Ichi ndicho chinyorwa chekutanga muzvikamu zviviri zvakatevedzana.Ichi chinyorwa chichatanga kukurukura nhoroondo uye kugadzirisa matambudziko ethermistor-based tembirichakuyerwa masisitimu, pamwe nekuenzanisa kwavo neresistance thermometer (RTD) tembiricha yekuyera masisitimu.Ichatsanangurawo sarudzo ye thermistor, kumisikidza kutengeserana-offs, uye kukosha kwe sigma-delta analog-to-digital converters (ADCs) munzvimbo ino yekushandisa.Chinyorwa chechipiri chinotsanangura maitiro ekugadzirisa uye kuongorora iyo yekupedzisira-yakavakirwa thermistor-yakavakirwa kuyerwa system.
Sezvakatsanangurwa mune yakapfuura chinyorwa nhevedzano, Optimizing RTD Temperature Sensor Systems, iyo RTD inopikisa iyo inopikisa inosiyana nekupisa.Thermistors inoshanda zvakafanana neRTDs.Kusiyana neRTDs, iyo ine chete yakanaka tembiricha coefficient, thermistor inogona kuva yakanaka kana yakaipa tembiricha coefficient.Negative tembiricha coefficient (NTC) thermistors inodzikisira kuramba kwayo sezvo tembiricha inokwira, nepo positive tembiricha coefficient (PTC) thermistors inowedzera kusada kwadzo sezvo tembiricha inokwira.Pamusoro pemuonde.1 inoratidza maitiro ekupindura eyakajairwa NTC uye PTC thermistors uye inoaenzanisa neRTD curves.
Panyaya yetembiricha renji, iyo RTD curve inosvika mutsara, uye sensor inovhara yakafararira tembiricha renji pane thermistors (kazhinji -200 ° C kusvika + 850 ° C) nekuda kweiyo isiri-mutsara (exponential) hunhu hwe thermistor.MaRTD anowanzo kupihwa mune anozivikanwa akajairika macurves, nepo thermistor curves inosiyana nemugadziri.Isu tichakurukura izvi zvakadzama mune thermistor sarudzo yekutungamira chikamu chechinyorwa ichi.
Thermistors anogadzirwa kubva mumubatanidzwa zvinhu, kazhinji ceramics, polymers, kana semiconductors (kazhinji metal oxides) uye simbi dzakachena (platinum, nickel, kana mhangura).Thermistors inogona kuona shanduko yekushisa nekukurumidza kupfuura RTDs, ichipa nekukurumidza mhinduro.Naizvozvo, thermistors anowanzo shandiswa nemasensor mumashandisirwo anoda mutengo wakaderera, saizi diki, kukurumidza kupindura, kunzwisiswa kwepamusoro, uye tembiricha shoma, senge magetsi ekudzora, imba uye kutonga kwekuvaka, sainzi marabhoritari, kana kutonhora junction muripo kune thermocouples mune zvekutengesa. kana kushandiswa kwemaindasitiri.zvinangwa.Applications.
Kazhinji, NTC thermistors inoshandiswa kuyera tembiricha chaiyo, kwete PTC thermistors.Mamwe maPTC thermistors aripo anogona kushandiswa mumaseketi ekudzivirira anodarika kana semafusi anogadzika patsva ekuchengetedza maapplication.The resistance-temperature curve yePTC thermistor inoratidza dunhu diki diki reNTC risati rasvika painochinja (kana kuti Curie point), pamusoro payo kupokana kunokwira zvakanyanya nemirairo yakawanda yehukuru muhuwandu hwemadhigirii akati wandei.Pasi pemamiriro ekunze, iyo PTC thermistor ichagadzira yakasimba yekuzvipisa kana tembiricha yekuchinja yakapfuura, uye kushorwa kwayo kuchakwira zvakanyanya, izvo zvinoderedza kupinza ikozvino kune system, nekudaro kudzivirira kukanganisa.Iko kuchinjika kwePTC thermistors kunowanzo pakati pe60 ° C uye 120 ° C uye haina kukodzera kudzora kuyerwa kwetembiricha mune dzakasiyana siyana dzekushandisa.Chinyorwa ichi chakanangana neNTC thermistors, iyo inogona kuyera kana kutarisa tembiricha kubva -80°C kusvika +150°C.NTC thermistors ine zviyero zvekupikisa kubva pashoma ohms kusvika 10 MΩ pa25°C.Sezvinoratidzwa mufig.1, shanduko yekupokana padhigirii Celsius yemathermistors inonyanya kutaurwa pane yekupikisa mathermometers.Kuenzaniswa ne thermistors, iyo thermistor yakakwira senitivity uye yakakwirira kuramba kukosha inorerutsa yayo yekuisa dunhu, sezvo thermistors haidi chero yakakosha wiring kumisikidzwa, senge 3-waya kana 4-waya, kubhadhara kutungamira kuramba.Iyo thermistor dhizaini inoshandisa chete yakapusa 2-waya kumisikidzwa.
Yakakwira-chaiyo thermistor-yakavakirwa tembiricha kuyerwa kunoda chaiyo chiratidzo chekugadzirisa, analog-to-digital shanduko, mutsara, uye muripo, sezvakaratidzwa mufig.2.
Kunyangwe iyo cheni yechiratidzo ingaite seyakapusa, kune akati wandei akaomarara anokanganisa saizi, mutengo, uye kuita kweiyo mamaboard yese.ADI's precision ADC portfolio inosanganisira akati wandei akabatanidzwa mhinduro, senge AD7124-4/AD7124-8, iyo inopa akati wandei mabhenefiti eiyo thermal system dhizaini sezvo mazhinji ezvivharo zvekuvaka anodiwa pakunyorera akavakirwa-mukati.Nekudaro, kune akasiyana matambudziko mukugadzira uye optimize thermistor-yakavakirwa tembiricha kuyerwa mhinduro.
Chinyorwa ichi chinokurukura imwe neimwe yenyaya idzi uye chinopa kurudziro yekuzvigadzirisa uye zvakare kurerutsa magadzirirwo emasisitimu akadaro.
Kune zvakawanda zvakasiyana-siyana zveNTC thermistorspamusika nhasi, saka kusarudza iyo thermistor chaiyo yekushandisa kwako kunogona kuve basa rinotyisa.Ziva kuti ma thermistors akanyorwa nehuwandu hwawo hwezita, kunova kushora kwavo kwezita pa25 ° C.Naizvozvo, 10 kΩ thermistor ine zita rekudzivirira kwe10 kΩ pa25°C.Thermistors ine mazita kana ekutanga kuramba kukosha kubva kune mashoma ohms kusvika 10 MΩ.Mathermistors ane low resistance ratings (nominal resistance ye10 kΩ kana pasi) anowanzo tsigira tembiricha yakaderera, senge -50°C kusvika +70°C.Mathermistor ane mwero wepamusoro wekupokana anogona kushingirira tembiricha inosvika 300°C.
Iyo thermistor element inogadzirwa nesimbi oxide.Thermistors inowanikwa mubhora, radial uye SMD maumbirwo.Thermistor beads ari epoxy coated kana girazi akavharidzirwa kuti awedzere dziviriro.Epoxy coated ball thermistors, radial uye surface thermistors inokodzera tembiricha inosvika 150°C.Glass bead thermistors akakodzera kuyera tembiricha yepamusoro.Mhando dzese dzekupfeka / kurongedza dzinodzivirirawo kubva mukuora.Mamwe ma thermistors anozoitawo mamwe dzimba dzekuwedzera dziviriro munzvimbo dzakaoma.Bead thermistors vane kukurumidza kupindura nguva kupfuura radial/SMD thermistors.Zvisinei, hadzina kusimba.Nokudaro, rudzi rwe thermistor rinoshandiswa rinoenderana nekuguma kwekushanda uye nzvimbo iyo thermistor iripo.Kugadzikana kwenguva refu kweiyo thermistor kunoenderana nezvinhu zvayo, kurongedza, uye dhizaini.Semuenzaniso, epoxy-coated NTC thermistor inogona kuchinja 0.2 ° C pagore, nepo thermistor yakavharwa inongochinja 0.02 ° C pagore.
Thermitors inouya nenzira dzakasiyana.Standard thermistor inowanzova nekururama kwe 0.5°C kusvika 1.5°C.Thermistor resistance rating uye beta value (reshiyo ye25°C kusvika 50°C/85°C) ine kushivirira.Ziva kuti kukosha kwebeta kweiyo thermistor kunosiyana nemugadziri.Semuyenzaniso, gumi kΩ NTC mathermistors kubva kune vakasiyana vagadziri achave akasiyana beta kukosha.Kuti uwane mamwe masystem, ma thermistors akadai seOmega ™ 44xxx akatevedzana anogona kushandiswa.Vane huchokwadi hwe0.1°C kana 0.2°C pamusoro petembiricha ye0°C kusvika 70°C.Naizvozvo, huwandu hwetembiricha hunogona kuyerwa uye iko kurongeka kunodiwa pamusoro peiyo tembiricha renji inotarisisa kana ma thermistor akakodzera pakushandisa uku.Ndokumbira utarise kuti kukwirisa kweiyo Omega 44xxx nhevedzano, kunowedzera mutengo.
Kushandura kuramba kune madhigirii Celsius, kukosha kwebeta kunowanzoshandiswa.Kukosha kwebeta kunotarwa nekuziva iwo maviri tembiricha mapoinzi uye anowirirana kuramba pane imwe neimwe tembiricha.
RT1 = Kudzivirirwa kwekushisa 1 RT2 = Kuramba kwekushisa 2 T1 = Kupisa 1 (K) T2 = Kupisa 2 (K)
Mushandisi anoshandisa kukosha kwebeta iri padyo netembiricha yakashandiswa mupurojekiti.Mazhinji thermistor datasheet anonyora kukosha kwebeta pamwe nekuramba kushivirira pa25°C uye kushivirira kukosha kwebeta.
Mabatirwo emhando yepamusoro-soro uye magadzirirwo ekugadzirisa akakwenenzverwa akadai seOmega 44xxx akatevedzana anoshandisa Steinhart-Hart equation kushandura kuramba kuita madhigirii Celsius.Equation 2 inoda matatu anogara A, B, uye C, zvakare akapihwa nemugadziri we sensor.Nekuti iyo equation coefficients inogadzirwa uchishandisa matatu tembiricha mapoinzi, mhedzisiro equation inoderedza kukanganisa kwakaunzwa nemutsara (kazhinji 0.02 °C).
A, B uye C ndiwo anogara akatorwa kubva kune matatu tembiricha setpoints.R = thermistor kuramba mu ohms T = tembiricha muK madhigirii
Pamusoro pemuonde.3 inoratidza kufara kwazvino kwe sensor.Dhiraivha ikozvino inoshandiswa kune thermistor uye yakafanana ikozvino inoshandiswa kune yakarurama resistor;chidziviso chechokwadi chinoshandiswa sechirevo chekuyera.Kukosha kwereferensi resistor kunofanirwa kuve kwakakura kudarika kana kuenzana nemutengo wepamusoro weiyo thermistor kuramba (zvinoenderana neyakadzikira tembiricha yakayerwa muhurongwa).
Paunosarudza ikozvino kunakidza, kupikisa kwakanyanya kwe thermistor kunofanira kutorwa zvakare.Izvi zvinogonesa kuti iyo voltage pa sensor uye referensi resistor inogara iri padanho rinogamuchirwa kune zvemagetsi.Iyo munda ikozvino sosi inoda imwe headroom kana inobuda inoenderana.Kana iyo thermistor ine yakanyanya kupikisa pane yakaderera kuyerwa tembiricha, izvi zvinokonzeresa yakaderera dhiraivha ikozvino.Naizvozvo, iyo voltage inogadzirwa mhiri kwe thermistor pakupisa kwakanyanya idiki.Programmable nhanho dzekuwana dzinogona kushandiswa kukwenenzvera kuyerwa kweaya masaini masaini.Nekudaro, iyo pfuma inofanirwa kurongwa zvine simba nekuti iyo chiratidzo chechiratidzo kubva kune thermistor inosiyana zvakanyanya nekushisa.
Imwe sarudzo ndeye kuseta kuwana asi shandisa dynamic drive ikozvino.Naizvozvo, sezvo chiyero chechiratidzo kubva kune thermistor chinoshanduka, dhiraivha yazvino kukosha inochinja zvine simba kuitira kuti voltage inogadzirwa pane iyo thermistor iri mukati meyakatsanangurwa yekuisa renji yemagetsi mudziyo.Mushandisi anofanirwa kuve nechokwadi chekuti voltage yakagadziridzwa pane referensi resistor iri zvakare pamwero unogamuchirwa kune zvemagetsi.Zvose zvingasarudzwa zvinoda kukwirira kwepamusoro, kutarisa nguva dzose yevoltage pamhiri pe thermistor kuitira kuti magetsi akwanise kuyera chiratidzo.Pane imwe sarudzo iri nyore here?Funga nezvekuwedzera kwevoltage.
Kana magetsi eDC akaiswa kune thermistor, yazvino kuburikidza neiyo thermistor inongozviyeresa sezvo kuramba kweiyo thermistor kuchichinja.Ikozvino, uchishandisa yakanyatso kuyera resistor pachinzvimbo chereferensi referensi, chinangwa chayo ndechekuverenga ikozvino inoyerera kuburikidza ne thermistor, zvichibvumira iyo thermistor kuramba kuverengerwa.Sezvo dhiraivha yedhiraivha ichishandiswa zvakare sechiratidzo cheADC, hapana nhanho yekuwana inodiwa.Iyo processor haina basa rekutarisa iyo thermistor voltage, kuona kana iyo chiratidzo nhanho inogona kuyerwa nemagetsi, uye kuverenga kuti ndeipi drive kuwana / kukosha kwazvino kunoda kugadziriswa.Iyi ndiyo nzira inoshandiswa muchinyorwa chino.
Kana iyo thermistor iine diki yekupikisa chiyero uye renji rekudzivirira, voltage kana ikozvino excitation inogona kushandiswa.Muchiitiko ichi, dhiraivha ikozvino uye kuwana inogona kugadziriswa.Nokudaro, dunhu richava sezvakaratidzwa muMufananidzo 3. Iyi nzira yakanakira pakuti zvinokwanisika kudzora ikozvino kuburikidza ne sensor uye referensi resistor, iyo inokosha mumagetsi mashoma ekushandisa.Mukuwedzera, kuzvipisa kwe thermistor kunoderedzwa.
Voltage excitation inogona zvakare kushandiswa kune thermistors ine yakaderera kuramba ratings.Nekudaro, mushandisi anofanirwa kugara achiona kuti yazvino kuburikidza ne sensor haina kunyanya kukwira kune sensor kana application.
Voltage excitation inorerutsa kuita kana uchishandisa thermistor ine hombe yekupikisa chiyero uye tembiricha yakakura.Huru nominal resistance inopa chiyero chinogamuchirika cheyero yakayerwa ikozvino.Nekudaro, vagadziri vanofanirwa kuve nechokwadi chekuti ikozvino iri pamwero unogamuchirwa pamusoro pese tembiricha renji inotsigirwa nekushandisa.
Sigma-Delta ADCs inopa akati wandei mabhenefiti pakugadzira iyo thermistor kuyerwa system.Chekutanga, nekuti iyo sigma-delta ADC inodzokorora kupinza kweanalogi, kusefa kwekunze kunochengetwa kuri kushoma uye chinodiwa chete iri nyore RC sefa.Ivo vanopa kuchinjika mune sefa mhando uye inobuda baud mwero.Yakavakirwa-mukati kusefa kwedhijitari inogona kushandiswa kudzvanyirira chero kupindira mune mains powered zvishandiso.24-bit zvishandiso zvakaita seAD7124-4/AD7124-8 zvine chigadziriso chakazara chekusvika pa21.7 bits, saka zvinopa resolution yepamusoro.
Kushandiswa kwe sigma-delta ADC kunorerutsa zvakanyanya dhizaini ye thermistor uku ichidzikisa kutaurwa, mutengo wesystem, nzvimbo yebhodhi, uye nguva yekutengesa.
Ichi chinyorwa chinoshandisa iyo AD7124-4/AD7124-8 seADC nekuti iwo ruzha rwakadzika, yakaderera ikozvino, chaiyo ADCs ine yakavakirwa-mukati PGA, yakavakirwa-mukati referensi, analogi yekupinda, uye referensi buffer.
Kunyangwe iwe uri kushandisa dhiraivha yazvino kana dhiraivha voltage, ratiometric kumisikidza inokurudzirwa umo iyo referensi voltage uye sensor voltage inobva kune imwechete drive sosi.Izvi zvinoreva kuti chero shanduko mune yekukurudzira sosi haizokanganisa kurongeka kwechiyero.
Pamusoro pemuonde.5 inoratidza inogara ichidhiraivha ikozvino kune thermistor uye chaiyo resistor RREF, iyo voltage inogadzirwa mhiri kweRREF ndiyo inorevera voltage yekuyera thermistor.
Munda wazvino haudi kuve wakarurama uye unogona kunge usina kugadzikana sezvo chero zvikanganiso mumunda wezvino zvichabviswa mukugadziriswa uku.Kazhinji, kunakidzwa kwazvino kunosarudzwa pamusoro pekuwedzera kwevoltage nekuda kwehukuru hwekunzwa kutonga uye nani ruzha kusadzivirirwa kana sensor iri munzvimbo dziri kure.Iyi mhando yenzira yekurerekera inowanzo shandiswa kune RTDs kana thermistors ine yakaderera kushomeka kukosha.Nekudaro, kune iyo thermistor ine yakakwirira yekudzivirira kukosha uye yakakwirira senitivity, iyo nhanho yechiratidzo inogadzirwa nekushanduka kwetembiricha yega yega ichave yakakura, saka voltage excitation inoshandiswa.Semuenzaniso, 10 kΩ thermistor ine resistance ye10 kΩ pa25°C.Pa -50 ° C, kushorwa kweNTC thermistor ndeye 441.117 kΩ.Iyo idiki yekutyaira ikozvino ye50 µA yakapihwa neAD7124-4/AD7124-8 inogadzira 441.117 kΩ × 50 µA = 22 V, iyo yakanyanya kukwirisa uye kunze kwekushanda kweakawanda anowanikwa maADC anoshandiswa munzvimbo ino yekushandisa.Thermistors anowanzo akabatana kana kuwanikwa padyo nemagetsi, saka kusadzivirirwa kwekutyaira ikozvino hakudiwi.
Kuwedzera pfungwa resistor munhevedzano seyemagetsi divider redunhu inodzikamisa yazvino kuburikidza neiyo thermistor kune yayo kushoma kuramba kukosha.Muchigadziro ichi, kukosha kweiyo pfungwa resistor RSENSE kunofanirwa kuenzana nekukosha kwekupokana kwe thermistor pane tembiricha ye25 ° C, kuitira kuti magetsi ekubuda aenzane nepakati peiyo referensi voltage patembiricha yaro yezita. 25 ° CC Saizvozvowo, kana 10 kΩ thermistor ine kupesana kwe10 kΩ pa 25 ° C inoshandiswa, RSENSE inofanira kuva 10 kΩ.Sezvo tembiricha ichichinja, kuramba kweNTC thermistor zvakare kunoshanduka, uye chiyero cheiyo drive voltage pane thermistor inoshandukawo, zvichikonzera kuti magetsi ekubuda ave akaenzana nekupokana kweNTC thermistor.
Kana iyo yakasarudzwa voltage referensi inoshandiswa kusimbisa thermistor uye / kana RSENSE inoenderana neiyo ADC referensi voltage inoshandiswa kuyerwa, sisitimu inoiswa kune ratiometric kuyerwa (Figure 7) kuitira kuti chero excitation-inoenderana kukanganisa voltage sosi ichave yakarerekera kubvisa.
Ziva kuti ingave iyo pfungwa resistor (voltage driven) kana referensi resistor (ikozvino inotyairwa) inofanira kunge ine yakaderera yekutanga kushivirira uye yakaderera kukukurwa, sezvo zvese zviri zviviri zvinogona kukanganisa kurongeka kwehurongwa hwese.
Paunenge uchishandisa akawanda thermistors, imwe excitation voltage inogona kushandiswa.Nekudaro, yega yega thermistor inofanirwa kuve neyayo chaiyo yekunzwa inopikisa, sezvakaratidzwa muonde.8. Imwe sarudzo ndeye kushandisa yekunze multiplexer kana yakaderera-resistance switch in the on state, iyo inobvumira kugovera imwe yakarurama pfungwa resistor.Nekugadzirisa uku, imwe neimwe thermistor inoda imwe nguva yekugadzirisa kana kuyerwa.
Muchidimbu, paunenge uchigadzira iyo thermistor-based tembiricha yekuyera system, kune mibvunzo yakawanda yekufunga: sensor kusarudzwa, sensor wiring, chikamu chekusarudza kutengeserana-offs, ADC configuration, uye kuti izvi zvakasiyana-siyana zvinokanganisa sei kururamisa kwese kwehurongwa.Chinyorwa chinotevera mune ino nhevedzano chinotsanangura maitiro ekugadzirisa yako sisitimu dhizaini uye yakazara system yekukanganisa bhajeti kuti uwane yako chinangwa chekuita.
Nguva yekutumira: Sep-30-2022