Nguyen Ly Do Muc 5191

7/31/2019 Nguyen Ly Do Muc 5191

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Nguyn l o mc, lu lng, psut,...

Chng ta dng rt nhiu cc thit b o, nhng chng ta hiu g v nguyn l o c cc i lng . Hy cng chia s. Ti xin post bi nguyn lo mc m u.K thut o mcVt liu: c bn loi vt liu : cht rn, cht lng, cht st, mt cch ly.Phng php o : c nhiu phng php o mc : thi bt kh, chnh p, olc cng, phao ni, cng tc khong h, loadcell, dn in, ht nhn,radar, RF Admittance, siu m, sng viba, .

Kiu o: o lin tc v o im.Nhng tc nhn ca qu trnh o lng nh hng n chnh xc: p sut,nhit , cnh khuy, cht n mn, bt ni, mi trng nguy him v mc c hi ca ho cht.

Nhng tc nhn nh hng khi thay i v vt liu: t trng, thnh phn hohc, vt liu bm dnh, c tnh v in, V khng c k thut no l hon ho cho mi ng dng.Ch c khi nim ci ny hay hn ci kia m thi.Thi bt kh: r, n gin, d lp. hin th mc lin tc, ch o c chtlng.

dn in: r, n gin hn loi trn, khng c b phn di chuyn, oim, dng cho cht lng dn in, d b nh hng bi lp vt liu bmdnh trn in cc.Chnh p: thng dng, o lin tc, gi hp l, d lp t nhng th phncng ngy cng gim. D b nh hng bi t trng ca vt liu, khng phhp khi o cc cht lng c dng ht, khong o nh rt kh s dng, c

bit lu n s n mn ca ho cht.Displacer: o mc lin tc mt cch ly, gii hn mc dch chuyn, rt t cc

phn t dao ng. Khi t trng thay i phi hiu chun li. Khi b bm dnh

phi b u vo, khng tt lm trong ng dng o mc c cnh khuy. Khidi o tng ln th ph u t cng tng ln ng k.Cng tc khong h: cu trc n gin, d lp, chng c s nh hngca bt kh. ch dng pht hin mc dng im, gii hn v mc nhit .Phao : Phng php ny khng gii hn v mc cao ca bn, chnh xckhng cao, ph u t thp nu khng c phn hin th t xa, gii hn vmc p sut lm vic. Cho kt qu o lin tc & o im. Khi o im c


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th o c c mt cch ly. i vi cht lng st +ht l khng ph hp,cnh khuy cng nh hng n chnh xc.Loadcell: o khi lng, tin dng cho hu ht cc vt liu cha trn silo.d nh hng bi , bng tuyt cng nh sc gi.RF Admittance: k thut mi cho vic o im cng nh lin tc, di p sutnhit lm vic rng, o c mi cht liu. Khi hng s in mi ca vtliu thay i dn n vic thay i cm bin v b truyn ph hp. Khng bnh hng bi s bm dnh trn cm bin.Ht nhn: o khng tip xc, lp bn ngoi bn cn o mc. Ph hp vimi trng nhit p sut cao, vt liu n mn. Gi cc cao, khi s dng

phi c giy php s dng, chng nhn v kim tra. Kh nng r r phng xcng l iu ngi s dng rt e ngiSiu m: K thut o lin tc khng tip xc, khng c phn t dch chuyn.

Nhy cm v v tr hn cc k thut khc. nh hng bi hi nc, bt kh,

di nhit v p sut lm vic khng cao cng nh cu trc bn trong bnb. Khng th hot ng trong mi trng chn khng.Radar: o mc lin tc vi chnh xc cao. b qua hi nc. iu kinlm vic gii hn bi di p sut lm vic thp. C th o c mc mtcch ly.

Cc cch o mc cht lng v nguyn l lm vic

Nhu cu v nhng h thng t ng ha x l tinh vi, s nghim ngt canhng quy chun trong iu khin qu trnh, v nhng yu cu ngy cngkht khe trong mi trng o mc khin k s qu trnh phi i tm nhngh thng o mc tin cy hn, chnh xc hn. Kt qu o chnh xc cao hnlm gim thiu nhng kh nng sai lch trong qu trnh x l ha cht (cp trong bi vit ny l ho cht dng lng), nng cao cht lng ca sn

phm u ra, gim chi ph v lng ph.Nhng cng ngh o mc tin tin hin nay c th gip cc k s d dngtm c thit b ng , p ng c nhng yu cu nu trn.

S giao thi trong cng ngh o mc

Thit b o mc n gin v c nht trong cng nghip l mt loi bnhtrong sut. L phng php o th cng truyn thng v n c nhiu hnch: vt liu ca thit b c th b n mn, chu s tc ng ca mi trng;con ngi phi tip xc trc tip vi mi trng o; c th xy ra tnh trngchy, n d r r cht lng qua np, v cn ca cht lng c th hn ch tmnhn. Do c qu nhiu hn ch, nn thit b ny nhanh chng b cc thit bcng ngh tin tin hn thay th.


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Mt thit b o mc khc da vo trng lc, l thc o kiu phao. Mtchic phao n gin c th ni trn b mt cht lu. Chic phao ny chus tc ng t lc ca cht lu v khng kh pha trn lm n ni trn b mtv dao ng theo mc cht lu. Bn cnh , mt thit b khc cng c sdng rng ri xc nh mc cht lu l u o thy tnh.

Trn y l nhng thit b o mc n gin, quen thuc vi ngi sdng. Nhng khi xut hin nhng nguyn tc v ng dng o mc tr nn

phc tp hn, th y l lc ngnh cng nghip o mc chuyn mnh vi sra i ca nhng cng ngh mi s dng my tnh tnh ton. Khi cngngh o mc gn vi cng ngh my tnh th d liu t cm bin truyn vh thng iu khin v gim st phi dng my c th c c. Trong ,nhng dng tn hiu u ra hu dng l dng tn hiu dng in mch vng

(current loops), in p tng t (analog voltages), v tn hiu s (digitalsignals). Tn hiu in p tng t l dng tn hiu d thit lp v gii m,tuy nhin n li d b nh hng bi ting n v yu t ngoi vi khc. Tnhiu in mch vng 4-20 mA l dng tn hiu thng dng ngy nay. Dngtn hiu ny c th truyn khong cch xa m t b suy hao. Dng tn hius c m ha di dng nghi thc bt k (nh Foundation Fieldbus, Hart,Honeywell DE, Profibus, and RS-232) l dng tn hiu khe nht. Tuynhin, i vi nhng cng ngh c nh RS-232 th tn hiu s ch c thc truyn khong cch nht nh. Cn i vi cng ngh khng dy mith tn hiu di dng s c th truyn c khong cch xa hn nhiu mhu nh khng nh hng g n cht lng tn hiu truyn.

Khi cng xut hin nhng cng ngh o tin tin (nh siu m, ra a, laze)th dng tn hiu m ha cng cng tinh vi hn, i hi phi c my tnh sthng minh nh dng m tn hiu. Cng vi l nhu cu lin lc tintin v h thng nh dng s cho chng ta nhng li gii thch v xu hngtin ti s dng my tnh vi x l nhng trong hu ht nhng thit b o mc(hnh 1).

Nhng cng ngh o mc "trng thnh"

Trong bi vit ny chng ta coi m c ca kh khong trng trongbnh l khng ng k so vi m c ca cht lu cn o. Ngoi ra,cng coi cht lu cn o trong bnh cha ch l mt loi duy nht, bt bin.


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Mt s trong nhng cng ngh o mc c th dng o a mc, trong c 2 hay nhiu loi cht lng khc nhau trong cng mt bnh cha.

- Phao. Phao c nguyn l lm vic rt n gin. Phao l mt vt ni t trnmt nc do trng lc ca cht lng v khng kh pha trn tc ng. theo di mc dao ng ca cht lng, ta gn mt thit b c kh vi phao.

Nhng h thng phao u tin s dng cc thit b c kh nh dy cp,thc dy, rng rc v bnh rng theo di mc dao ng ca cht lng.

Nhng kiu o ny cho chnh xc khng cao. Ngy nay, mt loi phaoph dng l phao t.

Nhng b pht tn hiu mc u tin i km vi phao l nhng thit b chotn hiu tng t hoc ri rc s dng mt mng thit b in tr v b

chuyn mch nhiu li g. Do cho gi tr o ri rc, nn gi tr o gia ccbc tn hiu b b qua.

- Thit b thy tnh. ng thy, phng php o bng bong bng v b phttn hiu p sut vi sai u c gi l thit b o thy tnh.

ng thy hot ng da trn nh lut c-si-mt. Nh trong hnh 2 ta thy,ng thy c nhng trong cht lu. Cht lu trong ng thy m c hn ngoi bnh cha. Khi cht lu trong bnh cha dng th cht lu trong ngthy cng dng tng ng. Mc cht lu trong ng thy thay i s to ramt p lc, v mt b chuyn i ni vi b pht tn hiu lm nhim vkim sot s thay i p lc . Qua ta bit c s thay i mc chtlu trong bnh cha.

Cm bin mc kiu bong bng (hnh 3) c 1 ng dn kh xung y bnh

cha to bong bng. Khi kh c dn vo, p sut trong ng s tng chon khi thng c p sut ca cht lng trong bnh. Mt b chuyn ic ni vi ng dn kh gim st s tng p trong ng. T p sut oc s tnh ra mc cht lng trong bnh cha.


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Cm bin p sut vi sai c m t nh trong hnh 4. Loi cm bin ny omc bng cch o chnh lch p sut tng y bnh cha v p suttnh hay cn gi l p sut ca khong khng kh trong bnh cha tnh ramc ca cht lng. Loi cm bin ny ly khng kh bn ngoi lm thamchiu. Nh trong hnh 4 ta thy, trn nc bnh cha c mt l thng khnhm cn bng khng kh trong bnh cha v khng kh mi trng bnngoi. Khng ging nh cm bin o mc bng bong bng kh, cm bin psut vi sai c th s dng trong mi trng nn p.

- Loadcell (cu in tr o p lc). Loadcell hay thc o bin dng/cuin tr o p lc l mt loi gi c kh c trang b mt hay nhiu cm

bin o lch/nghing ca gi . Khi lc tc ng vo loadcell thay ilm cho gi cng thay i theo v to ra tn hiu u ra tng ng. Ccloadcell c thit k ph hp vi mi kch c thit b (t thit b nh c

trng lng vi gam n thit b c trong lng tnh bng tn).

Loadcell o mc bng cch chuyn i trng lc ca cht lng tc ng nnn thnh tn hiu c th c c. Khi mc cht lng trong bnh cha tng,th lc tc ng ln loadcell cng tng v ngc li. Li th ca loadcell lo khng tip xc vi cht lng nn n c s dng rng ri trong nhiung dng khc nhau, nhng nhc im ca n l gi thnh cao v tnh nng

b gim nhanh chng theo thi gian.

- Thc o mc t tnh

Thc o mc t tnh (hnh 5) c ly lm vt thay th cho phng phpo bng bnh trong sut. Thc o t tnh c nguyn l o ging nh phao,nhng c im khc l chng xc nh mc bng t tnh. Mt chic phao ttnh t trong ng ph gn thng 2 u vi bnh cha. Do vy, khi mc chtlng trong bnh cha tng th mc cht lng trong ng ph cng s tngtng ng hoc ngc li. V phao t tnh trong ng ph cng dng ln

hoc h xung tng ng theo mc cht lng trong ng ph. Mt conthoi/mn hnh hin th chuyn ng theo phao t tnh, do vy ta xc nhc mc cht lng. Thc o t tnh ch hot ng c khi ng ph clm bng vt liu khng hp th t tnh. Thc o t tnh c th c sdng nhng ni c nhit , p sut cao, hay trong nhng cht lng nmn.


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- Cm bin o mc bng in dung

Cm bin mc in dung (hnh 6) hot ng da trn s khc bit hng sin mi gia cht lu v khng kh. iu kin cn thit p dng phng

php ny l hng s in mi ca cht lu phi ln hn hng s in mica khng kh, thng l gp i. Hng s in mi ca khng kh lkhong 1.0; du c hng s in mi t 1,8 n 5; nc c hng s in mi gia khong 50 n 80. Khi mc cht lu thay i th hng s in micng thay i tng ng. Mt loi t in c gi l cu in dung o ton

b in dung v cho tn hiu o lin tc.

Nhng cng ngh mi ni

C l s khc bit ln nht gia cng ngh o mc tn hiu lin tc trcy v by gi l thi gian cho kt qu tn hiu o. Nhng thit b o mic trang b cng ngh hin i ngy nay cho kt qu o bng cch okhong cch gia cht lu v im t cm bin hoc b truyn tn hiu tinc bnh cha. Nhng thit b ny pht ra mt sng xung xuyn qua lpkhng kh hoc cht dn trong bnh, gp b mt cht lu v di ngc tr licm bin. Mt mch in nh thi trong cm bin o tng thi gian sngxung phi di chuyn, chia i, v sau tnh ra mc ca cht lu. Nhngcng ngh mi qua th nghim v c chp nhn rng ri l sng sium, sng vi ba (ra-a) v nh sng.

- Cm bin mc t gio. T gio l cng ngh qua thc t kim nghimv c cng nhn l phng php c v tr phao c chnh xc cao.Khng ging nh thit b c kh, b truyn tn hiu t gio ly tc cadng sng xon chy dc theo dy dn pht hin ra v tr ca phao.

Trong cu trc ca mt cm bin mc t gio (hnh 7), mt chic phao cgn cc thanh nam chm vnh cu. Dy cm bin c ni vi mt cm binmng gm p in, ng dn ca cm bin chy xuyn qua l ca phao.

xc nh v tr ca phao, b truyn tn hiu pht i mt xung in ngndc theo dy cm bin to nn mt mi trng in t bao quanh chiu didy dn. ng thi mch in nh thi cng c kch hot cng lc. T


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trng ca dy dn ngay lp tc tng tc vi t trng do nam chm gntrn phao sinh ra. Kt qu l mt lc xon c sinh ra dc theo dy dn.Lc ny b di ngc tr li cm bin mng gm p in. Khi cm bin cmnhn c lc ny, s sinh ra mt tn hiu in dng hot ng ca mchin nh thi. Mch in nh thi o khong thi gian t lc pht tn hiuxung in cho ti lc cm bin nhn c tn hiu phn hi. T nhng thngtin thu c, v tr ca phao c xc nh chnh xc v c hin th didng tn hiu mc. Li ch ca cng ngh ny l tc tn hiu xc nhc v bt bin trong nhng ng dng o nh nhit v p sut. Ngoira, tn hiu ca cng ngh ny khng b nh hng bi bt bong bng, ccchm tia sng hay m thanh. Mt li ch khc l ch c phao l thit b duynht phi chuyn ng tng ng vi b mt cht lu.

- Cm bin mc sng siu m. C nguyn l o gn ging nh cm bin tgio, cm bin mc sng siu m (hnh 8) xc nh mc bng cch okhong thi gian t lc truyn sng ti lc nhn c sng phn hi. Khcvi cm bin t gio, cm bin mc sng siu m s dng sng di tn s10 KHz. Tc truyn ca sng (340m/giy trong khng kh 15 C) phthuc vo loi kh v nhit ca kh bn trong bnh cha.

Cm bin mc tia laze. c thit k o dng cht rn, dung dch c nhdu nht, sa... cm bin mc tia laze c nguyn l hot ng n gin,tng t nguyn l hot ng ca cm bin o mc sng siu m. Nhngthay v dng tc ca m thanh xc nh mc cht lu, loi cm binny dng tc ca nh sng xc nh mc (hnh 9).

Cm bin laze c t trn nc bnh cha pht mt tia laze xung b mtcht lu. Tia ny b di ngc li ti b pht hin ca cm bin. Mch innh thi o thi gian i ca tia sng v tnh ton ra mc ca cht lu. Li

th ca tia laze l khng b phn tn, khng b nh hng bi m thanh vc truyn thng qua khng kh.

Phng php o bng tia laze c chnh xc cao, ngay c trong iu kinmi trng hi nc hay bt bng, v c khong cch o ln n 450m. yl phng php l tng trong nhng bnh cha c nhiu vt cn. i vinhng ng dng c p sut v nhit cao nh trong l phn ng ht nhn


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th laze l phng php la chn hng u.

- Cm bin mc raa. Cm bin mc raa s dng ng ten t trn nc bnhcha pht ra nhng chm sng viba xung b mt cht lu, v mch innh thi lm nhim v tnh ton khong cch t u ng ten ti b mt chtlu da vo thi gian di chuyn ca sng viba t lc pht i ti lc nhnc. phng php ny, nu hng s in mi ca cht lu thp c th nhhng ti cht lng ca kt qu o, v lng nng lng sng phn hi phthuc vo hng s in mi ca cht lu. Nu hng s in mi thp, sngviba (raa) s b hp th vo dung dch hoc i xuyn qua.

Sng viba (raa) cng b phn tn ging nh sng siu m trong cm binsng siu m. Thnh bnh cha, cn bm vo ng ten, hay cc vt cn cngc th gy ra tn hiu sai lch cho cm bin. khc phc nhc im ny,

nhng thut ton phc tp s dng logic m c tch hp cho b pht tnhiu. Nhng nu nh vy li xy ra mt kh khn khc l vic lp trnhtr nn phc tp v phi thay i theo tng mi trng.

Mt gii php c coi l cu tr li cho nhng kh khn trn l mt loicm bin raa dn sng (hnh 10). Mt ng dn sng lm bng vt liu cnghay mt dy ng ten lm thit b dn sng viba t nc bnh cha xung bmt cht lu v a tn hiu v b nhn. Phng php ny t ra hiu qu hnnhiu so vi phng php trc. Sng viba khng b nh hng bi vt cn,nhit hay p sut. Ngoi ra, n cn linh hot trong lp t, c th lp ttheo chiu ngang hay dc u c.

Thay li kt

Chng ta va im qua cc cch o mc t n gin n hin i. Qua cho thy c xu hng pht trin ca cm bin o mc. Cng ngh s angtip sc cho cm bin o mc ni ring v cm bin ni chung, lm cho

chng tr nn thn thin hn, d lp t hn v c chi ph thp hn. Nhnggiao din lin lc tin tin gip truyn ti d liu ca cm bin ti h iukhin v/hoc h thng thng tin ti cng ty tr nn n gin hn.

Cm bin mc ngy ny c lm t nhiu loi vt liu chu ng trongnhng mi trng khc nghit nh du, axt, nhit v p sut cao. Nhngvt liu mi gip cm bin mc c th thm nhp vo hu ht mi ng dng.


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Xu hng ngy nay l thay th nhng thit b c kh v p sut bng nhngthit b o khong cch ti b mt cht lu bng phng php o nh thi.Cm bin t gio, sng siu m, raa v laze l nhng cng ngh a nngang to nn s chuyn mnh mnh m trong cng ngh o mc.

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Nguyen Ly Do Muc 5191