Programmed Review for Electrical Engineering, Third Edition
This text contains an organized review of the basic electrical engineering fundamentals, with 111 problems, solutions and explanations for the core electrical engineering concepts.
TABLE OF CONTENTS Programmed Review for Electrical Engineering, Third Edition
Voltmeters
This problem illustrates the practical application of using a microammeter and some precision resistors to create a voltmeter.
Problem 2-14: VOLTMETER DESIGN
Q:
Given a microammeter having a 50 ? amp movement and an internal resistance of 10 ohms, design a voltmeter with ranges of 10 VDC, 50 VDC, 100 VDC, and 500 VDC.
Answers
Q:
The voltmeter circuit is as follows:
A 50 ? amp movement yields a sensitivity of:
Calculating the precision resistors:
Resistance of the 10 volt range, R 10, is:
(answer)
R 10 = R 4 + R M = (10 volts) (20,000 ?/volt) = 200,000 ?
R 4 = 200,000 - 10 = 199,990 ?
Resistance of the 50 volt range, R 50, is:
(answer)
R 50 = R 3 + R 10 = (50 volts) (20,000 ?/volt) = 1 M ?
R 3 = 10 6 - 200,000 = 800,000 ?
Resistance of the 100 volt range, R 100, is:
(answer)
R 100 = R 2 + R 50 = (100 volts) (20,000 ?/volt) = 2 M ?
R 2 = 2 10 6 - 10 6 = 1 M ?
Resistance of the 500 volt range, R 500, is:
(answer)
R 500 = R 1 + R 100 = (500 volts) (20,000 ?/volt) = 10 M ?
R 1 = 10 ...
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