Lecture_18_Part2

# Lecture_18_Part2 - Ammeters Voltmeters and Ohmmeters Ammeter measures current I Voltmeter measures voltage difference V Ohmmeter measures

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Ammeter: measures current I Voltmeter: measures voltage difference Δ V Ohmmeter: measures resistance R Ammeters, Voltmeters and Ohmmeters

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0.150 Connecting ammeter: Conventional current must flow into the ‘+’ terminal and emerge from the ‘-’ terminal to result in positive reading. Using an Ammeter
Simple ammeter using your lab kit: Simple commercial ammeter Digital ammeters: uses semiconductor elements. ADC – analog-to-digital converter (Combination of comparator and DAC) Ammeter Design

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Ammeter is inserted in series into a circuit – measured current flows through it. R emf A Process of measuring requires charges to do some work: Internal resistance r int 0 = RI emf No ammeter: R emf I = With ammeter: 0 int = RI I r emf int r R emf I + = Internal resistance of an ammeter must be very small Ammeter Design: r int
R emf r int A R shunt I a I shunt I 0 int = shunt shunt a I R I r shunt a I I I + = ( ) 0 int = a shunt a I I R I r ( ) 0 int = + I R R r I shunt shunt a I R r R I shunt shunt a + = int

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## This note was uploaded on 04/02/2008 for the course PHYS 272 taught by Professor K during the Winter '07 term at Purdue University-West Lafayette.

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Lecture_18_Part2 - Ammeters Voltmeters and Ohmmeters Ammeter measures current I Voltmeter measures voltage difference V Ohmmeter measures

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