Download Lab 5 Handout

Network Theorems – Part 1
Lab Experiment No. 5
Intro to EE, Freshman Practicum
I. Introduction
The purpose of this lab is to gain familiarity with several important Electrical Engineering theorems. The experiments
performed in this lab involve the following concepts –
 Superposition theorem
 Learn how a semiconductor device called a zener diode can be used as a reasonable alternative to a voltage
source
The theory and equations associated with these experiments are covered in your class notes. Your job in this session is
to investigate and apply the above theorems on resistive networks to provide a hands-on experience to the theory covered
in the lectures on these topics. For each of the networks given below, use the parts supplied by the GTA, and the DMM
and dc power supply located on the lab bench.
II. Experiment Procedures
Procedures for performing experiments on a collection of resistive networks are attached. These experiments involve the
theory and applications covered in the lecture on superposition, thevenin’s equivalent and Zener diode operation. In
your lab report, provide detailed answers and discussions to the following –
• Discussion.
(a) With respect to resistor tolerance, are the results of the measurements within tolerance to calculated values
using specified component values?
(b) Explain reasons for any discrepancies between calculated and measured results.
(c) How useful are these theorems and operations? Can you think of any specific applications?
III. Superposition
Part A. Network N4.
1. Build network N4 shown in Figure 1 on multisim.
2. Measure the values of each resistor with the DMM and record in Table 1(a) where indicated.
3. Perform the following operations.
a. With EG1 turned on and operating, measure its value and record in Table 1(a) then turn off voltage source
EG2 by removing it from the connection and replacing it with a short circuit,
i. calculate voltage VAB using the specified component values and record in Table 1(b),
ii. calculate voltage VAB using the measured component values and record in Table 1(b),
iii. measure with the DMM voltage VAB from the breadboard and record in Table 1(b), and
iv. calculate the difference in percent (%) between VAB measured and VAB calculated with specified
component values as the basis, and record in Table 1(b).
b. With EG2 turned on and operating, measure its value and record in Table 1(a) then turn off voltage source
EG1 by removing it from the connection and replacing it with a short circuit,
i. calculate voltage VAB using the specified component values and record in Table 1(b),
ii. calculate voltage VAB using the measured component values and record in Table 1(b),
iii. measure with the DMM voltage VAB from the breadboard and record in Table 1(b), and
iv. calculate the difference in percent (%) between VAB measured and VAB calculated with specified
component values as the basis, and record in Table 1(b).
c. Apply the superposition theorem to
i. calculate the total voltage for VAB by adding the values calculated from specified component values,
record in Table 1(b), and
ii. calculate the total voltage for VAB by adding the values calculated from measured component values,
record in Table 1(b).
d. With EG1 and EG2 turned on and operating,
i. measure the total voltage VAB directly from N4, and
ii. calculate the difference in percent (%) between the total VAB measured from N4 (3di) and the total
VAB calculated with specified component values (3ci) as the basis, and record in Table 1(b).
4. Provide comments on the accuracy of superposition for providing precise voltage measurements and on the
ease of making these measurements.
Lab Report : Multisim Simulation of Circuits
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R1
R2
A
30K
EG1
14V
15K
R3
VAB
7.5K
EG2
14V
N4
B
Figure 1
Network N4
Table 1(a)
N4 component values
Component
Specified value
EG1
14V
EG2
14V
R1
30KΩ
R2
15KΩ
Measured value
Table 1(b)
N4 voltages
Voltage
Calculated from
specified R values
(V)
Calculated from
measured R values
(V)
Measured from N4
(V)
Difference
(%)
VAB (EG2 = 0)
VAB (EG1 = 0)
VAB (total)
Lab Report : Multisim Simulation of Circuits
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38
Part B. Network N5.
1. Build network N5 shown in Figure 2 on multisim
2. Perform the operations similar to those performed in Part A.
a. With EG1 turned on and operating, turn off voltage source EG2 by removing it from the connection and
replacing it with a short circuit, measure voltages VAB and VCD, and record in the first column of Table 2.
b. With EG2 turned on and operating, turn off voltage source EG1 by removing it from the connection and
replacing it with a short circuit, measure voltages VAB and VCD, and record in the second column of Table
2.
c. Apply the superposition theorem to calculate total measured values for VAB and VCD, and record in the
third column of Table 2.
d. With EG1 and EG2 turned on and operating, measure VAB and VCD directly from N5, and record in the fourth
column of Table 2.
e. Calculate the difference in percent (%) between VAB and VCD measured directly from N5 (fourth column)
and VAB and VCD calculated from superposition (third column) with the measured values as the basis.
Record in the last column of Table 2.
3. Provide comments on the accuracy of superposition for providing precise voltage measurements and on the
ease of making these measurements.
R1
1K
EG1
R2
A
N5
R3
D
8.2K
15V
5.1K
R5
6.8K
R4
4.7K
EG2
R6
C
3.9K
B
12V
R7
2.7K
Figure 2
Network N5
Table 2
N5 voltages
Voltage
Measured with
EG2 = 0
(V)
Measured with
EG1 = 0
(V)
Total from
superposition
(V)
Total
measurement
(V)
Difference
(%)
VAB
VCD
Lab Report : Multisim Simulation of Circuits
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IV. Zener Diode
1.
2.
3.
4.
5.
6.
Build the circuit shown in Figure 4 in multisim. Include a voltmeter to measure the voltage across the 4.3 V
source with the reference shown and an ammeter to measure the current flowing right to left through the 4.3 V
source. (Note: for easy wiring, you can right-click on the meters in your circuit, and flip them horizontally.) on
multisim.
Change the resistor tolerance to 0 %.
Run the simulation. Enter the voltage and current into the appropriate place of Table 4
Replace the 4.3 V source with the zener diode (model number 1N749A) as shown in Figure 5. Repeat Step 3
with supply voltages (Vsupply) of between ± 20 V in steps of 4 V (i.e., -20 V, -16 V, -12 V, etc.) and place
your results in Table 5 in the lab report and in your lab note section..
Plot the I-V characteristics of the diode using the data from Table 5 of the Lab Report. You should either do a
**CLEAR** plot by hand or use a program like EXCEL and paste the results in the space provided
Turn in your completed lab report to your TA.
Figure 4: Third Simulation Circuit
Figure 5: Third Circuit Using a Zener Diode
Table 4: Simulated values for Figure 4 of the lab
4.3 V Source Voltage
4.3 V Source Current
Table 5: Voltage and Current Values for the Diode in Figure 5 of the lab.
Lab Report : Multisim Simulation of Circuits
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Supply Voltage
Value (V)
Diode
Voltage (V)
Diode
Current (mA)
Plot the I-V characteristics of the diode using the data from Table 4. You should either do a **CLEAR** plot by
hand or use a program like EXCEL and paste the results in the space provided below.
Can you use a Zener Diode to replace a voltage source in a circuit? If so, how well does it match the operation of an
ideal voltage source?
Lab Report : Multisim Simulation of Circuits
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