USING OWER CSS WEIGHTS TO CORRECT ND CHECK THE NONINERITY OF BNCES Tiohy Chnglin Wng, Qiho Yun, hu Reichuh Mele-Toledo Insuens Shnghi Co. d, Shnghi, P R Chin Mele-Toledo GH, Geifensee, Swizelnd BSTRCT ny eleconic lnce hs oe o less nonlineiy. This ppe pesens ehod o coec nd check he nonlineiy y using wo ses of lowe clss weighs. Soe of he key cuses of he nonline eo e descied fis. Coon-ee pol nonline pen wee sudied in deil. coecing pocedue, using se of lowe clss o even no clss weighs is hen descied. The coecing coefficien is given in he ppe in n ppen fo. Siulion nd es esuls showed he nonline eo educed diclly wih he ehod. check pocess is equied efoe lnce goes o he ke o es whehe he finl nonlineiy is wihin he olence. check pocedue, nely diffeenil ehod, is pesened. The ehod is ccue enough y using second se of lowe clss weighs. ow cos, high efficiency nd good quliy cn e chieved in lnce poducion y using he ehod pesened.. INTRODUCTION The lineiy descies how well lnce is le o follow he line elion eween he lod nd he disply vlue of he lnce. The idel chceisic weighing cuve is sigh line eween he zeo nd iu lods. The nonlineiy defines he iu posiive o negive deviion of he displyed vlue fo h of he idel chceisic of sigh line. Evey eleconic lnce shows oe o less nonlineiy. The key cuses of nonlineiy e descied elow.. Mechnicl defoion The secion e of he elsic e in sin guge ype lnce chnges when he lod chnges. This will cuse he nonline elionship eween he lod nd he sin poduced. The level e in n MFR gneic foce esoion ype of lnces will defo when lod dded. Then he io of he e will chnge. This will lso cuse nonlineiy.. Eleconic The oupu of he idge in sin guge lod cell is heoeiclly no line wih he sin fel. In cse he idge is no syeic, o he lod is oo lge, he nonline eo will incese. The d coon ode ejecion of copo y cuse nonlineiy in PWM eled /D convee, s he ejecion io is eled, u no linely eled o he coon ode inpu, which is popoionl o he lod usully. Woking poin eled un on/un off ie dely of nsiso will influence he PWM esuls. Thee is phse dely if he end poin ipednce of he signl nsiing line eween he lod cell nd he /D convee does no ch wih he line ipednce. This phse dely will vy, u no linely vy wih lod chnges, nd will cuse nonlineiy.. Mgneic The copension foce is supposed o e linely eled wih he cuen in he coil, which is loced in gneic field in n MFR ype of lnces. Howeve, s he cuen will influence he gneic field, hei ecions will cuse oe o less nonlineiy in lnce.
In pcice, he nonline chceisic o he nonline pen of coecly designed nd popely nufcued lnce should e elively sle. I should hve no disconinuiies in he woking nge nd he pen should e s siple s pol efoe coecion [. Figue shows he esul of coecly designed nd popely nufcued lnce efoe nonlineiy coecion. Wih oden eleconic lnce, his nonline eo is usully coeced y he sofwe efoe he vlue is displyed. I will ipove he pefonce diclly o use pol coecion, o -poin lineizion, s descied in his ppe. Figue howeve, shows he nonline chceisic of dly designed lnce odel efoe coecion. Wih his pen, -poin coecion will no wok popely. nonline eo, g - - -.5 - -.5 - -.5 od, g 5 5 nonline eo, g.5.5-5 5 lod, g Figue : Coecly designed lnce efoe coecion Figue : Bdly-designed lnce odel efoe coecion. INERISTION y y, y y y od Figue : -poins lineizion Pocedue Zeo od:, /D ou: / od, fis:, /D ou: Full lod:, /D ou: / od, second:, /D ou: We define he elive lod s:
ssuing he pol pen of nonlineiy, [ N 5 Whee, N is he iniil nonline eo in he hlf lod eween nd. e 6 [ N 7 If,, hen [ N 8 [ N 9 s, one cn find, e he coecing foul e pol lso: [ [ y e, y u Then, [ u If y u nd le u, o deeine 5
y [ 6 Siilly, we ssue y u 7 nd le u, o deeine, 8 y [ 9 To ke he soluion syey, le / y [, o y c c c Whee, he coecing coefficien, B c c B c B, nd, B 5 One cn find he coecing coefficien cn e oined in n ppen fo. The pocedue is vey ccue if he nonline pen is pol. n iniil nonline eo of pp fo - % o % full lod fo eple in Figue, even if, nd e no ccue ll, such s.,.7, % full lod, -8% full lod, he iu finl nonline eo fe coecion will heoeiclly e less hn.6 pp fo -% o % full lod, s Figue 5 shows. Nonline Eo Coeced, pp.8. -5% % 5% % 5% -. -.8 Nonline Eo Iniil, pp 5 5-5% % 5% % 5% -5 - od od Figue : Iniil nonline eo, eple Figue 5: Nonline eo fe coecion In cse he geed nonline eo fe coecion is pp, clculion esuls show h he iniil nonline eo should no e lge hn pp. The pocedue is ecellen fo using lowe clss, o even no clss weighs o cy ou he lineizion. fe he coecion, one cn find, hee is no eo when he lod is, /, nd. So he ehod is clled -poins lineizion. I is esy o esie he iniil nonline eo wih elow foul, if is close o, nd - is close o he full lod.
N 6 Foul 6 cn lso e used y he end use o esie he pefonce of lnce. Pciclly, o ge he es esul, he iniil nonline eo should no e lge hn pp if he equieen of he finl eo is pp. - should e s lge s possile he full lod. should no e less hn., no gee hn.7 he es is, close o he zeo lod is he es.. NONINERITY CHECK fe he coecion, check pocedue us e followed in lnce poducion o see whehe he pen ssued o e ccue enough, o o check whehe he nonline eo in he whole weighing nge is wihin he specificion fe he coecion enioned. fe -poins lineizion, hee e les hee lod poins fo he lnce wihou nonline eo s enioned ove. I is esonle o ssue h he nonline pen fe such lineizion is cuicl pol pssing hough he ned poins. NN*.785**-*- 7 Whee N in pp is he iu nonline eo when., o.7887. The cuve showed on Figue 6 is he sid pen. The pocedue is o design es, o esie he iu nonline eo, nd see whehe i is wihin he specified olence, pp fo eple. Theoeiclly, his sk cn e done y using se of known weighs. Bu he pocess is cosly nd low efficien, o even ipossile in soe cses. We cn design 5-segen check pocedue ccoding o he diffeenil ehod y using se of 5 weighs W W5, ech of which is ppoiely % of he full lod, nd use he fis one s he efeence weigh WW.. % lod, disply Z. % lod: W, disply Z. % lod: W, disply Z. % lod: WW, disply Z 5. % lod: WW, disply Z5 6. 6% lod: WWW, disply Z6 7. 6% lod: WWW, disply Z7 8. 8% lod: WWWW, disply Z8 9. 8% lod: WWWW5, disply Z9. % lod: WWWW5W, disply Z Then clcule he diffeence o he segen incese coesponding o W: DZ-Z 8 DZ-Z 9 DZ6-Z5 DZ8-Z7 D5Z-Z9 The nonline cuve cn e esied s N nd iu nonline eo, i D vege D i 5 i i 5
5 Di in Di i i N k * 5 Whee k. kes heoeiclly he foul fi. The wo oldfce ows in Figue 6 epesen he Di-vegeDi, nd indi-vegedi. Sensiiviy sudy shows, even if Wi is % full lod - 5%, k. is sfe enough. Nonline eo, pp.75 od - % - % % 6% 8% % -.75 - Figue 6: 5-segen nonlineiy check One y conside sine nonline cuve ohe hn he cuicl pol pen. Th is o ssue: NN* sin π* 5 The iu nonlineiy eo occus when o.75, hen -segens nonline check using weighs ech 5% full lod ppoiely y e used nd k.. If 5- segens check is doped ny wy, k.9 will e good enough. Wheve cuicl pol o sine pen, we need use in ll cses k. fo 5-segens check pocedue in foul. The esul is owds oe sfe diecion. The weighs need no e ccue, even no clss weighs e OK. Fo nlyicl lnces, he weighs wih olence of 5% e good enough in os cses. The copison wih ohe ehod sed on he diionl nonlineiy definiion showed, h he poduc quliy of lineiy eled ws guneed wih he pesened ehod. he se ie he ehod is low cos, high efficien in he poducion. Duing he design phse howeve, i is equied o do uch oe es o pove h he nonline pen pesued is ccue enough. REFERENCES [ hu Reichuh: Non-ineiy Of ooy Blnces nd Is Ipc On Unceiny. NCS Wokshop nd Confeence, Toono, Cnd, July 7-. [ Heinz Ruishuse, hu Reichuh: The New METTER T nlyicl Blnce. Mele Toledo Copny Pulicion 988 ME-778 ddess of he uhos: Tiohy Chnglin Wng, Mele-Toledo Insuens Shnghi Co. d, 589 Gui Ping Rod, Shnghi, P R Chin. Tiohy.wng@.co Qiho Yun & hu Reichuh, Mele-Toledo GH, I ngche, P.O Bo Tec CH-866 Geifensee, Swizelnd. qiho.yun@.co & hu.eichuh@.co 6