CẢM BIẾN ÁP SUẤT

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  • L

    BI THO LUN MN:

    O LNG-CM BINDT2-K5

    CM BIN O P SUT

  • NHM VI1- L TH DUNG2- VNG S HI3- NGUYN TH HNG 4- NGUY N TH KIM HON5- MAI XUN MINH6- NGUYN TH M7- V VN TUYN8- NGUYN VN TUYN9- NGUYN VN TRNG10- V TH VNG

  • Ni dungI.Khi nim v o p sut 1.Khi nim v p sut2.n v o p sut3.Phn loi p sut,phng tin o p sut4.Cc cch o p sutII.Cng tc p sutCu to, c im,nguyn l hot ngIII.Mt s loi cm bin p sut1.Cm bin p sut mng sc co gin kim loiCu to, nguyn l, phn loi, c im ng dng2.Cm bin p in thch anhHiu ng p inNguyn l hot ng, c im, ng dngIV.ng dng thc t

  • 1.Khi nim v cm bin o p sut:Vic o c p sut ca cht kh, cht lng l cng vic bt buc trong thit k my mc c kh, cc dy chuyn sn xut s dng nng lng kh nn hay du thy lc.Trc y ngi ta s dng cc loi cm bin bng c hc, hin nay ngi ta s dng v pht trin cc loi cm bin o p sut c cht lng tt hn vi chnh xc cao hn v bn b hn cho cc cng vic kim sot v iu khin t xa cng vic t ng ha ton b h thng dy chuyn sn xut ca nh my.

  • Khc vi cc my o p xut c hc dng l xo v ch th trc tip qua mt h thng truyn ng c hc, cc loi cm bin o p sut bn dn u c mt phn t bn dn gn trn mng n hi bin i p sut thnh i lng in.Mt s loi cm bin p sut:

  • 2.p sut 1. nh ngha:p sut l lc tc dng trn mt n v din tch.P=F/A(P l p sut; F: lc; A: din tch tip xc)2. n v o: n v o p sut l Pascal (Pa)Pascal= Newton/m2Trong thc t ngi ta thng dng bi s ca n v Pascal l bar .1 bar = 105 N/m2 = 105 Pa. Ngoi ra 1atm 1 bar 1bar=14,504psi 1 atm = 14,696 psi

  • 3.Phn loi p sut

  • II.Phn loi phng tin o p sut:

    1.Da theo dng p sut :p k, p chn k: o p sut d.Kh p k (baromet): o p sut kh kh quyn.Chn khng k, p k ht: o p mp k hiu s: o p sut hiu o p sut tuyt i ta dng p k v kh p k khi p sut tuyt i ln hn p sut kh quyn. Hoc dng p k v chn khng k khi p sut tuyt i nh hn p sut kh quyn

  • 2.Theo nguyn l hot ng: C 5 nhm chnh:p k kiu l xop k pittongp k kiu cht lngp k theo nguyn l inp k lin hp

  • + p k kiu l xo: Nguyn l hot ng ca loi p k ny l da vo s bin dng n hi ca phn t l xo di tc dng ca p sut. bin dng thng c phng i nh c cu truyn ng phng i v cng c th chuyn i thnh tn hiu truyn i xa + p k kiu pittng: Loi p k ny da vo nguyn l ti trng trc tip: p sut o c so snh vi p sut do trng lng ca pittng v qu cn to ra trn tit din ca pittng . + p k kiu cht lng: Loi p k da vo nguyn l hot ng thu tnh: p sut o c so snh vi sut ca ct cht lng c chiu cao tng ng. V d p k thu ngn, p k ch U, p chn khng, p k bnh hoc p k bnh vi ng nghing c gc nghing c nh hay thay i,+ p k theo nguyn l in: Loi p k ny da vo s thay i tnh cht in ca cc vt liu di tc dng ca p sut. p k da vo s thay i in tr gi l p k in tr hay theo tn ca loi dy dn. V d p k in tr maganin. p k dng hiu ng p in gi l p k in. V d mui sec-nhc, tuamalin, thch anh+ p k lin hp: p k lin hp ngi ta s dng kt hp cc nguyn l khc nhau. V d: mt p k va lm vic theo nguyn l c, va lm vic theo nguyn l in.

  • 3.Theo cp chnh xc:Tt c cc phng tin o p sut dng vo cc mc ch khc nhau u c phn loi theo cp chnh xc. i vi p k l xo hay hin s, cp chnh xc c k hiu bng mt ch s thp phn tng ng vi ln ca gii hn sai s cho php biu th theo phn trm gi tr o ln nht, v d: p k l xo cp chnh xc 2,5, phm vi o 100 bar th sai s cho php l 2,5 bari vi p k pittng hoc cht lng th sai s ny c tnh theo phn trm gi tr ti im o. V d: p k pttng 3DP 50, c phm vi o (1-50) bar, cp chnh xc 0,1, sai s cho php ln nht ti im o 15 bar s l 0,015 bar v ti 50 bar l 0,05 bar.Cp chnh xc ca cc phng tin o p sut c qui nh theo hai dy cp chnh xc sau:0,0005; 0,005; 0,02; 0,05; 0,1; 0,16; 0,20; 0,25; 0,4; 0,5; 1; 1,6; 2,5; 4; 6; v 0,0005; 0,01; 0,02; 0,05; 0,1; 0,2; 0,6; 1; 1,6; 2; 2,5; 4; 6.

  • III. PHNG PHP O P SUT

    PHNG PHP O

    o p sut tnh:

    -o trc tip cht lu thng qua 1 l c khoan trn thnh bnh

    -- o gin tip thng qua o bin dng ca thnh bnh di tc ng ca p sut

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    o p sut ng:

    -Da theo nguyn tc chung l o hiu p sut tng v p sut tnh

    -C th o bng cch t p sut tng ln mng trc, t p sut tnh ln mng sau ca mng o.

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  • o p sut tnh:p sut tnh tng ng vi p sut gy nn khi cht lng khng chuyn ng- o p sut cht lu ly qua mt l c khoan trn thnh bnh nh cm bin thch hp.- o trc tip bin dng ca thnh bnh do p sut gy nn.

  • o p sut ng:p sut ng do cht lu chuyn ng gy nn v c gi tr t l vi bnh phng vn tc cht lu.

    Hnh : o p sut ng bng ng Pitot

  • C th o p sut ng bng cch t p sut tng ln mt trc v p sut tnh ln mt sau ca mt mng o (hnh), nh vy tn hiu do cm bin cung cp chnh l chnh lch gia p sut tng v p sut tnh.

    Hnh:o p sut ng bng mng1) Mng o 2) Phn t p in

  • IV.Cng tc p sutu cp kh voTrc pittongVt chnh cng l xopittongL xo yCng tc 4.1.Cu to

  • 4.2 .Nguyn l hot ng Sc cng ca l xo quyt nh gi tr p sut m cng tc tc ng. Khi cp kh vo u vo cp kh, nu p sut kh nh hn sc cng ca l xo th l xo s khng b nn lc pittong s khng b y, cng tc hnh trnh khng b tc ng. Nu p sut kh ln hn sc cng ca l xo th l xo s b p li , pittong b y li v pha sau lm cho cng tc hnh trnh tc ng. thay i gi tr p sut kh cn tc ng ta dng vt chnh cng ca l xo. Trong thc t ngi ta hay dng cng tc p sut ny trong cc my nn kh cng sut b, n dng ct ngun my nn kh khi p sut theo yu cu.

  • V.Mt s loi cm bin p sutCm bin p sut mng sc co gin kim loiCm bin p sut p in thch anh

  • a. Cu to Vt liu lm mng sc co gin c th l kim loi (trong thc t l hp kim Cu-Ni) hay vt liu bn dn-thng l silic. Di tc dng ca p sut mng sc co gin b bin dng. S thay i in tr ca n gm hai thnh phn: hnh hc v tnh cht vt liu.Cm bin p sut vi mng sc kim loi phn ln da vo s thay i hnh hc dn n s thay i in tr.

  • c. Phn loi:Cm bin p sut chia lm 3 loi tu theo phng php ch to: + + Mng sc co gin l kim loi. + mng sc co gin mng mng. + mng sc co gin mng dy.

  • Mng sc co gin l kim loi Thng l nhng ng dy in bng kim loi rt mn nm trn mt n bng cht do. Ngi ta thc hin bng phng php in la hoc quang khc. V s thay i chiu di thc t rt b, cho nn ng dn in ny c ch to thnh hnh un khc c chiu di kh ln trn mt din tch b, t ta c s thay i in tr ng k.

  • Mng sc co gin mng mng c ch to theo phng php bc hi chn khng hay cng ngh phun bi, vi phng php ny mng sc s cc mng do nhy ca mng cao v t b nh hng ca nhit .Mng sc co gin mng dy c ch to trn nn gm vi k thut in la, loi mng dy c nhy khng cao v chu nhiu nh hng ca nhiu, do trong thc t loi mng y t c s dng.

  • Cm bin p sut p in thch anh

    Hin tng p in: Khi ko dn hoc nn tinh th in mi theo phng php c bit th trn cc mt gii hn ca tinh th xut hin cc in tch tri du.Hin tng c gi l hiu ng p in thun. V ngc li, nu ta p ln 2 mt tinh th mt hiu in th lm cho b mt tinh th b dn hoc nn th l hiu ng p in nghch p in thun p in nghch

  • Cm bin p sut p in thch anhNguyn l: Cm bin p sut p in thch anh(SiO2) lm vic da trn hiu ng p in ca vt liu thch anh Di tc dng ca lc c hc, tm p in b bin dng, lm xut hin trn hai bn cc cc in tch tri du. Hiu in th xut hin gia hai bn cc (V) t l vi lc tc dng (F).

  • Ty theo hng tc dng ca lc i vi tinh th thch anh m ta c cm bin p in thch anh theo hiu ng chiu di hoc hiu ng ngang. Hiu ng theo chiu di:

  • Vi hiu ng chiu di s lng in tch pht sinh khng ph thuc vo kch thc hnh hc ca tinh th m ch ph thuc vo lc. Nh th tng s lng in tch, ngi ta t nhiu phin mng tinh th thch anh ni tip nhau v lc v v mt in c ni song song vi nhau.

  • Hiu ng ngang

    Hiu ng ngang s lng in tch ph thuc vo kch thc hnh hc. Cm bin p in thch anh ngy nay hu ht l da vo hiu ng ngang

  • c im v ng dng. Ta c th coi tinh th thch anh nh mt t in, nh chng ta bit sau khi np in th t in phng in dn theo thi gian, thi gian phng in nhanh hay chm ph thuc vo in tr phng in. i vi tinh th thch anh in tr phng in l in tr cch in. Nh vy khi s dng cm bin p sut tinh th thch anh phi lu l sau khi lc tc ng nu khng thc hin ngay php o th cng lu sai s ca php o cng ln.

  • Trong thc t ngi ta cho php cm bin psut tinh th thch anh lm vic ti nhit 2400C. V nu ta cho cm bin lm vic nhit cao th tinh th thch anh s b mt i hiu ng p in. Di p sut tnh tinh th thch anh khng xy ra hiu ng p in. Do o c p sut cn phi bin p sut thnh lc bng mt mng mng. Cc cm bin o p sut tinh th thch anh thc t dng o p sut ti 250 bar.

  • n v tinh th thch anh cc k n nh c v mt ha hc v vt l. Nh c s n nh tn s c bit , thch anh c s dng trong cc thit b in t, truyn thng nh in thoi di ng, cc ng dng khng dy cng nh cc thit b tiu dng nh tivi, u video, my nh k thut s v my tnh, cung cp chnh xc tn hiu c lin quan x l mt lng ln thng tin nhanh chng v ng nht. Hn na, thch anh c s dng rng ri nh l mt ngun nguyn liu ca ng h yu cu chnh xc cao nh ng h eo tay, ng h bm gi

  • VI.ng dng thc t:

  • ***

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