Ngiyo ngingo yambere mubice bibiri bigize urukurikirane. Iyi ngingo izabanza kuganira ku mateka n'ibibazo byo gushushanyaubushyuhe bushingiye ku bushyuhesisitemu yo gupima, kimwe no kugereranya na sisitemu yo gupima ubushyuhe bwa termometero (RTD). Bizasobanura kandi guhitamo thermistor, iboneza ry'ubucuruzi, hamwe n'akamaro ka sigma-delta analog-to-digitale (ADCs) muri kariya gace gakoreshwa. Ingingo ya kabiri izasobanura uburyo bwo guhitamo no gusuzuma sisitemu yanyuma yo gupima.
Nkuko byasobanuwe mu kiganiro cyabanjirije iki, Optimizing RTD Temperature Sensor Sisitemu, RTD ni résistoriste irwanya ubukana. Thermistors ikora kimwe na RTD. Bitandukanye na RTDs, ifite gusa coefficente yubushyuhe bwiza, thermistor irashobora kugira coefficient nziza cyangwa mbi. Coefficient yubushyuhe bubi (NTC) igabanya ubukana bwayo uko ubushyuhe buzamuka, mugihe ubushyuhe bwiza bwubushyuhe (PTC) bwongera ubushyuhe bwabyo uko ubushyuhe buzamuka. Ku mutini. 1 yerekana ibisubizo biranga bisanzwe bya NTC na PTC thermistors kandi ubigereranya nu murongo wa RTD.
Kubijyanye nubushyuhe bwubushyuhe, umurongo wa RTD uri hafi kumurongo, kandi sensor ikubiyemo ubushyuhe bwagutse cyane kuruta ubushyuhe (mubisanzwe -200 ° C kugeza + 850 ° C) kubera imiterere idafite umurongo (exponential) ya thermistor. Ubusanzwe RTD itangwa muburyo buzwi buzwi busanzwe, mugihe imirongo ya thermistor itandukana nababikora. Tuzabiganiraho muburyo burambuye mugice cyo gutoranya thermistor igice cyiyi ngingo.
Thermistors ikozwe mubikoresho byinshi, mubisanzwe ceramika, polymers, cyangwa semiconductor (mubisanzwe oxyde de metal) hamwe nicyuma cyiza (platine, nikel, cyangwa umuringa). Thermistors irashobora kumenya ihinduka ryubushyuhe bwihuse kuruta RTDs, itanga ibitekerezo byihuse. Kubwibyo, thermistors ikoreshwa cyane na sensor mubisabwa bisaba igiciro gito, ingano ntoya, igisubizo cyihuse, ibyiyumvo byimbitse, hamwe nubushyuhe buke, nko kugenzura ibikoresho bya elegitoroniki, kugenzura inzu no kubaka inyubako, laboratoire yubumenyi, cyangwa indishyi zikonje zikoreshwa mubucuruzi. cyangwa inganda zikoreshwa. intego. Porogaramu.
Mubihe byinshi, thermistors ya NTC ikoreshwa mugupima ubushyuhe nyabwo, ntabwo PTC thermistors. Amashanyarazi amwe ya PTC arahari arashobora gukoreshwa mumuzunguruko urenze urugero cyangwa nkibishobora kwimurwa kubisabwa umutekano. Kurwanya-ubushyuhe bwumurongo wa PTC thermistor yerekana akarere gato cyane ka NTC mbere yo kugera aho bahindura (cyangwa point ya Curie), hejuru aho imyigaragambyo izamuka cyane nuburyo bwinshi bwubunini buri hagati ya dogere selisiyusi. Mugihe gikabije, thermistor ya PTC izabyara ubushyuhe bukabije mugihe ubushyuhe bwo guhinduranya burenze, kandi guhangana kwayo kuzamuka cyane, bizagabanya ibyinjira muri sisitemu, bityo birinde kwangirika. Ahantu ho guhinduranya ubushyuhe bwa PTC mubusanzwe buri hagati ya 60 ° C na 120 ° C kandi ntibikwiriye kugenzura ibipimo by'ubushyuhe muburyo butandukanye bwa porogaramu. Iyi ngingo yibanze kuri thermistors ya NTC, ishobora gupima cyangwa kugenzura ubushyuhe buri hagati ya -80 ° C na + 150 ° C. Ubushyuhe bwa NTC bufite ibipimo byo guhangana kuva kuri oms nkeya kugeza kuri 10 MΩ kuri 25 ° C. Nkuko bigaragara ku gishushanyo. 1, ihinduka ryokurwanya kuri dogere selisiyusi ya thermistors iragaragara cyane kuruta kurwanya termometero. Ugereranije na thermistors, ibyiyumvo bikabije bya thermistor hamwe nagaciro gakomeye ko kwihanganira byorohereza uruzinduko rwarwo, kubera ko thermistors idasaba iboneza ryihariye ryihariye, nka 3-wire cyangwa 4-wire, kugirango yishyure imbaraga zo kurwanya. Igishushanyo cya thermistor gikoresha gusa ibyoroshye 2-wire.
Ibipimo by'ubushyuhe buke bushingiye ku bipimo by'ubushyuhe bisaba gutunganya ibimenyetso neza, kugereranya-kuri-digitale, guhuza umurongo, n'indishyi, nkuko bigaragara ku gishushanyo. 2.
Nubwo urunigi rwibimenyetso rusa nkurworoshye, haribintu byinshi bigoye bigira ingaruka kubunini, igiciro, n'imikorere yibibaho byose. ADI isobanutse neza ya ADC portfolio ikubiyemo ibisubizo byinshi byahujwe, nka AD7124-4 / AD7124-8, bitanga inyungu nyinshi muburyo bwa sisitemu yubushyuhe kuko ibyinshi mubyubaka bikenewe mubisabwa byubatswe. Ariko, hariho ingorane zitandukanye mugushushanya no gutezimbere ubushyuhe bwo gupima ubushyuhe bwa termistor.
Iyi ngingo iraganira kuri buri kibazo kandi itanga ibyifuzo byo kubikemura no kurushaho koroshya uburyo bwo gushushanya sisitemu.
Hariho ubwoko butandukanye bwaNTC thermistorsku isoko uyumunsi, guhitamo rero thermistor ibereye kubyo usaba birashobora kuba umurimo utoroshye. Menya ko thermistors yashyizwe ku rutonde rwizina ryabo, aribwo barwanya izina kuri 25 ° C. Kubwibyo, 10 kΩ thermistor ifite nominal irwanya 10 kΩ kuri 25 ° C. Thermistors ifite nominal cyangwa shingiro yo kurwanya indangagaciro kuva kuri ohm nkeya kugeza 10 MΩ. Thermistors ifite ibipimo bike byo kurwanya (nominal resistance ya 10 kΩ cyangwa munsi yayo) mubisanzwe ishyigikira ubushyuhe buke, nka -50 ° C kugeza + 70 ° C. Thermistors ifite amanota menshi yo guhangana irashobora kwihanganira ubushyuhe bugera kuri 300 ° C.
Ikintu cya thermistor gikozwe mubyuma bya oxyde. Thermistors iraboneka mumupira, radiyo na SMD. Amashara ya Thermistor ni epoxy yatwikiriwe cyangwa ikirahuri gikingiwe kugirango hongerweho uburinzi. Epoxy itwikiriye umupira wa termistoriste, radiyo hamwe nubushyuhe bwo hejuru bikwiranye nubushyuhe bugera kuri 150 ° C. Ibirahuri by'ibirahuri bikwiranye no gupima ubushyuhe bwinshi. Ubwoko bwose bwo gutwikira / gupakira nabyo birinda ruswa. Thermistors zimwe na zimwe zizaba zifite amazu yinyongera kugirango yongererwe kurinda ahantu habi. Amashanyarazi yamashanyarazi afite igihe cyo gusubiza byihuse kuruta radiyo / SMD. Ariko, ntibiramba. Kubwibyo, ubwoko bwa thermistor bwakoreshejwe biterwa nimpera yanyuma nibidukikije aho thermistor iherereye. Iterambere rirerire rya thermistor riterwa nibikoresho byayo, gupakira, hamwe nigishushanyo. Kurugero, ubushyuhe bwa epoxy-NTC thermistor irashobora guhindura 0.2 ° C kumwaka, mugihe thermistor ifunze ihindura 0.02 ° C kumwaka.
Thermistors iza muburyo butandukanye. Ubushuhe busanzwe busanzwe bufite 0.5 ° C kugeza 1.5 ° C. Igipimo cyo kurwanya thermistor nigiciro cya beta (igipimo cya 25 ° C na 50 ° C / 85 ° C) gifite kwihanganira. Menya ko beta agaciro ka thermistor itandukana nuwabikoze. Kurugero, 10 kΩ NTC thermistors kuva mubakora bitandukanye bazagira beta zitandukanye. Kuri sisitemu zuzuye, thermistors nka Omega series 44xxx ikurikirana irashobora gukoreshwa. Bafite ubunyangamugayo bwa 0.1 ° C cyangwa 0.2 ° C hejuru yubushyuhe bwa 0 ° C kugeza 70 ° C. Kubwibyo, urwego rwubushyuhe rushobora gupimwa hamwe nukuri gusabwa hejuru yubushyuhe bugena niba thermistors ikwiranye niyi porogaramu. Nyamuneka menya ko uko ukuri kwa Omega 44xxx ari ukuri, nigiciro cyinshi.
Guhindura kurwanya kuri dogere selisiyusi, agaciro ka beta gakoreshwa. Agaciro ka beta kagenwa no kumenya ubushyuhe bubiri hamwe nuburwanya bujyanye na buri bushyuhe.
RT1 = Kurwanya ubushyuhe 1 RT2 = Kurwanya ubushyuhe 2 T1 = Ubushyuhe 1 (K) T2 = Ubushyuhe 2 (K)
Umukoresha akoresha beta agaciro kegereye ubushyuhe bwakoreshejwe mumushinga. Datasheets nyinshi za thermistor zerekana agaciro ka beta hamwe no kwihanganira kwihanganira kuri 25 ° C no kwihanganira agaciro ka beta.
Ubushyuhe bwo hejuru cyane hamwe nibisubizo bihanitse nkibisubizo bya Omega 44xxx ikoresha ikigereranyo cya Steinhart-Hart kugirango uhindure guhangana na dogere selisiyusi. Ikigereranyo cya 2 gisaba ibintu bitatu A, B, na C, byongeye gutangwa nuwakoze sensor. Kuberako coefficient zingana zingana hakoreshejwe ingingo eshatu zubushyuhe, ikigereranyo cyavuyemo kigabanya ikosa ryatangijwe numurongo (mubisanzwe 0.02 ° C).
A, B na C nibisanzwe biva mubice bitatu byubushyuhe. R = kurwanya thermistor muri ohms T = ubushyuhe muri dogere K.
Ku mutini. 3 yerekana ibyishimo byubu bya sensor. Imiyoboro ya Drive ikoreshwa kuri thermistor kandi icyerekezo kimwe gikoreshwa kuri résistoriste neza; résistoriste idasobanutse ikoreshwa nkibisobanuro byo gupima. Agaciro kerekana rezistoriste igomba kuba irenze cyangwa ingana nagaciro gakomeye ko kurwanya thermistor (bitewe nubushyuhe buke bwapimwe muri sisitemu).
Mugihe uhitamo ibyishimo, imbaraga ntarengwa za thermistor zigomba kongera kwitabwaho. Ibi byemeza ko voltage hejuru ya sensor hamwe na rezo irwanya buri gihe kurwego rwemewe na electronics. Umwanya uriho isoko isaba icyumba kimwe cyangwa ibisohoka bihuye. Niba thermistor ifite imbaraga nyinshi kurwego rwo hasi rushobora gupimwa, ibi bizavamo umuvuduko muke cyane. Kubwibyo, voltage ikomoka kuri thermistor ku bushyuhe bwo hejuru ni nto. Gahunda yo kunguka ibyiciro irashobora gukoreshwa mugutezimbere ibipimo byibi bimenyetso byo hasi. Nyamara, inyungu igomba gutegurwa muburyo bukomeye kuko urwego rwibimenyetso ruva muri thermistor rutandukana cyane nubushyuhe.
Ubundi buryo ni ugushiraho inyungu ariko ukoreshe dinamike igezweho. Kubwibyo, nkuko urwego rwikimenyetso ruva muri thermistor ruhinduka, agaciro ka drayike igenda ihinduka kuburyo bugaragara kuburyo voltage yateye imbere muri thermistor iri murwego rwinjiza rwibikoresho bya elegitoroniki. Umukoresha agomba kwemeza ko voltage yateye imbere murwego rwo kurwanya nayo iri kurwego rwemewe na electronics. Amahitamo yombi arasaba urwego rwo hejuru rwo kugenzura, guhora ukurikirana voltage hejuru ya thermistor kugirango electronics ibashe gupima ibimenyetso. Hariho inzira yoroshye? Tekereza kubyishimo bya voltage.
Iyo imbaraga za DC zashyizwe kuri thermistor, umuyoboro unyuze muri thermistor uhita upima uko kurwanya thermistor bihinduka. Noneho, ukoresheje ibipimo bipima neza birwanya aho kwifashisha, intego yabyo ni ukubara umuyaga unyura muri thermistor, bityo ukemerera kurwanya thermistor kubara. Kubera ko moteri ya voltage nayo ikoreshwa nkikimenyetso cya ADC, nta nyungu isabwa. Utunganya ntabwo afite akazi ko kugenzura voltage ya thermistor, kumenya niba urwego rwibimenyetso rushobora gupimwa na electronics, no kubara icyo inyungu yunguka / agaciro kigezweho igomba guhinduka. Ubu ni bwo buryo bukoreshwa muri iyi ngingo.
Niba thermistor ifite igipimo gito cyo kurwanya no guhangana, voltage cyangwa ibyishimo byubu birashobora gukoreshwa. Muri iki kibazo, ibiyobora bigezweho ninyungu birashobora gukosorwa. Rero, umuzenguruko uzaba nkuko bigaragara ku gishushanyo cya 3. Ubu buryo buroroshye kuko birashoboka kugenzura imiyoboro ikoresheje sensor hamwe na rezistoriste, ifite agaciro mumashanyarazi make. Mubyongeyeho, kwishyushya kwa thermistor biragabanuka.
Umuvuduko wa voltage urashobora kandi gukoreshwa kuri thermistors hamwe nu rutonde rwo guhangana. Nyamara, uyikoresha agomba guhora yemeza ko ikigezweho binyuze muri sensor itari hejuru cyane kuri sensor cyangwa progaramu.
Umuvuduko wa voltage worohereza ishyirwa mubikorwa mugihe ukoresheje thermistor ifite igipimo kinini cyo guhangana nubushyuhe bugari. Kurwanya izina rinini bitanga urwego rwemewe rwibipimo bigezweho. Ariko, abashushanya bakeneye kwemeza ko ikigezweho kiri kurwego rwemewe kurwego rwubushyuhe bwose rushyigikiwe na porogaramu.
Sigma-Delta ADCs itanga ibyiza byinshi mugushushanya sisitemu yo gupima thermistor. Ubwa mbere, kubera ko sigma-delta ADC isubiramo ibyinjira byinjira, kuyungurura hanze bigumishwa byibuze kandi igisabwa gusa ni akayunguruzo ka RC. Zitanga guhinduka muburyo bwa filteri nibisohoka baud igipimo. Byubatswe mububiko bwa digitale birashobora gukoreshwa muguhagarika intambamyi zose zikoreshwa mumashanyarazi. Ibikoresho 24-bit nka AD7124-4 / AD7124-8 bifite ibyemezo byuzuye bigera kuri 21.7 bits, bityo bitanga ibyemezo bihanitse.
Gukoresha sigma-delta ADC yoroshya cyane igishushanyo mbonera cya thermistor mugihe ugabanya ibisobanuro, igiciro cya sisitemu, umwanya wibibaho, nigihe cyo kwisoko.
Iyi ngingo ikoresha AD7124-4 / AD7124-8 nka ADC kubera ko ari urusaku ruke, umuyaga muke, ADC itomoye neza yubatswe muri PGA, yubatswe, yerekanwe, iyinjiza, hamwe na buffer yerekana.
Utitaye ku kuba ukoresha amashanyarazi ya moteri cyangwa moteri ya voltage, iboneza rya ratiometric birasabwa aho voltage voltage na sensor voltage biva mubisoko bimwe. Ibi bivuze ko impinduka iyo ari yo yose ituruka ku byishimo bitazagira ingaruka ku bipimo bifatika.
Ku mutini. 5 yerekana imiyoboro ihoraho ya thermistor hamwe na résistoriste ya RREF, voltage yakozwe muri RREF ni voltage yerekana gupima thermistor.
Umwanya uriho ntukeneye kuba nyayo kandi urashobora kuba udahagaze neza kuko amakosa yose mumurima agezweho azakurwaho muriyi miterere. Mubisanzwe, ibyishimo byubu bikundwa kuruta gushimishwa na voltage kubera kugenzura ibyiyumvo birenze urugero hamwe nubudahangarwa bw urusaku mugihe sensor iba iri ahantu kure. Ubu bwoko bwo kubogama bukoreshwa mubisanzwe kuri RTDs cyangwa thermistors ifite agaciro gake. Nyamara, kuri thermistor ifite agaciro gakomeye ko kurwanya no kwiyumvamo ibintu byinshi, urwego rwibimenyetso rwatewe na buri mpinduka yubushyuhe ruzaba runini, bityo imbaraga za voltage zikoreshwa. Kurugero, 10 kΩ thermistor ifite ubukana bwa 10 kΩ kuri 25 ° C. Kuri -50 ° C, kurwanya ubushyuhe bwa NTC ni 441.117 kΩ. Imiyoboro ntoya ya 50 µA yatanzwe na AD7124-4 / AD7124-8 itanga 441.117 kΩ × 50 µA = 22 V, ikaba ari ndende cyane kandi hanze yimikorere ya ADC iboneka cyane ikoreshwa muriki gice gisaba. Thermistors nayo isanzwe ihujwe cyangwa iherereye hafi ya elegitoroniki, bityo ubudahangarwa bwo gutwara amashanyarazi ntibusabwa.
Ongeraho imyumvire irwanya urukurikirane nka voltage igabanya umuzenguruko bizagabanya imiyoboro ikoresheje thermistor kugeza ku giciro cyayo cyo kurwanya. Muri iyi miterere, agaciro k'imyumvire irwanya RSENSE igomba kuba ingana nagaciro k’ubushyuhe bwa thermistor ku bushyuhe bwa dogere 25 ° C, kugirango ingufu zisohoka zizaba zingana na hagati ya voltage yerekanwe ku bushyuhe bwayo bwa nomero ya 25 ° CC Muri ubwo buryo, niba hakoreshejwe 10 kΩ ya termistor hamwe na 10 kΩ kuri 25 ° C, RSENSE igomba kuba 10 kΩ. Mugihe ubushyuhe bugenda buhinduka, ubukana bwa thermistor ya NTC nabwo burahinduka, kandi ikigereranyo cyumubyigano wa moteri hejuru ya thermistor nacyo kirahinduka, bikavamo voltage isohoka ihwanye nuburwanya bwa thermistor ya NTC.
Niba ibyatoranijwe byatoranijwe bikoreshwa mugukoresha ingufu za thermistor na / cyangwa RSENSE bihuye na ADC yerekana imbaraga zikoreshwa mugupima, sisitemu yashizwe kubipimo bya ratiometric (Igicapo 7) kugirango inkomoko iyo ari yo yose iterwa no gushimisha inkomoko ya voltage izabogama kugirango ikureho.
Menya ko haba imyumvire irwanya (voltage itwarwa) cyangwa irwanya résistance (ikoreshwa nubu) igomba kugira kwihanganira bike kwambere hamwe na drift nkeya, kuko impinduka zombi zishobora kugira ingaruka kuri sisitemu yose.
Iyo ukoresheje thermistors nyinshi, voltage imwe yo kwishima irashobora gukoreshwa. Nyamara, buri thermistor igomba kugira ibyiyumvo byayo bidasobanutse, nkuko bigaragara mumitini. 8. Ubundi buryo ni ugukoresha Multiplexer yo hanze cyangwa irwanya imbaraga nke muri leta, itanga gusangira imyumvire imwe idasobanutse. Hamwe nibi bikoresho, buri thermistor ikenera igihe cyo gutuza iyo ipimwe.
Muncamake, mugihe utegura sisitemu yo gupima ubushyuhe bwa thermistor, haribibazo byinshi ugomba gusuzuma: guhitamo sensor, insinga za sensor, guhitamo ibicuruzwa, ibicuruzwa bya ADC, nuburyo izo mpinduka zitandukanye zigira ingaruka muburyo rusange bwa sisitemu. Ingingo ikurikira muri uru ruhererekane isobanura uburyo bwo kunoza igishushanyo cya sisitemu hamwe ningengo yimikorere ya sisitemu kugirango ugere kubikorwa byawe.
Igihe cyo kohereza: Nzeri-30-2022