Download Simulation of DC Reisitve Circuits

EE 3010 - Laboratory
Experiment 2
Experiment 2: Simulation of DC Resistive Circuits
Objectives:
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Simulate DC Resistive circuits using Multisim Software.
Verify experimental and theoretically calculated results for a given resistive network.
Investigate voltmeter loading effects.
Pre Lab:
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Bring a USB memory device to lab. You will need it to save your files.
Read and understand Appendix D in the text.
Do problem 2.22. Determine the current passing through the 12-resistorthe 25- resistor, and
the voltage drop across the 30-resistor. Bring your detailed solution to lab. Enter these values
on Table 1 of the Data Sheet.
Transfer your measured resistor values from Experiment 1 to Table 2 of the Data Sheet
Transfer your measured voltage and current values from Experiment 1 for voltage source and
resistors to Table 3 of the Data Sheet.
Using your measured resistor values from Experiment 1, Figure 2 calculate theoretical voltages
and currents for the circuit described by Experiment 2, Figure 1. Enter these values on Table 3 of
the Data Sheet.
Components Used:
Multisim Software for the PC supplied on one of the CDs with the text.
Part A: Introduction to Multisim
Procedure:
1. Using the computer in the laboratory, start the Multisim software and follow the example
described in the Multisim Tutorial.pdf. Ask your Lab Instructor for help if necessary.
2. Save the completed circuit as a file to your diskette. This circuit can be printed to the network
printer. You may also copy the circuit and paste it in a word document as a circuit schematic and
include with your lab report.
3. Create a circuit for Problem 2.22 of the text and record the current value through the 12 resistor
on Table 1 of the Data Sheet.
4. Click on the current (voltage) icon to display the element currents (node voltages). Record values
on Table 1 of the Data Sheet. (You will need to calculate the difference between two node
voltages to determine the voltage across the 30 Ω resistor.)
Conclusions:
1. Does the simulation provide accurate values when compared with calculated values? Explain.
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EE 3010 - Laboratory
Experiment 2
Part B: Parallel and Series Circuit
Procedure:
1. Figure 1 is the schematic for the final circuit constructed in Experiment 1. As a prelab activity,
you should have transferred measured values for R1, R2, R3, and R4 to Table 2 of the Data Sheet.
You should have also transferred measured and calculated values for voltages and currents to
Table 3 of the Data Sheet.
2. Construct a schematic of the circuit shown in Figure 1 using Capture. Assign the measured values
from experiment 1 to the components of this schematic. Change the values by double clicking on
the component and editing the value cell. Components may be rotated or flipped by right clicking
on a component and using the pop-up menu.
Figure 1
3. Run the bias point simulation and record the values for current through and voltage across each
component in Table 3 of the Data Sheet.
Conclusions:
1. Does the simulation provide accurate values when compared with both measured values and
calculated values? Explain.
Part C: Instrument Loading
Voltmeters have very high resistances that typically exceed 1 MEG If the circuit uses relatively
low resistance components (say, less than 10Kthe resistance of the voltmeter has a negligible
effect on the circuit. However, this is not always the case. When a voltmeter changes the voltages in
the circuit being measured, we say that the meter “loads” the circuit. In Part C we investigate loading
caused by the internal resistance of a voltmeter and its effect on a circuit.
Procedure:
1. Construct the circuits shown below using Multisim. Record the voltages in Table 4 of the data
sheet.
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EE 3010 - Laboratory
Experiment 2
2. Now suppose that we have these circuits actually set up in the lab and we want to measure the
voltages at nodes A and B. Voltmeters have finite resistances. In other words, they draw some
current from the circuit that they are measuring. A model for a typical voltmeter is a 1 MEGΩ
resistance. Add 1 MEG Ω resistors from A to the reference node and from B to the reference
node in each circuit to model voltmeters used to measure the node voltages. Simulate the circuit
and record the node voltages in Table 4.
1
R1
4
2kΩ
V1
15 V
R2
2kΩ
R3
2kΩ
0
1
R1
4
2MΩ
V1
15 V
R2
2MΩ
R3
2MΩ
0
Conclusions:
1. Comment on the effect that the resistance of the voltmeter has on the voltages. When should we
be suspicious that a voltmeter might load a circuit being measured? When is it likely to not be a
problem?
Abbreviations:
F
P
N
U
M
K
MEG
G
T
femtopiconanomicromillikilomegagigatera-
10^-15
10^-12
10^-9
10^-6
10^-3
10^3
10^6
10^9
10^12
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EE 3010 - Laboratory
Experiment 2
Data Sheet
Table 1: Problem 2.18
Calculated
(Prelab)
Table 3: Parallel and Series Circuit
Simulation
V 51 0
I12
I 5 10
I25
V 11 00
V30
I 1 10 0
Table 2: Measured Resistor Values
Nominal Value
(Ohms)
V 2 0 00
I 2 00 0
Measured Value
(From Experiment 1)
V 3 00
I 3 00
R1
R2
R3
R4
Table 4: Instrument Loading
VA
VB
Original Circuits
Circuits with “voltmeters” added
Your Name_____________________________
Partner Name___________________________
Lab Instructor___________________________
Page 4 of 4
Date______________