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Unformatted text preview: rom t he ext ernal sourc e. All t hat mat t ers t o t he user is t hat t he c irc uit as a
http://www.allaboutcir cuits.com/vol_1/chpt_8/2.html 3/6 1/22/2014 Voltmeter desig n : Dc M eter ing Cir cuits whole f unc t ions t o ac c urat ely display t he t ot al, applied volt age.
T his is how prac t ic al elec t ric al met ers are designed and used: a sensit ive met er
movement is built t o operat e wit h as lit t le volt age and c urrent as possible f or maximum
sensit ivit y, t hen it is "f ooled" by some sort of divider c irc uit built of prec ision resist ors so
t hat it indic at es f ull- sc ale when a muc h larger volt age or c urrent is impressed on t he
c irc uit as a whole. We have examined t he design of a simple volt met er here. Ammet ers
f ollow t he same general rule, exc ept t hat parallel- c onnec t ed "shunt " resist ors are used
t o c reat e a c ur r ent divider c irc uit as opposed t o t he series- c onnec t ed volt age divider
"mult iplier" resist ors used f or volt met er designs.
Generally, it is usef ul t o have mult iple ranges est ablished f or an elec t romec hanic al met er
suc h as t his, allowing it t o read a broad range of volt ages wit h a single movement
mec hanism. T his is ac c omplished t hrough t he use of a mult i- pole swit c h and several
mult iplier resist ors, eac h one sized f or a part ic ular volt age range: T he f ive- posit ion swit c h makes c ont ac t wit h only one resist or at a t ime. In t he bot t om
(f ull c loc kwise) posit ion, it makes c ont ac t wit h...
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This lab report was uploaded on 04/05/2014 for the course ECSE 291 taught by Professor N/a during the Winter '11 term at McGill.
- Winter '11