đề cương đo lường

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    1. Khi nim v cm bin? Phn loi cm bin? cc vn khi thit k v sdng cm bin

    Tr li:Cm bin l mt thit b chu tc ng ca cc i lng vt l cn o m khng c tnh

    cht in v cho ta u ra mt i lng mang bn cht in ( nh in tch, in p,

    dng in , tr khng ) k hiu l s

    c trng in s l hm ca i lng cn o m :S=f(m)

    Quan h gia s v m c th l tuyn tnh hay phi tuyn . Song trong thc t d sdng thng thng ngi ta ch to cm bin sao cho c s lin h tuyn tnh gia binthin u ra v bin thin u vo . s=s *m

    Trong S gi l nhy ca cm bin Phn bit cm bin :

    - phn loi: cm bin tch cc v cm bin th ng.+cm bin tch cc l cc loi cm bin hot ng nh mt my pht in, v mt nguynl n thng da trn cc hiu ng vt l bin i mt dang nng lng no (nhnhit,c,quang) thnh nng lng in.+cm bin th ng l loi cm bin c ch to t cc vt liu c nhng thng s trkhng nhy vi cc i lng o. Gi tr ca tr khng ca cm bin khng nhng phthuc vo hnh dng, kch thc m cn ph thuc vo tnh cht in ca vt liu nh:in tr sut, t thm, hng s in mi-cc vn khi thit k v s dng cm bin:+cc i lng nh hng ti cm binNhit lm thay i cc c trng in, c v kch thc ca cm bin.

    m c th lm thay i tnh cht in ca vt liu :p sut, gia tc, dung gy nn bin dng hoc ng sut trongT trng c th gy nn sc in ng cm ng chng chnh ln tn hiu c ch+sai s ca php o: sai s ca h thng v sai s ngu nhin+ nhy ca cm bin+ nhanh-thi gian hi p.

    2.Cm bin quang hot ng da trn nguyn l g? Ngun sng ca cm binquang trong thc t l loi g?Tr li:

    Cm bin quang hot ng da trn nguyn l:- Trong vt cht cc in t bao quanh ht nhn nh mt lc lin kt vi ht nhn

    We , lc ny mnh vi cc in t trong lp trong v yu vi in t lp ngoi ,do cc in t lp ngoi tch khi nguyn t . Khi nh sng chiu ln vtcht nu nng lng ca cc photo ln cp cho in t thng lc lin kt thcc in t trong vt cht s c gii phng tr thnh in t t do.

    - in tch c gii phng do chiu sng ph thuc vo bn cht ca vt b chiusng.

    Cm bin quang hot ng da trn nguyn l ny.

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    Ngun sng ca cm bin quang trong thc t hu ht dng nh sng hng ngoi

    3 Ngi ta phn loi cm bin quang da trn nguyn tc no? c im cami loi? Loi no c khong cch pht hin xa nht?

    Tr li:

    Ngi ta phn loi cm bin quang da trn nguyn tc :Phn loi theo ngun sng gia phn pht v phn thu:- Thu tch bit- Thu pht mt pha s dng gng phn x- Thu pht mt pha s dng phn x khuch tn.

    c im ca mi loi:-Thu pht c lp : B pht v thu nm cc thit b c lp nhau to ra nh sng

    b thu c cng ln nht , phn bit sng ti cao, pht hin c vt th khngph thuc vo mu sc v b mt vt th, gi thnh cao.- Cm bin phn x gng: khong cch pht hin ln , kh nng phn bit cao , cth phn bit c vt th trong sut , m, bng gi thnh r hn cm bin thu pht

    c lp , tin cy cao-Cm bin loi pht x khuch tn : Ch pht hin vt th trong vng gii hn , b nhhng ca mu nn sau vng cm bin , l tng cho nhiu ng dng cn trit tiunn- Loi c khong cch pht hin xa nht l cm bin thu pht c lp

    Cu 4:K hiu ca cm bin quang:-Nng lng bc x: Q l nng lng phn x lan truyn hoc bc x di dng

    bc x n v l J hoc lm.s- Thng lng nh sng : l cng sut pht x , lan truyn hoc hp th , n v

    l W hay lm

    - Cng nh sng : I l lung nng lng pht theo 1 hng di mt n vgc khi , n v W/sv hoc Cd.- chi L l t s gia cng nh sng phn x bi mt b mt theo 1 hng

    xc nh v din tch h/c ca pt ny trn mp vung gc vi hng , n vW/m2 hoc lm/m2

    Cu 5: Trn thn cm bin c ghi :Dark on : khi pht hin vt s cho tn hiu off, khng c vt cho tn hiu onLight on: Khi pht hin vt s cho tn hiu On , khng c vt cho tn hiu Off.Cu 6: Khi mc song song nhiu cm bin quang thu pht tch bit , chng nhiu taphi o v tr phn thu v phn pht .Cu 7: Nguyn l hot ng ca cm bin si quang:

    CB si quang l 1 dng ca cm bin quang , nh sng s dng trong cm bin quang lnh sng hng ngoi hoc lazer. nh sng pht ra thit b pht c dn truyn qua 1si quang a n u pht , nh sng p vo vt th phn x li u thu , qua si quangv mch x l .*c im ca cm bin si quang:- Pht hin vt c kch thc nh , thi gian p ng nhanh , pht hin chnh xc ngay ctrong khi iu kin khng CB. Thu pht ln ti 1100mm, phn x khuch i ln ti130mm, phn x xc nh pht hin 6mm.

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    Cu 8 : Nguyn l hot ng ca cm bin lazer:Cm bin gm phn t pht lazer , phn t cm nhn v gng. Ngun sng pht ragng 1 phn v chiu vo i tng .Sng phn hi t i tng s giao thoa vi sngpht ra. Nu cc nh sng cng nhau th sng giao thoa c bin gp i bin banu . nu sng phn hi lch pha 1800 th bin sng giao thoa bng 0.

    c im:Ngun sng lazer rt n sc , nh hng cao, c kh nng truyn rt xa do thng s dng lm CB phn bit mu , nhn bit hnh dng sn phm.

    Cu 9:Cm bin quang c kh nng pht hin kch thc vt th l cm bin lazer.Cm bin c kh nng pht hin vt th gc khut l cm bin thu pht tch bit v cmbin phn x gng .Cm bin c kh nng pht hin vt th c h s hp th nh sng lnCu 10:Trong cc thit b iu khin t xa , phn t nhy sng l : phototranzitorCu 11:

    Nu c im ca cng tc hnh trnh? Nu ti l rle xoay chiu th c th s dngcng tc hnh trnh ng/ ngt c khng? Nu cch u ni ti vi tip imthng m?c im ca cng tc hnh trnh :Cng tc hnh trnh dng nhn bit v tr chuyn ng ca c cu my . Cng tc hnhtrnh l mt tip im c kh do tui th khng cao , khng dng c trong mitrng du, m, ha cht .

    Cu 12:Nu cu to ca cng tc t? V k hiu ca cng tc t? Trong thc t c cng tct dng tip im thng ng khng? Nu c th cu to ca n nh th no? Cu to ca cng tc t :Cu to ca cng tc t gm c mt tip im li g c dt trong mt bng thytinh rt chn khng v mt nam chm vnh cu > khi tip im li g gn nam chmvnh cu th lc t trng do nam chm sinh ra s ht tip im ng li .K hiu:

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    Cu 13:Nu c im ng dng ca cng tc t?

    - Cng tc t c tip im t trong bng thy tinh kn nn c th chu c trongmi trng du , m , ha cht . Trong thc t , cng tc t c ng dng nhiu

    trong cng nghip nh ch to cm bin mc , nhn bit v tr ca cc chi tit my. c bit trong h thng iu khin kh nn cng tc t c s dng rt phbin nhn bit v tr ca piton chuyn ng trong xilanh.

    Cu 14:cm bin tim cn in cm c c im g? Khong cch pht hin cacm bin tim cn in cm ph thuc vo yu t no? Cm bin chu nh

    hng ca nhiu no nht? cch khc phc?Tr li:Cm bin tim cn, in cm c c im:u d ca cm bin thng c s dng l mch t h lm bng li st hoc Perit.Trn mch t c cun dy in t . Nu 1 vt kim loi dn in ni kn mch khet h th gi tr in cm ca u d in cm s gim , dng in tiu th tng nucp u d in p xoay chiu.

    Khong cch pht hin ca cm bin tim cn in cm ph thuc vo kch thc ,hnh dng vt v dn t ca cv vt th , nhit mi trng

    Cm bin tim cn in cm nh hng bi nhiu, khc phc bng cch bc v kimloi cho cm bin v ni t

    Cu 15:cm bin tim cn in dung c c im g? Khong cch pht hin ca cmbin tim cn in dung ph thuc vo yu t no? Cm bin chu nh hng canhiu no nht? cch khc phc?

    Tr li:Cm bin in cm in dung c c im:Thng l 2 l ng c in tch b mt l 10cm2 dn trn lp Perit cch in hocnha cch in , cm bin tim cn in dung c th xc nh c tt c cc vt c hs in mi khc vi mi trng in mi ngoi khng kh , xc nh c mc tn sthay i Khong cch pht hin hiu qu ca cm bin in dung ph thuc vo m v

    sng Cm bin chu nh hng ca nhiu. Cch khc phc :

    Cu 16:Mun pht hin vt th hoc cht liu ng trong hp kn th s dng cmbin no? C yu cu g khng?

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    Mun pht hin vt th hoc cht liu ng trong hp kn th s dng cm bin tim cnin dung.Yu cu vt th hoc cht liu cha trong thng l cc phi kim loi .Cu 17: Mun nhn bit vt th kim loi n gn c th s dng loi cm bin no?Khong cch ti a t cm bin n vt th l bao nhiu?

    Tr li :Mun nhn bit kim loi n gn c th s dng loi cm bin tim cn in cm .Khong cch ti a c th ln n 1m.Cu 18: C th s dng cm bin tim cn in dung lm cm bin o mc c khng?Yu cu c th o c nh th no?Tr li:C th s dng cm bin tim cn in dung lm cm bin o mcYu cu o c:i vi cht lng cch in : t 2 in cc kim loi thng ng trong bnh cha dungdch trong bnh chnh l in mi.

    i vi cht lng dn in : s dng cm bin in dung gn ln thnh bnh.o lin tc : Dng 2 que o,1 que o c bc cch in bng lp in mi , mt que okhng bc cch in.Cu 19: c th o c lu lng cht lng bng lu lng k in t, yu cu v chtlng y nh th no?Tr li: o c lu lng cht lng bng lu lng k in t , yu cu v cht lng c dn in khng nh hn 10-5 10-6 siemen/m.Cu 20:Cch u ni ti ca cm bin tim cn in cm c u ra kiu PNP.

    Cu 21:Cch u ni vi ti ca cm bin tim cn in cm c u ra kiu PNP?

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    Cu 22: Cm bin tim cn in dung l loi cm bin tch cc v n c s bin i nnglng . Khi c 1 vt kim loi n gn nng lng ca b dao ng b tiu hao to nncc dng xoay c cm ng bn trong vt th .

    Cu 23: Cm bin tim cn in cm l cm bin tch cc hay th ng? ti sao?

    Cu 24:

    Cu 25: Cm bin siu m hot ng da trn nguyn tc no? Nu c im cacm bin siu m?Tr li:Nguyn tc hot ng:Khi c lnh yu cu o b iu khin s pht lnh pht ra chu k sng m bc x ra bnngoi khi gp vt chn s phn x tr li b thu. Da vo vn tc t sng v qung thigian t khi pht sng siu m ti khi nhn li suy ra khong cch t vt ti v tr tcm bin c im ca cm bin siu m.

    - Khong cch bt vt ln t 2mm-10m thm ch 100m- Dng sng siu m vi tn s ngoi ngng nghe ca tai ngi bt vt- L cm bin thng minh.

    Cu 26:Cm bin mc kiu phao c kh thng c ng dng u? N dng ongng hay o lin tc?Tr li:Cm bin phao c kh thng c ng dng trong h thng bm nc tng ca nh cao tng.

    - N c s dng o

    Cu 27:Yu cu cht lng ca cm bin mc kiu in dn l g?

    - Ch ng dng o cc cht lng dn in khng c tnh n mn v khng lncc vt th cch in nh du nhn .

    Cu 28 :

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    o 3 ngng trong bnh v bng nha dng cm bin in dn cn 4 in cc v cncc gc t y bnh , 3 cc cn li P1, P2, P3 c gn cc v tr m ta cn xc nhmcCu 29 : TNG T 28Cu 30:

    Ngun nui cho cc in cc ca cm bin mc kiu in dn c c im g? Tisao?- ngun xoay chiu 10v v: chng hin tng phn ly

    Cu 31:Khi o mc cht lng cch in 1 cch lin tc bng phng php thay i indung, ngi ta xc nh mc thng qua hnh thc no?Tr li:

    - Khi o mc cht lng cch in 1 cch lin tc bng phng php thay i indung , ngi ta xc nh mc bng cch t 2 in cc ca kim loi ca cm binthng ng trong bnh cha dung dch , nh vy khi dung dch trong bnh bay hihay kt ta s l cho in tch bn cc thay i theo. Sau dng 1 mch in t

    xc nh s thay i ca in dung suy ra mc cht lng trung bnh .Cu 32: Khi o mc cht lng dn in 1 cch lin tc bng phn