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Unformatted text preview: LABORATORY MANUAL
DEPARTMENT OF
ELECTRICAL & COMPUTER ENGINEERING UNIVERSITY OF CENTRAL FLORIDA EEL 3123
ELECTRICAL NETWORKS PREPARED BY DR. TAKIS KASPARIS REVISED FALL 2005 PREFACE
This laboratory book for Electrical Networks was first introduced in 1990 and since then
it has been revised several times in order to be up to date with curriculum changes,
laboratory equipment upgrading, and the latest circuit simulation software.
Every effort has been made to correct all the known errors, but nobody is perfect. If you
find any errors or anything else that you think is an error, please contact Dr. Kasparis at:
[email protected]
The contribution of Mr. Enrique Tenicela who diligently worked to redraw all the figures
in this manual needs to be acknowledged. Dr. Takis Kasparis
Fall 2005 2 TABLE OF CONTENTS
SAFETY RULES AND OPERATING PROCEDURES
LABORATORY SAFETY INFORMATION
INTRODUCTION
GUIDELINES FOR LABORATORY NOTEBOOK
TROUBLESHOOTING HINTS EXPERIMENT # 1 DC MEASUREMENTS EXPERIMENT # 2 AC MEASUREMENTS EXPERIMENT # 3 NETWORK ANALYSIS METHODS EXPERIMENT # 4 FIRST ORDER CIRCUITS EXPERIMENT # 5 SECOND ORDER CIRCUITS EXPERIMENT # 6 SINUSOIDAL STEADY STATE EXPERIMENT # 7 SERIES AND PARALLEL RESONANCE EXPERIMENT # 8 TRANSFER FUNCTIONS EXPERIMENT # 9 FREQUENCY RESPONSE EXPERIMENT ENALUATION FORM APPENDIX RESISTOR COLOR CODE TUTORIAL
LIST OF AVAILABLE RESISTORS AND CAPACITORS 3 Safety Rules and Operating Procedures 1. Note the location of the Emergency Disconnect (red button near the door) to shut
off power in an emergency. Note the location of the nearest telephone (map on
bulletin board).
2. Students are allowed in the laboratory only when the instructor is present.
3. Open drinks and food are not allowed near the lab benches.
4. Report any broken equipment or defective parts to the lab instructor. Do not
open, remove the cover, or attempt to repair any equipment.
5. When the lab exercise is over, all instruments, except computers, must be turned
off. Return substitution boxes to the designated location. Your lab grade will be
affected if your laboratory station is not tidy when you leave.
6. University property must not be taken from the laboratory.
7. Do not move instruments from one lab station to another lab station.
8. Do not tamper with or remove security straps, locks, or other security devices. Do
not disable or attempt to defeat the security camera.
9. ANYONE VIOLATING ANY RULES OR REGULATIONS MAY BE DENIED
ACCESS TO THESE FACILITIES. I have read and understand these rules and procedures. I agree to abide by these rules
and procedures at all times while using these facilities. I understand that failure to follow
these rules and procedures will result in my immediate dismissal from the laboratory
and additional disciplinary action may be taken. ___________________________________
Signature
Date _______________
Lab # 4 Laboratory Safety Information
Introduction
The danger of injury or death from electrical shock, fire, or explosion is present while conducting
experiments in this laboratory. To work safely, it is important that you understand the prudent
practices necessary to minimize the risks and what to do if there is an accident.
Electrical Shock
Avoid contact with conductors in energized electrical circuits. Electrocution has been reported at dc
voltages as low as 42 volts. Just 100ma of current passing through the chest is usually fatal. Muscle
contractions can prevent the person from moving away while being electrocuted.
Do not touch someone who is being shocked while still in contact with the electrical conductor or you
may also be electrocuted. Instead, press the Emergency Disconnect (red button located near the
door to the laboratory). This shuts off all power, except the lights.
Make sure your hands are dry. The resistance of dry, unbroken skin is relatively high and thus
reduces the risk of shock. Skin that is broken, wet or damp with sweat has a low resistance.
When working with an energized circuit, work with only your right hand, keeping your left hand away
from all conductive material. This reduces the likelihood of an accident that results in current passing
through your heart.
Be cautious of rings, watches, and necklaces. Skin beneath a ring or watch is damp, lowering the skin
resistance. Shoes covering the feet are much safer than sandals.
If the victim isn't breathing, find someone certified in CPR. Be quick! Some of the staff in the
Department Office are certified in CPR. If the victim is unconscious or needs an ambulance, contact
the Department Office for help or call 911. If able, the victim should go to the Student Health Services
for examination and treatment.
Fire
Transistors and other components can become extremely hot and cause severe burns if touched. If
resistors or other components on your protoboard catch fire, turn off the power supply and notify the
instructor. If electronic instruments catch fire, press the Emergency Disconnect (red button). These
small electrical fires extinguish quickly after the power is shut off. Avoid using fire extinguishers on
electronic instruments.
Explosion
When using electrolytic capacitors, be careful to observe proper polarity and do not exceed the
voltage rating. Electrolytic capacitors can explode and cause injury. A first aid kit is located on the
wall near the door. Proceed to Student Health Services, if needed. 5 INTRODUCTION
This first laboratory in Electrical Engineering has the objectives to familiarize the student
with the operation of basic laboratory instrumentation such as oscilloscope, function generator,
multimeter, frequency counter, and also with personal computers and circuit simulators such as
Pspice and Workbench. Another goal is to reenforce theoretical knowledge with practice and
viceversa, and also to learn correct laboratory procedures and techniques.
This is
accomplished by building, testing, and taking measurements on simple circuits.
In the execution of the experiment, highest benefit is gained if someone can distinguish
between performing the experiment by following stepbystep instructions, and actually
understanding the reasons and the methodology behind the various parts. To understand the
experiments you must understand the theory of the circuits under test, and the instruments used
to test them. To convey the experimental results, you must learn to write a correct laboratory
report.
The experiments are organized as follows: for each experiment a brief
background is
given. This background does not completely cover the theory behind each experiment, but
provides highlights. References at the end of each experiment are provided for more details.
The preparation part provides all the theoretical calculations that a student must prepare before
coming to the lab. The key to a successful and beneficial experiment is to understand the
theory, be prepared, and know what you
expect to get in the lab. It is essential that all
students come to the lab prepared. Most experiments have a computer simulation part. Circuit
simulators provide the capability to do an experiment without going into any lab, and without
building the actual circuit. The simulation part of each experiment duplicates the preparation
part, and provides the student with a confirmation that the theoretical calculations are correct.
However, no simulator can substitute the actual experiment. In the experimental part the student
performs the actual experiments, where he/she obtains "hands on" experience on how to
correctly connect circuits, and use the various laboratory equipment. The design part gives the
student the opportunity to create a circuit, or freely select component values to meet some
specifications. No experiment is complete without a report. In the report the student presents
all the work involved in an experiment, and also all the benefits that were gained.
Most experiments are designed to be one week experiments, if properly prepared.
However, usually expectations do not meet reality, and therefore time can be allowed, if
needed. 6 GUIDELINES FOR LABORATORY NOTEBOOK
The laboratory notebook is a record of all work pertaining to the experiment. This record should be
sufficiently complete so that you or anyone else of similar technical background can duplicate the
experiment and data by simply following your laboratory notebook. Record everything directly into the
notebook during the experiment. Do not use scratch paper for recording data. Do not trust your memory
to fill in the details at a later time.
Organization in your notebook is important. Descriptive headings should be used to separate and
identify the various parts of the experiment. Record data in chronological order. A neat, organized and
complete record of an experiment is just as important as the experimental work.
1. Heading: The experiment identification (number) should be at the top of each page. Your name
and date should be at the top of the first page of each day's experimental work.
2. Object: A brief but complete statement of what you intend to find out or verify in the experiment
should be at the beginning of each experiment
3. Diagram: A circuit diagram should be drawn and labeled so that the actual experiment circuitry
could be easily duplicated at any time in the future. Be especially careful to record all circuit
changes made during the experiment.
4. Equipment List: List those items of equipment which have a direct effect on the accuracy of the
data. It may be necessary later to locate specific items of equipment for rechecks if discrepancies
develop in the results.
5. Procedure: In general, lengthy explanations of procedures are unnecessary. Be brief. Short
commentaries along side the corresponding data may be used. Keep in mind the fact that the
experiment must be reproducible from the information given in your notebook.
6. Data: Think carefully about what data is required and prepare suitable
instrument readings directly. Do not use calculated results in place of
calculated results may be recorded in the same table with the direct data.
clearly identified and each data column labeled and headed by the proper data tables. Record
direct data; however,
Data tables should be
units of measure. 7. Calculations: Not always necessary but equations and sample calculations are often given to
illustrate the treatment of the experimental data in obtaining the results.
8. Graphs: Graphs are used to present large amounts of data in a concise visual form. Data to be
presented in graphical form should be plotted in the laboratory so that any questionable data
points can be checked while the experiment is still set up. The grid lines in the notebook can be
used for most graphs. If special graph paper is required, affix the graph permanently into the
notebook. Give all graphs a short descriptive title. Label and scale the axes. Use units of
measure. Label each curve if more than one on a graph.
9. Results: The results should be presented in a form which makes the interpretation easy. Large
amounts of numerical results are generally presented in graphical form. Tables are generally
used for small amounts of results. Theoretical and experimental results should be on the same
graph or arrange in the same table in a way for easy correlation of these results.
10. Conclusion: This is your interpretation of the results of the experiment as an engineer. Be brief
and specific. Give reasons for important discrepancies. 7 TROUBLESHOOTING HINTS
1. Be sure that the power is turned on.
2. Be sure the ground connections are common.
3. Be sure the circuit you built is identical to that in the diagram. (Do a nodebynode check.)
4. Be sure that the supply voltages are correct.
5. Be sure that the equipment is set up correctly and you are measuring the correct
parameter.
6. If steps 1 through 5 are correct, then you probably have used a component with
the wrong value or one that doesn't work. It is also possible that the equipment
does not work (although this is not probable) or the protoboard you are using
may have some unwanted paths between nodes. To find your problem you must
trace through the voltages in your circuit node by node and compare the signal
you have to the signal you
expect to have. Then if they are different use your
engineering judgment to decide what is causing the different or ask your lab
assistant. 8 EXPERIMENT # 1
DC MEASUREMENTS
DC POWER SUPPLY, DIGITAL MULTIMETER
OBJECTIVE: To introduce the measurements of DC voltage and current, and resistance.
EQUIPMENT:
Digital multimeter (DMM)
Power supply
Resistors
BACKGROUND:
To measure voltage, a voltmeter is connected between the two points where the voltage is to be
measured (see fig.1). Since this is a parallel connection, an ideal voltmeter should have infinite
internal resistance, so that the value of the unknown voltage will not be affected by the voltmeter
connection. To measure the current through a branch, the branch has to be broken and an ammeter
is inserted in the branch (see fig.2). Since this is a series connection, a good ammeter should have
very small internal resistance .Ohmmeters convert resistance measurement into voltage or current
measurement. An ohmmeter has an internal voltage source, and when an unknown resistor is
placed across its terminals, a closedloop is formed (see fig.3).
PREPARATION:
In the circuits of Figures 4 and 5, 6 and 7 select any available values for all resistors in the range
above 1 KΩ and below 56 KΩ. You choose the values. Resistors with the same name have the
same value, but resistors with different names should not have the same value.
a)
b)
c)
d)
e) In the circuit of Fig.4 calculate V1, V2, and I. Verify the voltage divider rule and KVL (by
verifying that V1 + V2 = 9V).
In the circuit of Fig.5 calculate I1, I2, I, and Vx. Verify the current divider rule and KCL (by
verifying that I1 + I2 = I).
In the circuit of Fig.6 calculate the equivalent resistance between points AB and also between
points CD (How?). Assume that all resistors have the same available value of your choice.
In the circuit of Fig.7 calculate voltage Vx.
The DVM has an internal resistance of 10 MΩ typically. Assume that in the circuit of fig.8, a
DVM is used to measure the voltage Vx. Calculate the reading if:
1) R = Any value between 1 KΩ and 10 KΩ
2) R = Any value above 2 MΩ EXPERIMENT:
The purpose of the experiment is to experimentally verify the theoretical results calculated in the
preparation. Use the same resistor values as in the preparation.
a) Use the DMM as an ohmmeter and measure the values of all resistors to be used. Compare
the actual with the nominal value. The nominal value can be determined from the color code
on the resistor.
Note: When taking a resistance measurement do not touch both resistor terminals
with your fingers. The resistance of your body can alter the reading.
b) Connect the circuit of Fig.4 and measure V1, V2, and I. Verify KVL, and Ohm's law by
computing R1 = V1/I and R2 = V2/I. Verify also the voltage divider rule.
c) Connect the circuit of Fig.5 and measure I1, I2, I, and Vx. Verify the current divider rule, and
KCL.
d) Connect the circuit of Fig.6 and measure the resistance between points AB, and CD.
e) Connect the circuit of Fig.7 and measure Vx.
f) Connect the circuit of Fig.8 and measure Vx for both cases as in preparation part (e). REPORT:
In your report compare all the theoretical and experimental values and make comments on any
discrepancies. Write all conclusions. 9 FIGURES 10 EXPERIMENT # 2
AC MEASUREMENTS
OSCILLOSCOPE, FUNCTION GENERATOR
FREQUENCY COUNTER
OBJECTIVES:
To introduce the oscilloscope, the function generator, and the frequency counter in measuring AC
parameters of signal.
EQUIPMENT:
Oscilloscope
Function generator
Frequency counter
Resistor substitution box
Capacitor substitution box
BACKGROUND:
An AC (time varying) signal requires several parameters to be completely described. The problem of
measuring AC signals is how to determine these parameters. The frequency counter can be used to
measure the frequency or the period of a periodic signal of any waveform. AC multimeters produce
a DC value proportional to an AC parameter of the signal to be measured. Most multimeters are
calibrated to display the RMS value of sinusoid waveforms only. The oscilloscope can be used for
any AC measurement. The waveshape can be visually examined on the screen of the instrument. It
should be emphasized that only periodic waveforms can generate a stationary pattern on the screen
of an analog oscilloscope. Modern digital scopes can capture, store, and display sections of arbitrary
waveforms. The function generator is a versatile AC signal source. It can provide several waveshapes, and the amplitude and the frequency can be adjusted
PREPARATION:
a) Familiarize your selves with the instruments in your station on the bench.
b) Study the instrument's user manuals if available.
c) Calculate the period of a waveform of frequencies 100 Hz, 1kHz, 100 kHz.
EXPERIMENT:
A) Oscilloscope general
1) Connect the output of the function generator to ch.1 of the scope, and also to the input of the
frequency counter. Set the trigger to ch.1, coupling DC.
2) Select sinusoidal waveform on the generator. Vary the frequency and the amplitude on the
generator and observe the results on the scope.
3) Vary the gain and the timebase of the scope and observe the results.
4) Set the amplitude on the generator for 5V peak. Adjust the "level" control on the scope until the
waveform just becomes stationary.
5) Decrease the amplitude from the generator, and observe that triggering is lost (waveform starts
running). Why?
6) Readjust the "level" control for stationary waveform. 7) Select any waveform and frequency and adjust the "DC offset" control on the generator.
Observe the result on the scope. 11 8) Set the coupling on the scope to AC and repeat step 8. What do you observe? Make comments.
B) Voltage measurements
1) Set the generator to a sine wave of frequency 100 Hz and 10V amplitude.
2) Connect the DMM to the output of the generator and set it to measure AC voltage. Verify that
the DMM reads the correct RMS value of the sinusoid (equal to 7.07V).
C) Frequency measurements
1) Set the generator to sinusoid of frequency 100 Hz and measure the period of the waveform on
the scope. Repeat for 1 kHz and 100 kHz, and confirm the results found in part (e) of the
preparation.
Note: The period can be measured on the oscilloscope as the time between two successive
peaks or two successive zero crossings.
2) Repeat step (1) for triangular and squarewave.
REPORT:
In your report describe the work you have done in the lab, and present the measurements you have
taken. Compare theoretical and experimental results and make comments. Write all conclusions. 12 EXPERIMENT # 3
MESH AND NODE EQUATIONS
THEVENIN AND NORTON EQUIVALENTS
SUPERPOSITION THEOREM
OBJECTIVES:
To use node and mesh equations to analyze a resistive network. Verify Thevenin and Norton
theorems, and the principle of superposition, and the maximum power transfer theorem.
EQUIPMENT:
Power supply
Function generator
Digital voltmeter
Oscilloscope
Resistors
Resistance box
BACKGROUND:
Analyzing a network means to calculate the voltage and current of each element. Two systematic
methods for analyzing networks are node and mesh equations. Thevenin’s theorem is a powerful
theorem in modeling any linear circuit. The dual is Norton's theorem. Refer to your textbook for
more details.
PREPARATION:
Consider the circuit in figure 1. For all resistors choose available values in the range 1K to 50K. You can use the
same value twice, but do not make all resistors equal.
1) Assume that points AB are shorted. Assign mesh currents, write and solve the mesh equations.
From the mesh currents calculate the voltage across each resistor, and the current through AB.
2) Assume that points AB are not shorted. Write and solve the node equations. From the node
voltages calculate the voltage across each resistor, and the voltage between points AB.
3) Use data calculated in parts (a) and (b) to find the Thevenin and Norton equivalents
4) Assume that a resistor box is connected between points AB. Calculate the current through this
resistor for values 1 kΩ, and 2.2 kΩ and 4.7 kΩ. (Hint: use the Thevenin equivalent).
5) Set E2 and E3 to zero and calculate the voltage between points AB. Repeat this step two more
times by setting E1, E2 and E1, E3 to zero. Check if the sum of the three voltages checks with
the one found in part (2).
SIMULATION:
Use your circuit simulator to verify the theoretical results you have found in parts (1) (2) (4) and (6).
EXPERIMENT:
The purpose of the experiment is to experimentally verify the results you have calculated in the
preparation, and you have also simulated. Since all resistors have tolerances, use the ohmmeter to
measure the actual value of all the resistors used.
Wire the circuit of Figure 1 using the values you have chosen in the preparation.
Note: To be able to independently adjust the positive and the negative outputs of the power supply,
you must set the "Tracking ratio" to "variable" position.
Warning: In the subsequent sections, the phrase "set a voltage source to zero,” means disconnect
the terminal from the power supply and connect it to ground. Under no circumstances
short any power supply output to ground. 13 A) Mesh equations:
1) Short points AB and measure the voltage across each resistor.
2) Use the ammeter to measure the current through AB.
3) Compare the results with the ones found in part (1) of the preparation.
B) Node equations:
1) Open points AB and measure the voltage across each resistor.
2) Measure the voltage between points AB.
3) Compare with part (2) of preparation.
C) Thevenin and Norton equivalents
1) Set all the sources to zero and use the DMM to measure the resistance between points AB.
2) Compare the result with part (3) of preparation.
3) Connect back all the voltage sources and connect the resistance box with the ammeter in
series between points AB. Select values as in part (4) of the preparation and measure the
current. Compare with the expected results.
D) Superposition theorem: Remove the resistance box from points AB
1) Do the steps described in part (5) of the preparation. Check if the sum of the three individual
voltages agrees with the one found in part B.2 of the experiment.
2) Set E1 to zero and measure the voltage at points A, B due to E2 and E3. Next, set E2 and E3
to zero and measure the same voltage due to E1. Check if the sum of the two agrees with the
voltage found in part B.2 of the experiment.
REPORT:
In your report present the measurements you have taken in the lab and compare them with the
theoretical and simulated. Write all your comments and conclusions. 14 EXPERIMENT # 4
FIRSTORDER CIRCUITS
OBJECTIVES: To study the step response of first order circuits
EQUIPMENT:
Oscilloscope
Function Generator
100 mH inductor
Resistor substitution box
Capacitor substitution box
BACKGROUND:
Consider the series RC circuit shown in fig.1a. The capacitor voltage is given by: Vc (t ) = E (1 − e − t / RC ) , t ≥0 This voltage is illustrated in fig.1b. The voltage across the resistor can be found to be: VR (t ) = Ee − t
RC , t≥0 and it is plotted in Figure1.c. Similar analysis can be done for the RL circuits of fig.2.
PREPARATION:
a) Consider the circuits in Figure 2. For each circuit derive analytical expressions for Vo(t) when
Vi(t)=Eu(t) (step of amplitude E). Assume zero initial conditions. Plot Vi(t) for each circuit.
b) Repeat part (a) assuming that Vi(t) is a symmetric squarewave of amplitude ±E, and period Ts=10
RC. (Hint: use superposition).
SIMULATION:
For the circuits of figures 1 and 2 assume R = 1K, C = 0.1 μF, L = 100 mH, R1 = 2.2 K, R2 = 2.2 K.
The input is a symmetric squarewave of amplitude ±5V and frequency of 1 kHz. Run simulations
to plot Vo(t).
EXPERIMENT:
The purpose of the experiment is to experimentally verify the results you have derived in the
preparation, and also have simulated using. The steps below apply to all circuits in figures 1, and 2.
Use the same component values as in simulations.
a) Wire one circuit at a time. Connect vi(t) to the function generator, set at 1 kHz frequency, and
squarewave output of amplitude ±5V.
b) Connect ch.1 of the oscilloscope to vi and ch.2 to vo. Set the trigger to ch.1
c) Observe and sketch the output voltage and compare it to the expected one.
d) Take measurements on the oscilloscope to determine the time constant of the circuit, and compare
the result with the actual one. REPORT:
In your report present and compare the results that you have obtained theoretically, experimentally,
and via computer simulation, and make comments. Write all conclusions. 15 FIGURES 16 EXPERIMENT # 5
SECOND ORDER CIRCUITS
OBJECTIVES: To study the step response of RLC circuits.
EQUIPMENT:
Oscilloscope
Function Generator
100 mH inductor
Capacitor Box
Resistance Box
BACKGROUND:
Secondorder circuits have a stepresponse depending on the nature of the roots of the characteristic
equation.
PREPARATION:
A) Consider figure 1. Assume zero initial conditions.
1) For L = 100 mH and C = 0.01 μF, calculate the ranges of values of R for overdamped,
critically damped, and under damped response.
2) Assume the response to be the voltage across the capacitor. Plot the response due to a step
input for:
a) R = 22 K ; b) R = 6.8 K ; c) R = 2.2 K
3) Let R = 470 Ohm. Calculate α, ωn, and ωd. Plot the voltage across the capacitor due to a
squarewave input of frequency of 400 Hz, and amplitudes of ±4V.
B) Consider figure 2:
1) Find the characteristic equation and the poles.
2) Repeat part (A.1) for the same values of L, C.
3) Repeat part (A.2) for:
a) R = 680 Ohm; b) R = 1.5 K; c) R = 4.7 K;
4) Repeat part (A.3) for R = 22 K
SIMULATION:
Simulate parts A.2, A.3, B.3 and B.4 of the preparation.
EXPERIMENT:
a) Connect the circuit of fig.1. In place of the resistor and the capacitor use the substitution boxes.
b) Connect the input to the function generator. Set to a squarewave of 400 Hz and amplitudes of
±4V.
c) Connect ch.1 of the oscilloscope to the generator output, and ch.2 at the capacitor voltage. Set the
trigger to ch.1.
d) Observe and sketch the capacitor voltage for R = 22 K, R = 6.8K, and R = 2.2 K. For each case
indicate whether the response is over damped or under damped.
e) Let R = 470 Ohm. Sketch the output voltage and using the oscilloscope measure ωd.
f) Repeat part (d) for the circuit of fig.2 and resistor values R = 680 Ohm, R= 1.5 K, and R = 4.7 K.
g) Repeat part (e) for fig.2 with R = 22 K
REPORT:
In your report, present and compare theoretical, computer simulated, and experimental results, and
make comments. Write all conclusions. 17 FIGURES 18 EXPERIMENT # 6
SINUSOIDAL STEADYSTATE
OBJECTIVES: To compute the power factor of a passive circuit and verify the
Conservation of energy in sinusoidal steady state.
EQUIPMENT:
Oscilloscope
Power Supply
Function Generator Capacitors
Resistors BACKGROUND:
Sinusoidal statestate is very important in practice since sinusoidal waveforms are very common.
Power calculations are also very important since the main goal of power systems is the transfer of
power. Consider the circuit of Fig. 1. The average power delivered by the source is: 1
Pav = Vm I m cos(θ )
2
where Vm, Im are the peak values of the voltage and the current. The average power is proportional
to cos (θ), the power factor. Notice that θ is actually the phase difference between the voltage and
the current.
PREPARATION:
Consider the circuit of Fig. 2 with component values as shown (or the closest available). Assume
Vm= 8V and a frequency of 3 KHz.
a) Compute the equivalent complex impedance seen by the source.
b) Compute the power factor.
c) Compute the voltage and current in each element in the circuit.
d) Compute the average power dissipation in each element in the circuit.
e) Compute the average power delivered by the source and verify the
conservation of energy.
f) Show that if the voltage labeled V X = V xm e jφ is known (measured), then the power factor can be computed from PF = cos (θ) , where: ⎧
⎫
⎪
⎪ sin(φ ) ⎪
⎪
θ = tan −1 ⎨
⎬
⎪ Vm − cos(φ ) ⎪
⎪ V xm
⎪
⎭
⎩
SIMULATION:
By using simulations verify your preparation results.
EXPERIMENT:
1) Wire the circuit on Fig. 2. Since the oscilloscope has only two channels, measuring the power
factor is tricky, however, it can be done by using the results in part (f) of the preparation.
2) Use sinusoidal input from the generator with amplitude and frequency as described in the
preparation.
3) Display the input voltage and voltage Vx on the scope. Measure their peak values and their
phase difference (see experiment 2). Compute the power factor using equation (2) above. 19 4) Measure the peak voltage across each element and compute the power dissipation.
5) Verify the conservation of energy.
NOTE: Measure the exact value of each resistor. Assume ideal capacitors and inductors.
DESIGN: a)
b)
c)
d)
e) Investigate experimentally whether there are frequencies between 1 KHz and 20 KHz where the
power factor becomes unity.
If the answer to both (a) and (b) is "yes" check the agreement between the results.
Compute the power delivered by the source under these conditions, and verify the conservation
of energy.
Give a physical explanation as to what happens at these particular frequencies.
Use simulations to verify your results. REPORT:
In your report present experimental results and compare them with the theoretically expected results.
Discuss any discrepancies, make comments and write conclusions. 20 21 EXPERIMENT # 7
SERIES AND PARALLEL RESONANCE
OBJECTIVE: To study the series and parallel LC circuits.
EQUIPMENT:
Oscilloscope
Function Generator
Frequency counter
100 mH inductor
Capacitance substitution box
Resistor substitution box
BACKGROUND:
Consider the series RLC circuit of fig.1. Frequency ω0 = 1 is called the resonance LC frequency. Similar frequency exists for a parallel RLC circuit.
PREPARATION:
1) Consider the circuits in fig.2 with sinusoidal input and at steadystate. For each circuit:
a) Derive the transfer function and plot the frequency response of the magnitude.
b) Calculate the resonance frequency, the halfpower frequencies, and the bandwidth.
2) In the circuit of fig.3 assume L = 100 mH, C = 0.1 μF, vi =Vmsinωt. Calculate the peak value of
a) R = 1 KΩ (or close value)
b) R = 330Ω (or close value)
vc(t) if:
SIMULATION:
a) Assume R = 1K, L 100mH, C = 0.1μF and vi(t) = 5sinωt.
t.
Use simulation to verify the theoretical results of part (1) of the preparation.
b) Use simulation to verify the results of part (2) of the preparation.
EXPERIMENT:
The purpose of this experiment is to experimentally verify the theoretical and simulated results and
notice any discrepancies.
Connect each of the circuit in figures 1,2, and 3, with L =100mH, C = 0.1 μF, R = 1 K, and
vi(t) = 5sinωt. Use the frequency counter to measure frequencies and the oscilloscope to
observe waveforms.
b) Vary the frequency and record the frequency response of each circuit (magnitude only).
Measure the resonance frequency, the halfpower frequencies, the bandwidth, and the quality
factor. Compare with the expected values. Check if the resonance frequency is the geometric
mean of the halfpower frequencies.
c) For the circuit of fig.3 measure the peak value of the capacitor voltage at the resonance
frequency, when R = 1 K and when R = 330 Ω. Measure also the phaseshift from the input
voltage. Compare with the theoretical values. a) REPORT:
In your report provide simulated and experimental responses, and compare theoretical, simulated,
and experimental results, Make comments on any discrepancies and write conclusions. 22 FIGURES 23 EXPERIMENT # 8
TRANSFER FUNCTIONS
OBJECTIVE: To study the transfer functions of various RC network.
EQUIPMENT:
Oscilloscope
Function generator
Frequency counter
Resistors
Capacitors
BACKGROUND:
A twoport linear network can be in general described by a transfer function H ( jω ) = Vo (ω ) / Vi (ω )
Given a sinusoidal input voltage Vi(t) = Vmsin(ωot), the output voltage will be : Vo (t ) = H ( jω o ) ⋅ Vm sin(ω o t + θ (ω o ))
where H(jωo) and θ(ωo) are the magnitude and the phase of the transfer function at frequency ωo.
PREPARATION:
For all circuits select component values so that RC is any value from 0.1 mS to 0.01mS.
A) Refer to the circuits in fig.1.a and 1.b.
1) For each circuit, find the sinusoidal steadystate transfer function.
2) Assume that the input is a sinusoid. Find the frequency wherethe output voltage will be 45o out of phase,
than the input voltage. Find the amplitude of the output voltage at this frequency.
3) Find the frequency where the amplitude of the output voltage is 1/4 of the amplitude of the input voltage.
B) Refer to the circuit in figures 2 and 3.
1) Verify that the transfer function is the one given in each figure.
2) Assume sinusoidal input. Find the frequencies where the phase difference of input and output voltages is
either +90 or 90 degrees. Find the amplitude of the output voltage at these frequencies.
3) Repeat part (2) for 0o or 180o phase shift.
SIMULATION:
Run simulations to verify the theoretical results found in the preparation. The amplitude of the
sinusoidal input is 10V.
EXPERIMENT:
a) Connect the circuits of figures 1.a and 1.b. Use component values as in the preparation and
simulations.
b) Experimentally verify the results you have calculated in parts A.2 and A.3 of the preparation.
What is the maximum phase shift that can be achieved with these circuits? Are there any
limitations in achieving this phaseshift?
c) Connect the circuits of figures 2 and 3, with component values as in the preparation.
d) Experimentally verify the results you have calculated in parts B.2 and B.3 of the preparation. REPORT:
In your report present your work, and compare the results you have obtained theoretically, via
simulation, and experimentally. Write any comments and conclusions. 24 FIGURES 25 EXPERIMENT # 9
FREQUENCY RESPONSE
OBJECTIVES: To study the frequency response of various RC network.
EQUIPMENT:
Oscilloscope
Frequency counter
Function Generator
Resistors
Capacitors
BACKGROUND:
Refer also to the previous experiment. Frequency response refers to the variation of H(jω) and
phase {H(jω)}, when ω varies. This variation can be plotted either in a linear or a logarithmic scale.
PREPARATION:
a) Derive the transfer function of the circuits in Figures 1 and 2.
b) Find the 3db frequencies as function of the component values.
c) Roughly sketch the magnitude and the phase plots on a linear scale, and indicate whether these
circuits are lowpass or highpass filters. For figures 1 and 2 find the phaseshift at the 3 db
frequency.
SIMULATION:
For all circuits select reasonable and available component values. For the circuit of Figure 3.A select
C1>> C2. Do not use electrolytic capacitors. Use circuit simulation to obtain the frequency response
of each circuit in the range 100 Hz to 100 kHz. Verify any theoretical results you have derived in the
preparation. EXPERIMENT:
The input is connected to the function generator, adjusted for a sinusoid waveform of amplitude
10V. Use the frequency counter to measure frequencies.
a) Connect the circuits of Figures 1 and 2 and vary the input frequency from 100 Hz to 10 kHz,
while observing the output voltage. Take enough measurements to enable you to plot the
magnitude and the phase of the transfer function.
b) Find the 3db frequency, and the phase shift at this frequency. Compare to the theoretical values.
c) Connect the circuits of fig.3 and take measurements to plot the magnitude only of the transfer
functions in a frequency range of 100 Hz to 100 kHz. Measure the 3db frequencies and the
bandwidth. Make comments about the shape of the curves.
REPORT:
Print the frequency responses obtained by, and on the same graphs superimpose the experimentally
obtained plots. Provide these plots in your report and make comments about any discrepancies, and
state all conclusions. 26 FIGURES 27 EXPERIMENT EVALUATION FORM
COURSE : EEL 3123 SEMESTER: COURSE INSTRUCTOR: LAB INSTRUCTOR: EXPERIMENT: Please write comments on the following issues PART A (experiment):
1) Was the experiment successful?
2) Did the experimental results match the theory?
3) Was the material covered in the lecture?
4) Was the experiment instructive?
5) Was the lab manual clearly written
PART B (facility):
1) Did all the instruments work properly?
2) Were all the needed parts available?
3) Any other problems?
PART C (Lab Instructor):
1) Was the lab instructor helpful?
2) Did he/she know the experiment?
3) Was there any brief lecture in the lab?
4) Did the lab instructor know how to operate the instruments?
5) Any comments that may help the lab instructor improve? Your name (optional): Please return to your course instructor 28 APPENDIX
How to read Resistor Color Codes
First the code
Black Brown Red Orange Yellow Green Blue Violet Gray White
0 1 2 3 4 5 6 7 8 9 How to read the code
First find the tolerance band, it will typically be gold (5%) and sometimes silver (10%).
Starting from the other end, identify the first band  write down the number associated with that color;
in this case Blue is 6.
Now 'read' the next color, here it is red so write down a '2' next to the six. (you should have '62' so
far.)
Now read the third or 'multiplier' band and write down that number of zeros.
In this example it is two so we get '6200' or '6,200'. If the 'multiplier' band is Black (for zero) don't
write any zeros down.
If the 'multiplier' band is Gold move the decimal point one to the left. If the 'multiplier' band is
Silver move the decimal point two places to the left. If the resistor has one more band past the
tolerance band it is a quality band.
Read the number as the '% Failure rate per 1000 hour' This is rated assuming full wattage being
applied to the resistors. (To get better failure rates, resistors are typically specified to have twice the
needed wattage dissipation that the circuit produces) 1% resistors have three bands to read digits to
the left of the multiplier. They have a different temperature coefficient in order to provide the 1%
tolerance. 29 Examples
Example 1:
You are given a resistor whose stripes are colored from left to right as brown, black, orange, gold. Find the
resistance value.
Step One: The gold stripe is on the right so go to Step Two.
Step Two: The first stripe is brown which has a value of 1. The second stripe is black which has a value of 0.
Therefore the first two digits of the resistance value are 10.
Step Three: The third stripe is orange which means x 1,000.
Step Four: The value of the resistance is found as 10 x 1000 = 10,000 ohms (10 kilohms = 10 kohms).
The gold stripe means the actual value of the resistor mar vary by 5% meaning the actual value will be somewhere
between 9,500 ohms and 10,500 ohms. (Since 5% of 10,000 = 0.05 x 10,000 = 500) Example 2:
You are given a resistor whose stripes are colored from left to right as orange, orange, brown, silver. Find the
resistance value.
Step One: The silver stripe is on the right so go to Step Two.
Step Two: The first stripe is orange which has a value of 3. The second stripe is orange which has a value of 3.
Therefore the first two digits of the resistance value are 33.
Step Three: The third stripe is brown which means x 10.
Step Four: The value of the resistance is found as 33 x 10 = 330 ohms.
The silver stripe means the actual value of the resistor mar vary by 10% meaning the actual value will be between
297 ohms and 363 ohms. (Since 10% of 330 = 0.10 x 330 = 33)
Example 3:
You are given a resistor whose stripes are colored from left to right as blue, gray, red, gold. Find the resistance
value.
Step One: The gold stripe is on the right so go to Step Two.
Step Two: The first stripe is blue which has a value of 6. The second stripe is gray which has a value of 8. Therefore
the first two digits of the resistance value are 68.
Step Three: The third stripe is red which means x 100.
Step Four: The value of the resistance is found as 68 x 100 = 6800 ohms (6.8 kilohms = 6.8 kohms).
The gold stripe means the actual value of the resistor mar vary by 5% meaning the actual value will be somewhere
between 6,460 ohms and 7,140 ohms. (Since 5% of 6,800 = 0.05 x 6,800 = 340) 30 Resistor and capacitor values that are normally stocked in the lab. 31 32 33 ...
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This note was uploaded on 09/22/2010 for the course EEE 3123 taught by Professor Eel during the Spring '10 term at Florida State College.
 Spring '10
 Eel

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