Untitled - Qafqaz University

Untitled - Qafqaz University
Khalil Ismailov
ELECTRONICS
LABORATORY MANUAL
Qafqaz University Press
Baku, 2011
ELECTRONICS
LABORATORY MANUAL
Prepared by
Kh.A. Ismailov, Professor
Department of Computer Engineering,
Qafqaz University
Reviewed by
A.Z. Melikov, Professor
Associate Member of the National
Academy of Sciences of Azerbaijan Republic,
The Institute of Cybernetics of the National
Academy of Sciences of Azerbaijan Republic
Reviewed by
A.Z. Adamov, PhD
Department of Computer Engineering,
Qafqaz University
Design
Sahib Kazimov
Is printed as a publication of Qafqaz University by the
proposal of the Publishing Committee dated from 06.12.2010
(minute No 7) and decision of the Senate dated from
15.12.2010 (minute No Ç-QU-15000-000.100)
Book is printed by “Sharg-Garb” Publishing House.
Tel: (+994 12) 374 83 43, 374 75 62
Copyright  Qafqaz University, 2011
Copyright  Khalil Ismailov, 2011
Qafqaz University Press No: 45
Baku, 2011
CONTENTS
PREFACE
SAFETY
Introduction
Current Hazards and Voltage Safety Precautions
Neat Working Area
In Case of Electrical Shock
INSTRUCTIONS FOR ELECTRONICS LABORATORY
Organization
Purpose and Procedure
Grading
Equipment Handling
General Tips
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6
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7
7
8
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10
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EXPERIMENT 1. Oscilloscope and Function Generator Operation
EXPERIMENT 2. Diode Characteristics
EXPERIMENT 3. Half-Wave and Full-Wave Rectification
EXPERIMENT 4. Zener Diodes
EXPERIMENT 5. Light-Emitting Diodes
EXPERIMENT 6. Bipolar-Junction Transistor
EXPERIMENT 7. Junction Field-Effect Transistor
EXPERIMENT 8. Op-Amp Characteristics
EXPERIMENT 9. Linear Op-Amp Circuits
EXPERIMENT 10. Electronic Hobby Circuits
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38
55
69
78
94
109
120
133
REFERENCES
168
APPENDIX A Important electrical units, abbreviations and symbols
APPENDIX B Using the Metric System to Help Some Familiar Metrics
APPENDIX C Resistor Color Coding
APPENDIX D Capacitor Color Coding
APPENDIX E General Purpose NPN and PNP Transistors
APPENDIX F JFET Transistors
APPENDIX G Useful Electronics Sites
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171
173
174
177
179
PREFACE
The experiments in this laboratory course are designed to cover the
theoretical and analytical materials in “Electronics”. Each experiment begins
with a set of stated objectives, text references, and required equipment,
followed by a procedure for meeting each objective. The objective of the
experiments is to enhance the students’ understanding of important analytical
principles developed in this course by engaging them in the real-world
application of these principles in the laboratory. In addition to further develop
the students’ laboratory practice for experimentally testing and evaluating
electrical circuits.
Preparing the lab is very important as it will save time and allows
working more efficiently. The pre-lab includes reading the lab assignment in
advance, and doing the pre-lab assignment specific to each lab experiment.
All pre-lab assignments have to be handed in with the main lab report at the
beginning of the class.
The manual is designed as an individualized learning package and
involves the student in the activities of learning. Many illustrations and line
drawings are used to familiarize the student with circuit recognition and
analysis, since, this is an important part of being a good electronics
technician.
Each unit follows the same format so that the person using the book can
become accustomed to the learning procedure. The basic experiments are
given on how to test the device and verify its theory of operation. Fill-in
questions are given at the end of each experiment to emphasize the important
points gained from performing the experiment.
This manual contains several appendixes at the end. The students is
encouraged to become familiar with the contents of the appendixes early.
Appendix A covers descriptions of important electrical units, abbreviations
and symbols. Using the Metric System to Help Some Familiar Metrics is
provided in Appendix B.
The information about resistor and capacitor color coding is provided in
Appendices C and D.
Appendices E and F covers product descriptions and pin configuration of
general purpose NPN/PNP transistors and N-/P-channel FET transistors.
A list of useful electronics sites is provided in Appendix G.
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SAFETY
Introduction
The experiments in this manual do not use a voltage greater than 30V (or
±15V); therefore, the chance of getting an electrical shock is greatly reduced.
However, all voltages do have the potential to burn materials and start fires, to
destroy electronic components, and present hazards to the person performing
the operations. Common sense and an awareness of electrical circuits is
important whenever you are working on these experiments. Before actual
work is performed, sufficient instruction should be acquired in the proper use
and safety requirements of all electronic devices.
Current Hazards and Voltage Safety Precautions
It takes a very small amount of current to pass through the human body
from an electrical shock to injure a person severely or fatally. The 50-Hz
current values affecting the human body are as follows:
Current value
1 mA (0.001 A)
10 mA (0.01 A)
100 mA (0.1 A)
Over 100 mA
Effects
Tingling or mild sensation.
A shock of sufficient intensity to cause involuntary
control of muscles, so that a person cannot let go of an
electrical conductor.
A shock of this type lasting for 1 second is sufficient to
cause a crippling effect or even death.
An extremely severe shock that may cause ventricular
fibrillation, where a change in the rhythm of the
heartbeat causes death almost instantaneously.
The resistance of the human body varies from about 500,000 Ω when dry
to about 300 Ω when wet (including the effects of perspiration). In this case,
voltages as low as 30 V can cause sufficient current to be fatal (I=voltage /
wet resistance=30 V/300 Ω=100 mA).
Even though the actual voltage of a circuit being worked on is low
enough not to present a very hazardous situation, the equipment being used
to power and test the circuit (i.e., power supply, signal generator, meters,
oscilloscopes) is usually operated on 220 V AC. To minimize the chance of
getting shocked, a person should use only one hand while making voltage
measurements, keeping the other hand at the side of the body, in the lap, or
behind the body. Do not defeat the safety feature (fuse, circuit breaker,
interlock switch) of any electrical device by shorting across it or by using a
higher amperage rating than that specified by the manufacturer. These safety
devices are intended to protect both the user and the equipment.
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Neat Working Area
A neat working area requires a careful and deliberate approach when
setting it up. Test equipment and tools should be set out on the workbench in
a neat and orderly manner. Connecting wires from the test equipment to the
circuit under test should be placed so as not to interfere with testing
procedures.
Before power is applied to a circuit, the area around the circuit should be
cleared of extra wires, components, hand tools, and debris (cut wire and
insulation).
In Case of Electrical Shock
When a person comes in contact with an electrical circuit of sufficient
voltage to cause shock, certain steps should be taken as outlined in the
following procedure:
1. Quickly remove the victim from the source of electricity by means of a
switch, circuit breaker, pulling the cord, or cutting the wires with a wellinsulated tool.
2. It may be faster to separate the victim from the electrical circuit by using
a dry stick, rope, leather belt, coat, blanket, or any other nonconducting
material.
CAUTION: Do not touch the victim or the electrical circuit unless the
power is off.
3. Call for assistance, since other persons may be more knowledgeable in
treating the victim or can call for professional medical help while first aid
is being given.
4. Check the victim’s breathing and heartbeat.
5. If breathing has stopped but the victim's pulse is detectable, give mouthto-mouth resuscitation until medical help arrives.
6. If the heartbeat has stopped, use cardiopulmonary resuscitation, but only
if you are trained in the proper technique.
7. If both breathing and heartbeat have stopped, alternate between mouthto-mouth resuscitation and cardiopulmonary resuscitation (but only if you
are trained).
8. Use blankets or coats to keep the victim warm and raise the legs slightly
above head level to help prevent shock.
9. If the victim has burns, cover your mouth and nostrils with gauze or a
clean handkerchief to avoid breathing germs on the victim and then wrap
the burned areas of the victim firmly with sterile gauze or a clean cloth.
10. In any case, do not just stand there – do something within your ability to
give the victim some first aid.
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INSTRUCTIONS FOR
ELECTRONICS LABORATORY
Organization
The laboratory work is a group activity. Students will be divided into
groups of two or three. All members of a group are expected to be present and
participate in conducting an experiment with as much equal contribution as
possible. All members of a group are expected to come prepared, and
complete the work within the scheduled laboratory period with their
laboratory partners. No individual member and no individual group will be
allowed to do an experiment outside the scheduled times except under
extenuating circumstances and only with the consent of the instructor.
Purpose and Procedure
The purpose of this course is to cultivate in the student a degree of
independence in carrying out an engineering task. The burden (and reward) of
success is the student's, not the instructor’s.
The student will perform specific electronic experiments as indicated by
handouts for each experiment. These handouts are generally specific but leave
much room for independent approaches. In the lectures background and
motivating material and a certain degree of guidance for the experiments will
be given; but the exact experimental set-up or diagrams will not be given. This
is the responsibility of the student. The instructor (or the teaching assistant of
the laboratory session) may give a moderate degree of specific guidance,
mainly by asking the student pertinent questions to direct the student onto a
correct path. He will do this only after the student has demonstrated
substantial serious effort to solve the problem. The student should not expect
to receive from the lab instructor exact circuit diagrams. The instructor will,
however, point out errors in diagrams or hook-ups as far as this can
reasonably be done. The grade given to the student for the experiment will
partly depend on the degree of independence of the student. If everything else
fails, the instructor will provide a good diagram, but this will be done at a
severe penalty in the grading.
Contrary to popular belief, most of the work must be done by the student
before he or she comes to the laboratory. One should study the problems
using common sense and any required textbooks and/or reference books. One
must prepare a complete procedure for the experimental work including
alternatives and must know what components and equipment are needed and
allow for substitution if the first choice is not available. One must study the
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problem before coming to the laboratory so that the general trend of results is
anticipated. This will make it possible to recognize "nonsense" results and
correct the experimental procedure. Unnoticed wrong results will be
considered worse than incomplete results in the grading, since the theory and
the laboratory is available to the student to validate results.
Each student must have a laboratory manual. The manual will contain the
preliminary work done as well as the complete work plan for the experiment.
It will also contain every test and check made, all in-lab computations,
modifications of circuit or procedure, and results. The instructor may examine
the work done and grade the preliminary during the lab periods.
A concise, but complete, neatly prepared final report for each experiment
by each member of the group must be handed in to the instructor within one
week after the completion of the experiment. It is expected that the circuits,
design calculations and data to be the same for two reports written by the
members of the same group. But, this cannot be used to justify near identical
reports to be submitted. Particularly, discussions, comments, conclusions and
the overall style should reflect individual contribution and originality. A good
presentation is clear, concise, and informative. It makes good use of graphics,
has good writing style and presents ideas in a nice logical sequence.
Some longer experiments will be allowed to be completed in two weeks.
A quiz may be given at the beginning of each experiment. The instructor will
give some overall guidance at the beginning. The work plans will be checked
in the laboratory and graded.
In summary the student’s endeavors will include:
1. Preparation of work plans for each experiment based on independent
reading and analysis, and lecture suggestions.
2. Preparation for and taking of lab quizzes. (Note that preparation of a good
work plan will aid in quiz preparation.
3. Conducting of the actual experiments in the laboratory.
4. Preparation of a final report for each experiment.
Grading
Grades will be assigned over the following categories with the indicated
weights (approximately):
Lab reports:
25% Preliminary work/design
50% Experiment and participation
25% Discussions/Conclusions
NO LAB EXPERIMENT OR ITS REPORT MAY BE SKIPPED.
LATE REPORTS LOSE 50% PER WEEK, COMPOUNDED.
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Equipment Handling
Never take for granted that the equipment or components are in good
condition. Always check all equipment before you start the experiment. Make
certain the power supply has ripple free output voltage and that the
oscilloscope has the correct gain in the ranges of interest. Check all diodes
and transistors with an ohm-meter. Make sure resistors and potentiometers are
close to the indicated value. Make sure that capacitors are not shorted, nor
opened. In case of equipment failure, keep the malfunctioning equipment on
your bench; do not swap equipment from other benches. Equipment sets are
assigned to groups. Do not attempt to repair malfunctioning equipment. Do
not even replace fuses. Call the lab instructor/technician for appropriate
action.
General Tips
When something doesn’t work as you expect, be skeptical about all facets
of your design, fabrication and test of the circuit. Although test equipment
may fail from time to time, problems are almost always due to errors in
design, documentation or wiring; faulty components occasionally; or a
misunderstanding of how to use the test equipment. In the laboratory the
experimenter interacts with natural phenomena which tend to be brutally
honest and unforgiving in evaluating a poorly thought out experiment.
Group interactions can be difficult; but Engineering is inherently a
discipline requiring much team effort. Thus, the skills developed in working
effectively in a grouped environment are quite important. It is the
responsibility of each student to create an effective group where everyone
contributes substantially.
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EXPERIMENT
1
OSCILLOSCOPE and FUNCTION
GENERATOR OPERATION
OBJECTIVES
1.
2.
3.
4.
To understand the operation and use of an oscilloscope
To learn to measure DC and AC voltages with the oscilloscope
To use an oscilloscope to observe repetitive time varying waveforms
To use a function generator to create repetitive waveforms
BASIC INFORMATION
The Oscilloscope
The oscilloscope or “scope” as it is better known is one of the most
versatile pieces of laboratory test equipment (Fig. 1.1). It is really a type of
analog voltmeter with an arbitrary zero. It can read DC voltages as an offset
voltage and as well as AC voltages by displaying the true wave form. Most
modern oscilloscopes are capable of measuring AC signals over a wide range
of frequencies.
The heart of the oscilloscope is the cathode ray tube, which generates the
electron beam, accelerates the beam to a high velocity, deflects the beam to
create the image, and contains the phosphor screen where the electron beam
eventually becomes visible. The electrons are called cathode rays because
they are emitted by the cathode and this gives the oscilloscope its full name of
cathode ray oscilloscope (CRO) or cathode ray tube (CRT) oscilloscope (Fig.
1.2). The electron beam emitted by the heated cathode at the rear end of the
tube is accelerated and focused by one or more anodes, and strikes the front
of the tube, producing a bright spot on the phosphorescent screen.
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Fig. 1.1. Cathode Ray Oscilloscope
The heart of the oscilloscope is the cathode ray tube, which generates the
electron beam, accelerates the beam to a high velocity, deflects the beam to
create the image, and contains the phosphor screen where the electron beam
eventually becomes visible. The electrons are called cathode rays because
they are emitted by the cathode and this gives the oscilloscope its full name of
cathode ray oscilloscope (CRO) or cathode ray tube (CRT) oscilloscope (Fig.
1.2). The electron beam emitted by the heated cathode at the rear end of the
tube is accelerated and focused by one or more anodes, and strikes the front
of the tube, producing a bright spot on the phosphorescent screen.
The electron beam is bent, or deflected, by voltages applied to two sets of
plates fixed in the tube. The horizontal deflection plates, or X-plates produce
side to side movement. As you can see, they are linked to a system block
called the time base. This produces a sawtooth waveform. During the rising
phase of the sawtooth, the spot is driven at a uniform rate from left to right
across the front of the screen. During the falling phase, the electron beam
returns rapidly from right or left, but the spot is “blanked out” so that nothing
appears on the screen.
Although the oscilloscope can eventually be used to display practically
any parameter, the input to the oscilloscope is voltage. In this way, the time
base generates the X-axis of the V/t graph. The general laboratory oscilloscope
can accept as low as a few millivolts per centimeter of deflection up to
hundred of volts using the built-in attenuator and external probes.
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TIME/DIV
X-POS
Time base waveform
Spot move
across screen
Y
0
t
Spot
Spot blanked out
during flyback
Trigger
Time base
Heater
CH1
SIGNAL INPUT
AC/DC
switch
Cathode Anodes
Y-amplifier
Signal waveform
Y-plates
X-plates
Cathode
ray tube
Y
0
Electron
beem
t
VOLTS/DIV
SCREEN
Y-POS
Fig. 1.2. Cathode Ray Oscilloscope block-diagram
The slope of the rising phase varies with the frequency of the sawtooth
and can be adjusted, using the TIME/DIV control, to change the scale of the Xaxis. Dividing the oscilloscope screen into squares allows the horizontal scale
to be expressed in seconds, milliseconds or microseconds per division (s/DIV,
ms/DIV, µs/DIV). Alternatively, if the squares are 1 cm apart, the scale may be
given as s/cm, ms/cm or µs/cm.
The vertical input also will have a switch for AC or DC input signals.
When the AC/DC switch is in the DC position, the probe is connected directly
to the Y-amplifier. When the switch is in the AC position, there is a coupling
capacitor between the probe and the amplifiers. The reason to allow the
measurement of low-level AC signals which may be on the same wire as a
high-level DC voltage. If the probe is connected directly to the amplifiers, the
scope trace moves on the scale an amount equal to the voltage applied. If this
voltage is a high voltage, say 100 V the vertical attenuator must be set to an
insensitive position in order for the trace not to be deflected beyond the
viewable portion of the screen. With the vertical sensitivity thus set, a small
AC signal on the same wire could not be measured, when the vertical input
switch is in the AC position, a capacitor blocks the direct current from
reaching the amplifiers. With the direct current blocked, the vertical sensitivity
can be set so the AC signal can be easily seen and measured.
The Y-amplifier is linked in turn to a pair of Y-plates so that it provides the
Y-axis of the V/t graph. The overall gain of the Y-amplifier can be adjusted,
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using the VOLTS/DIV control, so that the resulting display is neither too small
nor too large, but fits the screen and can be seen clearly. The vertical scale is
usually given in V/DIV or mV/DIV.
The trigger circuit is used to delay the time base waveform so that the
same section of the input signal is displayed on the screen each time the spot
moves across. The effect of this is to give a stable picture on the oscilloscope
screen, making it easier to measure and interpret the signal.
Changing the scales of the X-axis and Y-axis allows many different signals
to be displayed. Sometimes, it is also useful to be able to change
the positions of the axes. This is possible using the X-POS and Y-POS controls.
For example, with no signal applied, the normal trace is a straight line across
the centre of the screen. Adjusting Y-POS allows the zero level on the Y-axis
to be changed, moving the whole trace up or down on the screen to give an
effective display of signals like pulse waveforms which do not alternate
between positive and negative values.
A dual trace oscilloscope can display two traces on the screen, allowing
you to easily compare the input and output of an amplifier for example. The
dual trace oscilloscope provides for amplification and display of two signals at
the same time, thereby permitting direct comparison of the signals on the CRT
screen (measure the phase displacement of two waveforms, and so on).
Front Panel Controls Front panel controls permit you to control the
operation of the oscilloscope. They may be grouped functionally as:
Main Oscilloscope Controls According to Function
Display
Intensity
Focus
Beam Finder
Vertical
Coupling (AC-Ground-DC)
Volts/Div
Y-position
Channel Select
Magnification
Cal (Calibrated)
Horizontal
Time base (Sec/Div)
X-position
Magnification
Cal (Calibrated)
Triggering
Coupling
Source
Level
Slope
Mode
The above function set is summarized for a typical oscilloscope only. The
oscilloscope in the laboratory that you will be using may have more functions.
For detail operation of the oscilloscope, you should refer to the user’s manual
of the oscilloscope.
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Connecting the oscilloscope to the circuit under test
The input impedance of an oscilloscope is rather high, being on the order
of 1 MΩ, which is desirable for measuring voltages in high impedance
circuits. The attenuator sets the sensitivity of the oscilloscope in the common
1-2-5 sequence. As an example, the input attenuator could provide for 10, 20,
50, 100, 200 mV, etc., per centimeter. The input attenuator must provide the
correct 1-2-5 sequence attenuation while maintaining a constant input
impedance, as well as maintaining both the input impedance and attenuation
over the frequency range for which the oscilloscope was designed.
The oscilloscope is connected to the circuit under test by means of a
probe (or set of probes) as illustrated in Fig. 1.3. The probe includes a
measurement tip and a ground clip and connects to the oscilloscope by a BNC
connector via a flexible, shielded cable which is grounded at the oscilloscope.
This ground serves as the reference point with respect to which all signals are
measured. The shield helps guard electrical noise pick up.
Voltage Measurements A screen is divided into centimeter divisions in
the vertical and horizontal directions. The vertical sensitivity is provided (or
set) in volts/cm, while the horizontal sensitivity is provided (or set) in time
(s/cm). The magnitude of the signal can be determined from the following
equation:
Signal voltage Vs = voltage sensitivity (V/cm) × deflection (cm)
If a particular signal occupies 6 vertical centimeters and the vertical sensitivity is 5 mV/cm, signal voltage Vs = (5 mV/cm) (6 cm) = 30 mV.
Fig. 1.3. Connection of the oscilloscope to the circuit under test
Sometimes an attenuator probe is used to expand the range of the scope.
This probe has a high-value resistor in it which acts as a voltage divider with
the scope input resistance. As a result, whatever voltage is read on the scope
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graticule must be multiplied by 10. Such a probe is called a “times 10,” or
×10, probe.
The simplest AC signal is the sine wave and you should use this function
as your first AC source. When this signal is connected to the oscilloscope, you
can see that you can easily measure the peak AC voltage, Vp, which is defined
as the voltage measured from the center or zero position to the peak (see Fig.
1.4). There are several other voltages that can also be measured. The peak-topeak voltage, Vp-p, is the voltage measured from the crest of one cycle to the
bottom trough of the cycle or peak-to-peak. Finally, the most common voltage
is the rms or root-mean-square voltage, Vrms. It is equal to the peak-to-peak
value divided by (2×1.414). For the sine wave only:
Vp = Vp − p / 2 = 2Vrms
A one volt rms waveform has the same heating value as a one volt DC
signal.
Time Period Measurements Time is shown on the horizontal X-axis and
the scale is determined by the TIMEBASE (TIME/DIV) control. The time period
(often just called period) is the time for one cycle of the signal. The frequency
is the number of cycles per second, frequency = 1/time period.
v
Vp
Vrms
0
t
Vp-p
T
Fig. 1.4. Measurement of voltages on an oscilloscope
Ensure that the variable timebase control is click-stopped fully clockwise
before attempting to take a time reading.
Time = distance in cm × time/cm
For example, if time period=4.0cm×5 ms/cm=20ms then frequency=
=1/time period=1/20ms=50 Hz.
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Functional descriptions of an oscilloscope OS-5020:
Coupling (AC-GND-DC): Permits selection of coupling of the input
channel.
When set to DC, the entire signal (AC plus any DC components) is
displayed.
When set to AC, DC signals are blocked by a capacitor and only AC
is displayed.
When set to ground, the input channel is isolated from the input
source and is grounded internally.
VOLTS/DIV: This is the scope’s vertical sensitivity control. It is a
calibrated control that establishes how many volts each major vertical scale
division represents. For example, when it is set for 1 V/DIV, each grid line
represents 1 volt. Each channel has its own independent VOLTS/DIV control.
CAL.: This is the fine adjust control, usually located in the inner of the
VOLTS/DIV knob. When this knob is turned to the fully clockwise direction,
it is at the calibrated location (the normal position of this knob) for the outer
knob setting, i.e., the vertical scale of the scope is defined by the VOLTS/DIV
knob. When the CAL. knob is turned away from the calibrated position, the
waveform displayed in the scope will start to be attenuated.
Vertical POSITION: This is the vertical position control. Each channel
has its own control. It moves the trace up or down for easier observation. It is
not calibrated.
Channel Select: Permits displaying CH1, CH2, both channels, their sum
or difference.
Timebase (V MODE): This is a calibrated control that selects how many
seconds each major horizontal division represents. It is calibrated in s, ms,
and µs. One control handles all channels. There is also CAL. knob for the
time base. The CAL. knob is located at the inner of the TIME/DIV knob. Its
operation is similar to that of the previous one for the VOLTS/DIV.
Magnification: For both CAL. knobs of the VOLTS/DIV and TIME/DIV,
the CAL. Knob also acts as the magnification switch. The magnification is ×5
or ×10 with the knob pulled out.
Horizontal POSITION: Positions the trace horizontally. One control
handles all channels.
Trigger Source: Selects the trigger source, e.g., CH1, CH2, an external
trigger, or the AC power line.
Trigger Level: Permits you to adjust the point on the trigger source
waveform where you like the triggering to start.
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Trigger Slope: Selects whether the scope is to trigger on the positive or
negative slope of the trigger source waveform.
Trigger Mode: Modes include
AUTO – the sweep always occurs, even with no trigger present,
NORMAL – a trigger must be present, and
SINGLE SWEEP – a trigger is required but only one sweep results.
INTENSITY: Adjusts the intensity of the displayed beam.
FOCUS: Adjusts the sharpness of the displayed beam.
AUTO: Some oscilloscopes with electronic control are fitted with a
button which automatically selects an appropriate timebase, triggering mode
and horizontal gain.
Function Generator
The function generator is a supply that typically provides a sinusoidal,
square-wave, and triangular waveforms for a range of frequencies and
amplitudes. Although the frequency of the function generator can be set by
the dial position and appropriate multiplier, the oscilloscope can be used to
precisely set the output frequency. The scope can also be used to set the
amplitude of the function generator since most function generators simply
have an amplitude control with no level indicators.
The model FG-8002 (Fig. 1.5) is an advanced function generator which
provides functions of function generator, pulse generator and sweep oscillator
including following versatile features:
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18
Wide frequency range from 0.02 Hz to 2 MHz.
Versatile waveforms are selectable in sine wave, square wave. Triangle
wave and pulse wave, etc.
TTL level square wave output is available for signal source for digital
circuit experiments.
Variable symmetry to generate sawtooth and pulse waveform
Frequency of output signal can be controlled by applying voltage from
0 to +10 V to VCF IN connector.
The linear sweep function provides SWEEP FUNCTION CONTROL
from 1:1 to 100:1.
DC voltage from 0 to +10 V can be overload upon output waveform
Maximum attenuation over 40 dB.
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Fig. 1.5 Function Generator
SUMMARY
The most common scope in use today is the triggered-sweep scope.
Older scopes were the recurrent sweep type.
2. The typical scope has four sections: vertical; horizontal; trigger, or
sync; and display.
3. The vertical section of the scope conditions the input and causes the
beam in the CRT to be deflected vertically.
4. The horizontal section of the scope controls the horizontal sweep of
the CRT electron beam. It causes the beam to sweep at an accurate
rate, so frequency can be calculated from the sweep time.
5. The trigger section of the scope controls how the beam is synchronized
with the incoming signal to cause the waveform to be stable.
6. The display section of the scope controls brightness, focus, etc.
7. The scope has controls to allow adjustment of vertical sensitivity,
vertical and horizontal beam position, etc.
8. The AC-DC switch allows the display of either AC or DC signals.
9. The function generator typically provides a sinusoidal, square-wave, and
triangular waveform for a range of frequencies and amplitudes.
10. Advanced function generator provides functions of function generator,
pulse generator and sweep oscillator.
1.
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SELF-TEST
Check your understanding of the introductory information by answering
the following questions.
1. What is the purpose of the horizontal time-base section?
2. Why is the AC-DC switch setting important when you are making lowlevel AC measurements?
3. The term attenuate means what?
4. What are the four sections of the scope?
5. What kind of waveforms is provided by the function generator?
6. What are the functions of the advanced function generators?
MATERIALS REQUIRED
•
•
•
Oscilloscope (OS-5020)
Variable DC power supply (GP-4303TP)
Function generator (FG-8002)
PROCEDURE
Setting up an oscilloscope
Before placing the instrument in use, set up and check the instrument as
follows:
1.
20
Set the following controls as indicated.
POWER Switch
INTEN Control
FOCUS Control
AC/GND/DC Switch
VOLTS/DIV Switch
×5MAG Switch
Vertical POSITION Controls
INV Switch
VARIABLE Controls
V MODE Switch
TIME/DIV Switch
VARIABLE Control
Horizontal POSITION Control
×10MAG Switch
OFF (released)
Mid rotation
Mid rotation
DC
10 mV
×1
Mid rotation
Norm
Fully CCW
CH1
1 ms
CAL
Mid rotation
×1
Elecrtronics
Trigger MODE Switch
Trigger SOURCE Switch
Trigger LEVEL Control
SLOPE Switch
AUTO
VERT
Mid rotation
Button out
2.
Press the POWER Switch.
The POWER lamp should light immediately. About 30 seconds later,
rotate the INTEN. Control clockwise until the trace appears on the CRT
screen. Adjust brightness to your liking.
3.
Turn the FOCUS Control for a sharp trace.
4.
Turn the CH1 Vertical POSITION Control to move the CH1 trace to the
center horizontal graticule line.
5.
See if the trace is precisely parallel with the graticule line.
6.
Turn the Horizontal POSITION Control to align the left edge of the trace
with the left most graticule line.
7.
Set one of the supplied probes (Fig. 1.6) for ×10 attenuation. Then,
connect its BNC end to the CH1 or X IN Connector.
Fig. 1.6. Probe
Scope probes are available with ×1 attenuation (direct connection) and
×10 attenuation. The ×10 attenuator probes increase the effective input
impedance of the probe/scope combination to 10 megohms shunted by a few
picofarads, the reduction in input capacitance is the most important reason for
using attenuator probes at high frequencies, where capacitance is the major
factor in loading down a circuit and distorting the signal. When ×10
attenuator probes are used, the scale factor (VOLTS/DIV switch setting) must
be multiplied by ten.
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Khalil Ismailov
Single-trace Operation The OS-5020 is set up for single-trace operation
as follows:
1. Set the following controls as indicated below. Note that the trigger source
selected (CH1 or CH2 SOURCE) must match the single channel selected.
(CH1 or CH2 V-MODE)
POWER switch
ON (pushed in)
AC/GND/DC switches
AC
Vertical POSITION controls
Mid rotation
VARIABLE controls
Fully CW
V MODE switch
CH1 (CH2)
VARIABLE control
CAL
Trigger MODE switch
AUTO
Trigger SOURCE switch
VERT
Trigger LEVEL control
Mid rotation
2.
3.
4.
5.
Use the corresponding Vertical POSITION control or to set the trace near
mid screen.
Connect the signal to be observed to the corresponding IN connector and
adjust the corresponding VOLTS/DIV switch or so the displayed signal is
totally on screen.
CAUTION>
Do not apply a signal greater than 400 V (DC + peak AC)
Set the TIME/DIV switch so the desired number of signal cycles are
displayed. Adjust the Trigger LEVEL control if necessary for a stable
display.
If the signal you wish to observe is either DC or low enough in frequency,
the AC coupling will attenuate or distort the signal. So, flip the AC/GND/DC
switch or to DC.
Dual-trace Operation Dual trace operation is the major operating mode
of the OS-5020. The setup for dual trace operation is identical to that of single
trace operation with the following exceptions:
1. Set the V MODE switch to either DUAL. Select ALT for relatively high
frequency signals (TIME/DIV switch set to 0.5 ms or faster). Select CHOP
for relatively low frequency signals (TIME/DIV switch set to 1 ms or
slower).
2. If both channels are displayed in signals of the same frequency, set the
Trigger SOURCE switch to the channel having the steepest-slope waveform.
If the signals are different but harmonically related, trigger from the channel
carrying the lowest frequency. Also, remember that if you disconnect the
channel serving as the trigger source, the entire display will free run.
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Setting up a Function Generator
1.
2.
3.
4.
5.
6.
7.
8.
9.
Pressing POWER Switch turns on power. POWER Lamp light up when
power is on.
Connect BNC end of the clip probe to the OUTPUT 50 Ω BNC socket.
The lead is connected with a push and twist action, to disconnect you
need to twist and pull.
Push on of three knobs of FUNCTION Selector to get a desired waveform
out of sine wave, triangle wave and square wave.
Amplitude of output signal can be controlled by AMPLITUDE/PULL–20
dB knob. Maximum attenuation is more than 20 dB when the knob is
rotated fully counterclockwise. Pulling this knob makes attenuation of 20
dB, so the output signal can be attenuated by 40 dB when this is pulled
and rotated fully counterclockwise.
Frequency range (Seven ranges: 1 – 0.02 Hz to 2 Hz, 10 – 2 Hz to 20
Hz, 100 – 20 Hz to 200 Hz, 1k – 200 Hz to 2 kHz, 10k – 2 kHz to 20
kHz, 100k – 20 kHz to 200 kHz, 1M – 200 kHz to 2 MHz,) is selected
by FREQUENCY RANGE Selector. Output frequency within the selected
range is varied by the Frequency Dial potentiometer.
Sweep width is controlled by SWEEP WIDTH/PULL ON Control. Pulling
the knob selects internal sweep and rotating it controls sweep width.
Rotate it counterclockwise to get a minimum sweep width (1:1) and
rotate it clockwise to get a maximum sweep width (100:1). To get a
maximum sweep width, set the frequency dial to minimum scale (below
0.2 scale).
Sweep rate (sweep frequency) of internal sweep oscillator is controlled by
SWEEP RATE Control.
Symmetry (duty cycle) of output signal waveform within range of 10:1 to
1:10 is controlled by SYMMETRY Control.
The DC OFFSET control knob may be used to offset the waveform above
or below ground (0 volts) by a DC voltage in the range ±10 volts. To
adjust the DC level pull out the OFFSET control knob then turn slowly
CW (positive volts) or CCW (negative volts). If the OFFSET knob is pushed
in, there is no DC level, but only AC voltage exists in the output signal.
Measurements
1.
2.
Plug the power cable of the oscilloscope into the socket outlet in the
bench.
Practice setting up the scope to get a trace on the screen. Move the trace
around. Work with all the controls until you understand their functions.
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Khalil Ismailov
3.
4.
5.
6.
Rotate the focus and intensity controls to get a sharply focused trace at a
comfortable viewing level.
Connect a probe to CH1 and set the channel selector to CH1 and use a
×1 probe. Set the TRIGGER to AUTO.
Flip the AC-GND-DC coupling switch to GND (ground) and center the
trace.
Connect the output of the variable DC power supply to the input of the
oscilloscope as shown in Fig. 1.7.
Trace
+V
CH1
Variable DC
power supply
–V
Ground
clip
Probe
Fig. 1.7. Measuring DC voltage
7.
8.
9.
Set the vertical attenuator to measure 0.5 V/cm. Make sure the vertical
attenuator vernier (fine-adjust) control is in the CAL. position. The AC-DC
switch should be set to DC. Measure the voltage of a 1-, 1.5-, and 2-V
source (obtained from the variable power supply).
Connect the probe as in Fig. 1.7 and set VIOLTS/DIV to 1 V. Set the
output of the variable DC power supply to 2 V and note the beam
deflection on the screen. From the deflection, compute the measured
voltage. Fill in the table after doing step 9.
Change VOLTS/DIV to 2 V, set the output of the variable DC power
supply to 5 V and note the position of the trace. Make similar adjustments
and fill in the following table.
Input
Voltage
2V
5V
15 V
10 V
15 V
22.5 V
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Probe
Volts/Div Setting
×1
×1
×1
×10
×10
×10
1V
2V
5V
Deflection
Oscilloscope Voltage Value
Elecrtronics
10. Replace the variable DC power supply with a function generator as
shown in Fig. 1.8. Connect the CH 1 input of the oscilloscope to 50 Ω
output of the function generator using a BNC-BNC lead (Fig. 1.9). Set
input coupling on the oscilloscope to ground and center the trace.
Change the input coupling to AC.
Trace
Oscilloscope
Output
Function
Generator
Ground
CH1
Ground
clip
Probe
Fig. 1.8. Measuring AC voltage
11. Set the function generator to 100 Hz. Now adjust it to display one, then
two, and then four cycles of signal. What were your horizontal time-base
settings? ___________________ .
Use the trigger controls to cause the waveforms to move and then to be
stationary (synchronized).
12. Set signal generator to any frequency. Set the vertical attenuator to 0.5
V/cm. Be sure the vertical attenuator vernier control is in the CAL.
position. Measure the voltage of a 1-, 1.5-, and 2-V peak-to-peak (p-p)
signal.
13. Connect the function generator to one of the inputs of the oscilloscope.
Set the vertical attenuator to 10 V/cm and AC-DC switch to DC position.
Switch the function generator on and pull out its DC OFFSET control
knob then turn slowly CW (positive volts) or CCW (negative volts).
What do you observe? ___________________________________________
_______________________________________________________________.
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Khalil Ismailov
OSCILLOSCOPE INPUT
BNC Socket
BNC plug
CH1
FUNCTION GENERATOR
50 Ω OUTPUT
Push and rotate
Push and rotate
Fig. 1.9. BNC-BNC lead
14. Flip the AC-DC switch to AC.
What happens?_________________________________________________
______________________________________________________________.
15. Set the function generator to a 2 kHz sine wave. On the oscilloscope, set
the VOLTS/DIV switch to 1 V, the Trigger to positive slope, and the time
base to 0.1 ms/Div.
16. Adjust the output voltage of the generator until you get a nicely sized sine
wave on the screen. Record the waveform in Fig. 1.10. Set the Trigger to
negative slope and record the waveform in Fig. 1.11. The peak to peak
voltage is: ________ V.
17. Set the frequency of the generator to 500 Hz and change the time base to
get 2 cycles on the screen (actually a bit more than two). Record the
waveform and the time base setting in Fig. 1.12.
18. Set the waveform of the generator to square wave and complete Figs.
1.13 and 1.14.
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Elecrtronics
Volts/Div =
Time base =
Volts/Div =
Fig. 1.10. Positive trigger
Volts/Div =
Time base =
Fig. 1.11. Negative trigger
Time base =
Fig. 1.12. Waveform recording
Volts/Div =
Time base =
Fig. 1.13. Positive trigger
Volts/Div =
Time base =
Fig. 1.14. Negative trigger
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Khalil Ismailov
QUESTIONS
1.
2.
3.
Is the time-base setting important when you are measuring direct current?
Explain.
How the magnitude of the signal is determined when you take
measurements of voltage from the screen?
If the vertical sensitivity is increased, it takes more signal to deflect the
beam (true/false).
Answers to Self-Test
1.
2.
3.
4.
5.
6.
28
To make the beam sweep across the CRT at a regular, predictable rate.
This, in turn, allows for accurate frequency measurements.
If there is any direct current on the same line with the low-level
alternating current and the scope is set in the DC position, the trace may
be detected off the screen. To keep the trace on the screen, the vertical
attenuator must be set so insensitively as to make the low-level alternating
current immeasurable.
To make smaller.
Vertical, horizontal, sync, and display.
Sinusoidal, square-wave, and triangular waveforms for a range of
frequencies and amplitudes.
Function generator, pulse generator and sweep oscillator.
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