhov siab ntawm qhov teeb meem no: drift tsis tshua tshaj tawm nws tus kheej. Tsis muaj lub tswb rau "koj lub voj voog 4-20 mA maj mam dag rau koj." Cov txheej txheem tsuas yog pib khiav me ntsis nplua nuj, me ntsis lean, lossis tus tswj qib pib yos hav zoov, thiab tsis muaj leej twg xav tias yuav liam rau lub transmitter kom txog thaum peb lwm yam twb tau kuaj xyuas lawm.
Kab lus no taug kev los ntawm qhov tshwm sim tiag tiag hauv lub sensor thaum lub transmitter drifts, yog vim li cas nws tshwm sim txawm nyob rau hauv zoo -cov cuab yeej tu, thiab dab tsi cais lub transmitter uas tuav calibration rau xyoo los ntawm ib tug uas xav tau kev tu me nyuam.
Dab tsi "Drift" Tiag Tiag ntawm 4-20 mA Loop
Ua ntej nkag mus rau hauv qhov ua rau, nws tsim nyog ua kom meej txog dab tsi drift yog, vim tias qhov kho nyob ntawm seb hom twg koj tab tom cuam tshuam nrog.
Zero drifthloov tag nrho cov zis los ntawm ib tug taag offset. Yog hais tias ib tug transmitter yuav tsum xa 4 mA ntawm 0% thiab hloov xa 4.3 mA, qhov qub 0.3 mA offset tshwm sim ntawm txhua qhov taw tes ntawm qhov teev - 50% nyeem siab los ntawm tib cov paj raws li 0%. Qhov no feem ntau yog ib qho yooj yim rau pom thiab yooj yim kho nrog lub teb xoom trim.
Span driftyog qhov nyuaj siab dua. Qhov yuam kev loj hlob raws li qhov kev nyeem ntawv txav mus deb ntawm xoom, yog li lub transmitter tuaj yeem saib zoo kawg nkaus ntawm cov txheej txheem qis thiab tawm los ntawm ib feem pua lossis ntau dua nyob ze rau tag nrho. Qhov no yog qhov qhia tau hais tias "qhov ntsuas ntsuas tau nyeem zoo ntau hnub, tab sis ib yam dab tsi tawm thaum lub sijhawm ua haujlwm siab," thiab nws yog qhov ua yuam kev uas tau raug liam ntawm cov txheej txheem ua ntej leej twg kuaj xyuas lub ntsuas.
Feem ntau cov transmitters uas tsis ua hauj lwm qhia ib tug sib tov ntawm ob qho tib si, ntxiv rau ib co hysteresis, uas yog vim li cas ib tug tiag tiag calibration check - tsis yog ib tug nyob - nyeem ntawv sib piv rau lwm gauge - yog tib txoj kev txhim khu kev qha kom paub meej tias drift.
Qhov Tseeb Uas Qab Drift
Tsis muaj qhov no yog qhov tsis meej. Thaum ib lub tshuab xa tawm tawm ntawm lub rooj ntev zaum thiab mus rau hauv kev pabcuam, tib lub tes tsho ntawm yam - qhov kub thiab txias, kev caij tsheb kauj vab, av noo, kev vibration, thiab cov khoom qub qub - tus account rau yuav luag txhua qhov ntev - lub sij hawm poob [1]. Ntawm no yog li cas txhua tus yeej plays tawm.
Thermal Cycling ntawm Sensor Element
Txhua lub siab sensor muaj qhov kub thiab txias coefficient, txhais tau tias nws xoom thiab ncua kev hloov me ntsis nrog ambient lossis txheej txheem kub. Qhov ntawd tau them nyiaj rau hauv lub Hoobkas calibration, tab sis rov ua cua sov thiab cua txias dua - lub tank uas ntim nrog cov khoom kub thiab qhov khoob rau ambient, kev teeb tsa sab nraum zoov viav vias 40℃F nruab hnub thiab hmo ntuj - muab cov kev ntxhov siab tsis tu ncua ntawm lub diaphragm thiab nws cov kev sib txuas. Tshaj dhau cov voj voog txaus, cov nyiaj them ua haujlwm nkhaus lub Hoobkas ua hauv nres tsis sib xws nrog kev muaj tiag zoo li nws ib zaug ua.
Diaphragm qaug zog thiab khoom creep
Lub ntsiab lus nws tus kheej txav, txawm tias los ntawm microns. Nyias- diaphragm capacitive hlwb muaj qhov ua rau qeeb qeeb hauv lawv qhov chaw xoom tom qab xyoo ntawm kev sib tw siab, thiab cov ntsiab lus piezoresistive tsis tiv thaiv kab mob - cov qauv siv lead ua nws tus kheej hloov me ntsis hauv kev ntxhov siab. Ib daim duab uas nquag hais los ntawm cov ntaub ntawv tshawb fawb tso cai xoom drift rau capacitive sensors nyob rau hauv tas li muaj kev pab cuam nyob rau hauv qhov chaw ntawm ob peb puas mus rau ob peb feem kaum ntawm ib xyoo ib xyoo [2] - me me rau ntawm daim ntawv, tab sis txaus rau ib tug ceev ceev ceev - hloov los yog kev ruaj ntseg voj nyob rau hauv ob peb xyoos.
Electronic Component Aging
Nws tsis yog lub sensor xwb. Lub teeb liab txias hluav taws xob, A / D converter, siv hluav taws xob - tag nrho nws hnub nyoog. Capacitors qhuav tawm me ntsis, qhov tseem ceeb resistor nkag mus, thiab ntawm cov laus analog transmitters no ib leeg tuaj yeem suav rau qhov muaj txiaj ntsig ntawm tag nrho cov kev sib tw. Nws yog ib feem ntawm vim li cas ntse, microprocessor-raws li transmitters feem ntau tuav calibration noticeably zoo dua qub analog units nyob rau tib lub neej kev pab cuam - tsuas muaj tsawg analog circuitry sab laug mus drift.
Static Pressure Effects ntawm DP Transmitters
Qhov no catches ntau tus neeg los ntawm kev tiv thaiv. Ntawm qhov sib txawv ntawm qhov sib txawv ntawm qhov ntsuas qhov sib txawv me me hla ib kab khiav ntawm qhov siab zoo li qub (kab) siab, qhov yuam kev hauv qhov siab zoo li qub nws tus kheej txhais ua qhov yuam kev hauv DP nyeem - txawm tias qhov siab zoo li qub tsis yog qhov sib txawv uas koj ntsuas. High- DP daim ntawv thov zoo li qub, cov dej ntws ua ib qho piv txwv zoo sib xws, yog tus sawv cev tsis txaus ntseeg hauv cov lus tsis txaus siab vim qhov tseeb no.
Mechanical Installation Stress
Lub transmitter torqued nyuaj heev rau nws cov txheej txheem kev sib txuas, los yog mounted ntawm ib tug manifold uas yog me ntsis tawm ntawm qhov tseeb, yog nyob rau hauv load ua ntej nws puas pom cov txheej txheem siab. Qhov kev ntxhov siab hauv qab no tsis tas yuav tshwm sim rau hnub ib - nws tshwm sim li xoom hloov ob peb hlis tom qab ib zaug thermal cycling thiab vibration ua haujlwm nws xoob lossis txaj nws ntxiv. Kev vibration los ntawm cov twj nyob ze thiab compressors ua tib yam maj mam.
Kev rov ua dua dhau sijhawm - qhov "Ua" Tsis yog Qhov Ua rau tiag tiag
Tsim nyog naming cais: qee zaum tsis muaj qhov ua tsis tau zoo txhua. Lub transmitter tsuas yog laus nyob rau hauv txoj kab nrog nws luam tawm txhua xyoo kev ruaj ntseg specification, thiab lub calibration lub sij hawm tau stretched yav dhau los qhov ntsuas tau tsim los tuav. Ib qho kev tsis zoo xyuas qee qhov kev siv thev naus laus zis siv: ntau xyoo hauv kev pabcuam los ntawm kev tshaj tawm txhua xyoo kev ruaj ntseg spec - yog tias qhov ntsuas qhov yuam kev yog nyob rau hauv lub ballpark, nws yog kev laus qub, tsis yog qhov txhaum. Yog tias nws zoo tshaj qhov ntawd, lwm yam - thermal, mechanical, lossis zoo li qub siab - yog qhov ua txhaum ntau dua.
Ib qho piv txwv
Ib tug txheej txheem engineers ntawm ib nrab ntawm -sized batching cog ib zaug piav qhia chasing ib intermittent theem tswb rau qhov zoo dua ntawm ib lub hlis twg. DP-raws li theem transmitter ntawm lub tsho tsho reactor yuav nyeem kom raug ntawm kev kaw cov tshev, drift siab thaum lub sijhawm ua haujlwm, thiab rov kho dua ib hmos - uas ua rau nws zoo li cov txheej txheem teeb meem ntau dua li qhov teeb meem ntsuas. Nws tau rub cov ntaub ntawv calibration thiab hla - xa lawv tawm tsam batch kub cav kom pom cov qauv: lub transmitter qhov yuam kev tau taug qab yuav luag raws nraim nrog lub thermal cycling los ntawm lub tsho, tsis yog nrog rau qib nws tus kheej. Swapping nyob rau hauv ib tug transmitter nrog ib tug qis dua luam tawm kub coefficient - thiab ntxiv thermal rwb thaiv tsev ntawm impulse kab - daws nws yam tsis tau kov cov txheej txheem tswj txhua. Zaj lus qhia uas cuam tshuam nrog pab pawg tom qab: tsis txhob xav tias nyob - nyeem cov kev sib piv txwv tsis pub muaj kev sib tw, thiab tsis txhob xav tias qhov kev nyeem ntawv kaw ruaj khov txhais tau hais tias lub tshuab xa hluav taws xob zoo nyob rau hauv kev thauj khoom.
Diagnosting Drift Ua ntej Nws raug nqi koj
Ob peb tus cwj pwm ntes drift thaum ntxov, ua ntej nws hloov mus rau hauv cov txheej txheem chim siab lossis kev tshawb xyuas ua tsis tiav:
- Sib piv "raws li pom" vs. "raws li sab laug" tus lej ntawm txhua qhov ntsuas, tsis yog seb qhov kev nyeem ntawv kawg dhau lawm. Lub transmitter uas xav tau kev kho loj kom dhau yog qhia koj ib yam dab tsi, txawm tias nws dhau los.
- Ua pa rau huab cua thiab xyuas qhov tseeb xoom, tsis yog kev ua neej nyob sib piv rau lwm lub cuab yeej - ob lub twj tso kua mis tuaj yeem pom zoo rau ib leeg thiab ob qho tib si tsis raug.
- Taug qab trend, tsis yog dhau / poob.Lub tshuab xa hluav taws xob uas tau siv 80% ntawm nws qhov kev tso cai kam rau ntawm txhua daim tshev yog mus rau qhov chaw; ib tus tuav ruaj khov ntawm 5% ntawm kev ua siab ntev rau xyoo tej zaum tsis xav tau lub sijhawm luv dua.
- Sib cais re-xws li los ntawm qhov tseeb calibration.Hloov qhov qis / sab sauv qhov tseem ceeb ntawm lub tshuab xa hluav taws xob ntse hloov qhov nws qhia - nws tsis muaj dab tsi los kho qhov ntsuas qhov ntsuas. Qhov no tau sib xyaw ntau dua li qhov yuav tsum tau ua.
Calibration xyaum ua kom txo qis kev pheej hmoo drift
Siv Daim Ntawv Qhia Kom Zoo Traceable
Field calibration tsuas yog zoo li qhov nws tau muab piv rau. Tus qauv siv yuav tsum tau taug qab mus rau lub koom haum metrology hauv tebchaws - NIST hauv Asmeskas, lossis lub cev sib npaug ntawm lwm qhov - thiab raws li txoj cai ua haujlwm cov ntaub ntawv siv yuav tsum muaj lub ntsiab lus ntau dua li cov khoom xa tawm hauv kev sim, feem ntau hais txog yam tsawg kawg yog 3: 1 txog 4: 1 qhov tseeb piv, xa mus rau qhov ntsuas [3: AR] Calibrating lub transmitter ntsuas ntawm ± 0.075% tiv thaiv ib qho kev siv uas tsuas yog ob zaug raws li qhov tseeb tsis yog qhov tseeb tiag.
Teem caij nyoog los ntawm cov ntaub ntawv, Tsis Habit
Tsis muaj universal "yog" ncua sij hawm - nws nyob ntawm lub voj kev thuam, txheej txheem ib puag ncig, thiab txhua yam kev cai uas siv. Kev saib xyuas kev hloov pauv thiab kev nyab xeeb- cov cuab yeej ntsuas feem ntau muaj lawv tus kheej lub voj voog uas tsis muaj kev cuam tshuam txog kev sib tsoo [4]. Dab tsi tseem ceeb yog lub caij nyoog yog teem los ntawm cov ntaub ntawv keeb kwm calibration rau cov kev pabcuam tshwj xeeb, tsis tau theej los ntawm cov chaw tsim khoom cov lus pom zoo thiab yeej tsis rov mus xyuas dua.
Match Sensor Technology rau Daim Ntawv Thov
Tsis yog txhua qhov kev hnov tsw thev naus laus zis coj zoo ib yam hauv tib txoj kev ntxhov siab. Capacitive ntsiab yuav tuav xoom stability zoo nyob rau lub sij hawm; piezoresistive designs teb sai dua tab sis tuaj yeem pom ntau drift nyob rau hauv kev txhawb nqa; digital, microprocessor-compensated transmitters feem ntau outperform analog-tsuas yog tsim rau ntev-lub sij hawm ruaj khov vim hais tias qhov kub thiab txias them nyiaj yog suav nrog es tsis yog los ntawm aging analog Cheebtsam [5]. Rau siab - zoo li qub DP cov kev pabcuam, lub tshuab xa tawm nrog kev tshaj tawm, kuaj qhov ntsuas qhov ua yuam kev zoo li qub yog tsim nyog them rau - ntau cov ntaub ntawv faus tus lej no, thiab nws yog ib qho uas kwv yees tiag tiag - ntiaj teb kev ua haujlwm hauv daim ntawv thov ntawd.
Qhov no txhais li cas thaum koj tab tom teev ib lub transmitter
Rau tus neeg yuav khoom ntsuas cov khoom xa tawm ntau dua li qhov teeb meem ntawm qhov teeb tsa, qhov ua tau zoo yog los saib yav dhau los tus lej raug tus lej ntawm thawj kab ntawm cov ntaub ntawv. Cov specs uas tau twv ua ntej ntev - lub sij hawm drift cwj pwm zaum ntxiv: luam tawm txhua xyoo kev ruaj ntseg (feem ntau teev raws li % / xyoo), kub coefficient thoob plaws tag nrho cov nyiaj tau los, thiab - rau DP transmitters - qhov zoo li qub siab cov ntsiab lus. Lub transmitter nrog lub ntsiab lus qis dua qhov tseeb tab sis qhov kev ruaj ntseg nruj dua feem ntau yuav ua tau zoo dua "qhov tseeb dua" chav tsev ob lossis peb xyoos rau hauv kev pabcuam, uas yog qhov uas tus nqi tiag tiag ntawm drift tshwm sim: unplanned recalibration labor, process upsets, and in regulated applications, audit researchs.
Kev xav zaum kawg
Drift tsis yog lub cim qhia tias lub tshuab xa hluav taws xob tsis zoo - nws yog qhov tseeb ntawm lub cev rau ib qho sensor raug rau qhov tiag -lub ntiaj teb thermal cycling, mechanical stress, and component aging. Cov lus nug engineering tsis yog yuav ua li cas tshem tawm nws, tab sis yuav ua li cas qhia, teeb tsa, thiab ntsuas ib puag ncig nws kom nws nyob hauv ib qho kev kwv yees, cov ntaub ntawv sau tseg tsis yog tshwm sim raws li cov txheej txheem tsis meej txog rau lub hlis txij li tam sim no.
Cov ntaub ntawv
- ScienceDirect, "Pressure Transmitter Accuracy" -https://www.sciencedirect.com/science/article/abs/pii/S0019057809000329
- GAMICOS, "Pressure Transmitter Zero Drift: Diagnosis & Calibration Guide" -https://blog.gamicos.com/pressure-transmitter-zero-drift-diagnosis-calibration-cov lus qhia
- ISA, "Basics of Calibrating Pressure Transmitters," InTech -https://www.isa.org/intech-home/2016/september-october/departments/basics-ntawm-calibrating-siab-transmitters
- Tswj Ntiaj Teb, "Calibrating Pressure Instrumentation" -https://img.controlglobal.com/files/base/ebm/controlglobal/document/2022/08/1661881713031-ct1705calibratingpressureinstrumentation.pdf
- RealPars, "Dab tsi ua rau Analog Drift?" -https://www.realpars.com/blog/analog- drift
