Experiments in Electronics Fundamentals and Electric Circuits
Fundamentals To Accompany Floyd, Electronics Fundamentals and Electric
Circuit Fundamentals by David Buchla (z-lib.org)
Introduction to the Student
Preparing for Laboratory Work
The purpose of experimental work is to help you gain a better
understanding of the principles
of electronics and to give you experience with instruments and methods
used by technicians
and electronic engineers. You should begin each experiment with a clear
idea of the purpose
of the experiment and the theory behind the experiment. Each experiment
requires you to use
electronic instruments to measure various quantities. The measured data
are to be recorded,
and you need to interpret the measurements and draw conclusions about
your work. The
ability to measure, interpret, and communicate results is basic to
electronic work.
Preparation before coming to the laboratory is an important part of
experimental work.
You should prepare in advance for every experiment by reading the
Reading, Objectives, and
Summary of Theory sections before coming to class. The Summary of
Theory is not intended
to replace the theory presented in the text—it is meant only as a short
review to jog your
memory of key concepts and to provide some insight to the experiment.
You should also look
over the Procedure for the experiment. This prelab preparation will
enable you to work
efficiently in the laboratory and enhance the value of the laboratory
time.
This laboratory manual is designed to help you measure and record data
as efficiently
as possible. Techniques for using instruments are described in many
experiments. Data tables
are prepared and properly labeled to facilitate recording. Plots are
provided where necessary.
You will need to interpret and discuss the results in the section
titled Conclusion and answer
the Evaluation and Review Questions. The Conclusion to an experiment is
a concise
statement of your key findings from the experiment. Be careful of
generalizations that are not
supported by the data. The conclusion should be a specific statement
that includes important
findings with a brief discussion of problems, or revisions, or
suggestions you may have for
improving the circuit. It should directly relate to the objectives of
the experiment. For
example, if the objective of the experiment is to use the concept of
equivalent circuits to
simplify series-parallel circuit analysis (as in Experiment 10), the
conclusion can refer to the
simplified circuit drawings and indicate that these circuits were used
to compute the actual
voltages and currents in the experiment. Then include a statement
comparing the measured
and computed results as evidence that the equivalent circuits you
developed in the
experiment were capable of simplifying the analysis.
The Laboratory Notebook
Your instructor may assign a formal laboratory report or a report may
be assigned in the
section titled For Further Investigation. A suggested format for formal
reports is as follows:
1. Title and date.
2. Purpose: Give a statement of what you intend to determine as a
result
of the investigation.
3. Equipment and materials: Include a list of equipment model and
serial
numbers that can allow retracing if a defective or uncalibrated piece
of equipment
was used.
4. Procedure: Give a description of what you did and what measurements
you
made.
5. Data: Tabulate raw (unprocessed) data; data may be presented in
graph
form.
6. Sample calculations: Give the formulas that you applied to the raw
data
to transform them to processed data.
7. Conclusion: The conclusion is a specific statement supported by the
experimental
data. It should relate to the objectives for the experiment as
described earlier. For
example, if the purpose of the experiment is to determine the frequency
response of a
filter, the conclusion should describe the frequency response or
contain a reference to
an illustration of the response.
Graphing
A graph is a pictorial representation of data that enables you to see
the effect of one variable
on another. Graphs are widely used in experimental work to present
information because they
enable the reader to discern variations in magnitude, slope, and
direction between two
quantities. In this manual, you will graph data in many experiments.
You should be aware of the following terms that are used with graphs:
abscissa: the horizontal or x-axis of a graph. Normally the independent
variable is plotted along the abscissa.
dependent variable: a quantity that is influenced by changes in another
quantity (the independent variable).
graph: a pictorial representation of a set of data constructed on a set
of coordinates that are drawn at right angles to each other. The graph
illustrates one
variable's effect on another.
independent variable: the quantity that the experimenter can change.
ordinate: the vertical or y-axis of a graph. Normally the dependent
variable is plotted along the abscissa.
scale: the value of each division along the x- or y-axis. In a linear
scale, each division has equal weight. In a logarithmic scale, each
division represents the same
percentage change in the variable.
The following steps will guide you in preparing a graph:
Determine the type of scale that will be used. A linear scale is the
most frequently used and will be discussed here. Choose a scale factor
that enables all
of the data to be plotted on the graph without being cramped. The most
common scales
are 1, 2, 5, or 10 units per division. Start both axes from zero unless
the data
covers less than half of the length of the coordinate.
Number the major divisions along each axis. Do not number each small
division as it will make the graph appear cluttered. Each division must
have equal
weight. Note: The experimental data is not used to number the divisions.
Label each axis to indicate the quantity being measured and the
measurement units. Usually, the measurement units are given in
parentheses.
Plot the data points with a small dot with a small circle around each
point. If additional sets of data are plotted, use other distinctive
symbols
(such as triangles) to identify each set.
Draw a smooth line that represents the data trend. It is normal
practice to consider
data points but to ignore minor variations due to experimental errors.
(Exception: calibration curves and other discontinuous data are
connected
"dot-to-dot.
Title the graph, indicating with the title what the graph represents.
The completed graph should be self-explanatory.
Safety in the Laboratory
The experiments in this lab book are designed for low voltages to
minimize electric shock hazard; however, never assume that electric
circuits are safe. A
current of a few milliamps through the body can be lethal. In addition,
electronic laboratories
often contain other hazards such as chemicals and power tools. For your
safety, you should
review laboratory safety rules before beginning a course in
electronics. In particular,
you should
Avoid contact with any voltage source. Turn off power before working on
circuits.
Remove watches, jewelry, rings, and so forth before working on
circuits—even those circuits with low voltages—as burns can occur.
Know the location of the emergency power-off switch.
Never work alone in the laboratory.
Keep a neat work area and handle tools properly. Wear safety goggles or
gloves when required.
Ensure that line cords are in good condition and grounding pins are not
missing or bent. Do not defeat the three-wire ground system in order to
make
"floating" measurements.
Check that transformers and instruments that are plugged into utility
lines are properly fused and have no exposed wiring. If you are not
certain about
procedure, check with your instructor first.
Report any unsafe condition to your instructor.
Be aware of and follow laboratory rules.
Experiments in Digital Fundamentals,
10th Edition by David M. Buchla
(z-lib.org)
Introduction to the Student
Circuit Wiring
An important skill needed by electronics technicians is that of
transforming circuit drawings into working prototypes. The circuits in
this manual can be constructed on solderless protoboards
(“breadboards”) available at Radio Shack and other suppliers of
electronic equipment. These boards use #22- or #24-gauge solid core
wire, which should have 3/8 inch of the insulation stripped from the
ends. Protoboard wiring is not difficult, but it is easy to make a
wiring error that is time-consuming to correct. Wires should be kept
neat and close to the board. Avoid wiring across the top of integrated
circuits (ICs) or using wires much longer than necessary. A circuit
that looks like a plate of spaghetti is difficult to follow and worse
to troubleshoot.
One useful technique to help avoid errors, especially with larger
circuits, is to make a wire list. After assigning pin numbers to the
ICs, tabulate each wire in the circuit, showing where it is to be
connected and leaving a place to check off when it has been installed.
Another method is to cross out each wire on the schematic as it is
added to the circuit. Remember the power supply and ground connections,
because they frequently are left off logic drawings. Finally, it is
useful to “daisy-chain,” in the same color, signal wires that are
connected to the same electrical point. Daisy-chaining is illustrated
in Figure 1-1.
Troubleshooting
When the wiring is completed, test the circuit. If it does not work,
turn off the power and recheck the wiring. Wiring, rather than a faulty
component, is the more likely cause of an error. Check that the proper
power and ground are connected to each IC. If the problem is electrical
noise, decoupling capacitors between the power supply and ground may
help. Good troubleshooting requires the technician to understand
clearly the purpose of the circuit and its normal operation. It can
begin at the input and proceed toward the output; or it can begin at
the output and proceed toward the input; or it can be done by
half-splitting the circuit. Whatever procedure you choose, there is no
substitute for understanding how the circuit is supposed to behave and
applying your knowledge to the observed conditions in a systematic way.
The Laboratory Notebook
Purpose of a Laboratory Notebook
The laboratory notebook forms a chronologic record of laboratory work
in such a manner that it can be reconstructed if necessary. The
notebook is a bound and numbered daily record of laboratory work. Data
are recorded as they are observed. Each page is dated as it is done and
the signature of the person doing the work is added to make the work
official; laboratory notebooks may be the basis of patent applications
or have other legal purposes. No pages are left blank and no pages may
be removed.
General Information
The format of laboratory notebooks may vary; however, certain
requirements are basic to all laboratory notebooks. The name of the
experimenter, date, and purpose of the experiment are entered at the
top of each page. All test equipment should be identified by function,
manufacturer, and serial number to facilitate reconstruction of the
experiment. Test equipment may be identified on a block diagram or
circuit drawing rather than an equipment list. References to any books,
articles, or other sources that were used in preparing for the
experiment are noted. A brief description of the procedure is
necessary. The procedure is not a restatement of the instructions in
the experiment book but rather is a concise statement about what was
done in the experiment.
Recording of Data
Data taken in an experiment should be directly recorded in tabular form
in the notebook. Raw (not processed) data should be recorded. They
should not be transcribed from scratch paper. When calculations have
been applied to data, a sample calculation should be included to
indicate clearly what process has been applied to the raw data. If an
error is made, a single line should be drawn through the error with a
short explanation.
Graphs
A graph is a visual tool that can quickly convey to the reader the
relationship between variables. The eye can discern trends in magnitude
or slope more easily from graphs than from tabular data. Graphs are
constructed with the dependent variable plotted along the horizontal
axis (called the abscissa) and the independent variable plotted along
the vertical axis (called the ordinate). A smooth curve can be drawn
showing the trend of the data. It is not necessary to connect the data
points (except in calibration curves). For data in which one of the
variables is related to the other by a power, logarithmic (log) scales
in one or both axes may show the relationship of data. Log scales can
show data over a large range of values that will not fit on ordinary
graph paper. When you have determined the type of scale that best shows
the data, select numbers for the scale that are easily read. Do not use
the data for the scale; rather, choose numbers that allow the largest
data point to fit on the graph. Scales should generally start from zero
unless limitations in the data preclude it. Data points on the graph
should be shown with a dot in the center of a symbol such as a circle
or triangle. The graph should be labeled in a self-explanatory manner.
A figure number should be used as a reference in the written
explanation.
Schematics and Block Diagrams
Schematics, block diagrams, waveform drawings, and other illustrations
are important tools to depict the facts of an experiment. Experiments
with circuits need at least a schematic drawing showing the setup and
may benefit from other illustrations depending on your purpose.
Usually, simple drawings are best; however, sufficient detail must be
shown to enable the reader to reconstruct the circuit if necessary.
Adequate information should be contained with an illustration to make
its purpose clear to the reader.
Results and Conclusion
The section that discusses the results and conclusion is the most
important part of your laboratory notebook; it contains the key
findings of your experiment. Each experiment should contain a
conclusion, which is a specific statement about the important results
you obtained. Be careful about sweeping generalizations that are not
warranted by the experiment. Before writing a conclusion, it is useful
to review the purpose of the experiment. A good conclusion “answers”
the purpose of the experiment. For example, if the purpose of the
experiment was to determine the frequency response of a filter, the
conclusion should describe the frequency response or contain a
reference to an illustration of the response. In addition, the
conclusion should contain an explanation of difficulties, unusual
results, revisions, or any suggestions you may have for improving the
circuit.
Suggested Format
From the foregoing discussion, the following format is suggested. This
format may be modified as circumstances dictate.
1. Title and date.
2. Purpose: Give a statement of what you intend to determine as a
result of the investigation.
3. Equipment and materials: Include equipment
model and serial numbers, which can allow retracing if a defective or
uncalibrated piece of equipment was used.
4. Procedure: Include a description of what you did and what
measurements you made. A reference to the schematic drawing should be
included.
5. Data: Tabulate raw (unprocessed) data; data may be presented in
graph form.
6. Sample calculations: If you have a number of calculations, give a
sample calculation that shows the formulas you applied to the raw data
to transform it to processed data. This section may be omitted if
calculations are clear from the procedure or are discussed in the
results.
7. Results and conclusion: This section is the place to discuss your
results, including experimental errors. This section should contain key
information about the results and your interpretation of the
significance of these results.
Each page of the laboratory notebook should be signed and dated, as
previously discussed.
The Technical Report
Effective Writing
The purpose of technical reports is to communicate technical
information in a way that is easy for the reader to understand.
Effective writing requires that you know your reader’s background. You
must be able to put yourself in the reader’s place and anticipate what
information you must convey to have the reader understand what you are
trying to say. When you are writing experimental results for a person
working in your field, such as an engineer, your writing style may
contain words or ideas that are unfamiliar to a layperson. If your
report is intended for persons outside your field, you will need to
provide background information.
Words and Sentences
You will need to either choose words that have clear meaning to a
general audience or define every term that does not have a
well-established meaning. Keep sentences short and to the point. Short
sentences are easiest for the reader to comprehend. Avoid stringing
together a series of adjectives or modifiers. For example, the figure
caption below contains a jibberish string of modifiers:
Operational amplifier constant current source schematic
By changing the order and adding natural connectors such as of, using,
and an, the meaning can be clarified:
Schematic of a constant current source using an operational amplifier
Paragraphs
Paragraphs must contain a unit of thought. Excessively long paragraphs
suffer from the same weakness that afflicts overly long sentences. The
reader is asked to digest too much material at once, causing
comprehension to diminish. Paragraphs should organize your thoughts in
a logical format. Look for natural breaks in your ideas. Each paragraph
should have one central idea and contribute to the development of the
entire report.
Good organization is the key to a well-written report. Outlining in
advance will help organize your ideas. The use of headings and
subheadings for paragraphs or sections can help steer the reader
through the report. Subheadings also prepare the reader for what is
ahead and make the report easier to understand.
Figures and Tables
Figures and tables are effective ways to present information. Figures
should be kept simple and to the point. Often a graph can make clear
the relationship between data. Comparisons of different data drawn on
the same graph make the results more obvious to the reader. Figures
should be labeled with a figure number and a brief title. Don’t forget
to label both axes of graphs.
Data tables are useful for presenting data. Usually, data that are
presented in a graph or figure should not also be included in a data
table. Data tables should be labeled with a table number and short
title. The data table should contain enough information to make its
meaning clear: The reader should not have to refer to the text. If the
purpose of the table is to compare information, then form the data in
columns rather than rows. Column information is easier for people to
compare. Table footnotes are a useful method of clarifying some point
about the data. Footnotes should appear at the bottom of the table with
a key to where the footnote applies. Data should appear throughout your
report in consistent units of measurement. Most sciences use the metric
system; however, the English system is still sometimes used. The metric
system uses derived units, which are cgs (centimeter-gramsecond) or mks
(meter-kilogram-second). It is best to use consistent metric units
throughout your report or to include a conversion chart.
Reporting numbers using powers of 10 can be a sticky point with
reference to tables. Table 1-1 shows four methods of abbreviating
numbers in tabular form. The first column is unambiguous as the number
is presented in conventional form. This requires more space than if we
present the information in scientific notation. In column 2, the same
data are shown with a metric prefix used for the unit. In column 3, the
power of 10 is shown. Each of the first three columns shows the
measurement unit and is not subject to misinterpretation. Column 4, on
the other hand, is wrong. In this case the author is trying to tell us
what operation was performed on the numbers to obtain the values in the
column. This is incorrect because the column heading should contain the
unit of measurement for the numbers in the column.
Suggested Format
1. Title: A good title must convey the substance of your report by
using key words that provide the reader with enough information to
decide whether the report should be investigated further.
2. Contents: Key headings throughout the report are listed with page
numbers.
3. Abstract: The abstract is a brief summary of the work, with
principal facts and results stated in concentrated form. It is a key
factor for a reader to determine if he or she should read further.
4. Introduction: The introduction orients your reader to your report.
It should briefly state what you did and give the reader a sense of the
purpose of the report. It may tell the reader what to expect and
briefly describe the report’s organization.
5. Body of the report: The report can be made clearer to the reader if
you use headings and subheadings in your report. The headings and
subheadings can be generated from the outline of your report. Figures
and tables should be labeled and referenced from the body of the report.
6. Conclusion: The conclusion summarizes important points or results.
It may refer to figures or tables previously discussed in the body of
the report to add emphasis to significant points. In some cases, the
primary reasons for the report are contained within the body and a
conclusion is deemed to be unnecessary.
7. References: References are cited to enable the reader to find
information used in developing your report or work that supports your
report. The reference should include all authors’ names in the order
shown in the original document. Use quotation marks around portions of
a complete document such as a journal article or a chapter of a book.
Books, journals, or other complete documents should be underlined.
Finally, list the publisher, city, date, and page numbers.