RICHLAND COLLEGE
School of
Engineering Business & Technology
Rev. 0 – W. Slonecker
Rev. 1 (8/26/2012)– J. Bradbury
Rev. 2 (3/13/2015)– J. Bradbury
INTC 1307
Instrumentation Test Equipment
Assignment 5
Unit 5 Assignment
For this assignment, use your own paper to show solutions. Bridges should be drawn in the form shown to the right. For each problem, draw the schematic, label the parts, show your formulas and calculations.
Underline your final answers.
NO WORK, NO CREDIT
Name _____________________________________
1. Your balanced bridge circuit has:
R1 = 400  , R2 = 4k  , R3 = 5k 
What is R4?
2. You are required to build a bridge using a 60v power supply. R1 = 1k  , R2 = 5k  , Ra is a pot set to 3k  when the bridge is balanced. You calculate Rb to be __________ ohms. The detector is a galvanometer with an internal resistance of 100  . When nulled, the galvanometer has
_________ volts across it and _________ mA through it.
3. You ask your lab partner to duplicate the bridge in problem 2 using a voltmeter instead of a galvanometer. He mistakenly installs a 3k  resistor for Rb. The voltmeter has an impedance of
9M  with its + terminal at Point 1 and its  terminal at Point 2.
Besides following all the page instructions, calculate the voltage reading on the meter and the current through the meter.
4. In problem 3, your lab partner decides the problem is caused by the voltmeter and replaces it with the original galvanometer. Thevenize the bridge and determine the voltage across the galvanometer and the current through it.
Page 1 of 2

5. You have a circuit of two parallel wires, each
1000’ long in a cable. The Murry Loop is balanced when R1 = 200  , R3 = 300  ,
R2 = RX = 80  (LX resistance)
If the wire resistance is 0.1
 /ft., calculate the LX length to the fault.
Use the LX equation on page 7 of Unit 5 and the
LA distance stated in the problem to calculate a new value for LX.
Does it match the first value you got using resistance?
V1
LX
Fault to gnd
R1
U1
+
0.000
-
V
R3
Faulted Good
LB LA
RA ohms
Short
Page 2 of 2