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Unformatted text preview: lt iplier. One way
is t o det ermine t ot al c irc uit resist anc e using Ohm's Law in t he "t ot al" c olumn (R=E/I),
t hen subt rac t t he 500 Ω of t he movement t o arrive at t he value f or t he mult iplier: http://www.allaboutcir cuits.com/vol_1/chpt_8/2.html 2/6 1/22/2014 Voltmeter desig n : Dc M eter ing Cir cuits Anot her way t o f igure t he same value of resist anc e would be t o det ermine volt age drop
ac ross t he movement at f ull- sc ale def lec t ion (E=IR), t hen subt rac t t hat volt age drop
f rom t he t ot al t o arrive at t he volt age ac ross t he mult iplier resist or. F inally, Ohm's Law
c ould be used again t o det ermine resist anc e (R=E/I) f or t he mult iplier: Eit her way provides t he same answer (9.5 kΩ), and one met hod c ould be used as
verif ic at ion f or t he ot her, t o c hec k ac c urac y of work. Wit h exac t ly 10 volt s applied bet ween t he met er t est leads (f rom some bat t ery or
prec ision power supply), t here will be exac t ly 1 mA of c urrent t hrough t he met er
movement , as rest ric t ed by t he "mult iplier" resist or and t he movement 's own int ernal
resist anc e. Exac t ly 1/2 volt will be dropped ac ross t he resist anc e of t he movement 's
wire c oil, and t he needle will be point ing prec isely at f ull- sc ale. Having re- labeled t he
sc ale t o read f rom 0 t o 10 V (inst ead of 0 t o 1 mA), anyone viewing t he sc ale will
int erpret it s indic at ion as t en volt s. Please t ake not e t hat t he met er user does not have
t o be aware at all t hat t he movement it self is ac t ually measuring just a f rac t ion of t hat
t en volt s f...
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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