Transcript Chapter 5

Chapter 5
Engineering Tools for
Electrical and Computer
Engineers
Introduction
 Many tools are available for electrical
and computer engineers in their
everyday work.
 These tools include meters used to
measure voltages, currents, field
strengths; oscilloscopes used to view
waveforms, and a variety of computer
based software and hardware.
General Ideas and Safety
Considerations
 When
working
with
electrical
equipment safety should have the
uppermost priority.
 Mistakes or carelessness pose danger
to the user and others, and may
damage
expensive
equipment
delaying the completion of the project
or experiment.
General Ideas and Safety
Considerations
 When dealing with new equipment you
should start by studying the operation
manual.
 This first step ensures that the type of
measurement being attempted is possible
with that instrument
 You should determine the maximum levels
of voltages and currents that can be applied
to the instrument and, that the values
expected in the experiment do not exceed
these maximum values.
General Ideas and Safety
Considerations
 When connecting a circuit it is safest to
ensure that the power source is connected
last and disconnected first.
 When dealing with DC circuits it is standard
to use red wires for positive voltages and
black wires for negative voltages.
 Never assume that a circuit is dead just
because the switches are off, mechanical
switches may be damaged causing serious
injury to the user or even death.
General Ideas and Safety
Considerations
 Use a voltage meter every time to make
sure that the voltage is what you expect it
to be.
 The application of the measurement
instrument introduces error to the quantity
being measured.
 It is the responsibility of the person taking
the
measurement
to
know
the
characteristics and limitations of the
measuring instrument to be able to predict
the amount of error it introduces to the
measured quantity.
Meters
 Meters used in measuring electrical
quantities include analog and digital
types.
 Analog meters are read by noting the
position of a needle on a scale.
 Newer meters are digital, these have
numerical or digital readouts.
 The most common type of meters is
VOM
meter,
this
reads
voltage,
resistance, and current.
Meters
 The quantity being measured and the range
are adjusted by knobs on the face of the
meter.
 It is important to choose the proper range
for the quantity being measured, to avoid
burning the meter it is best to start with
the maximum range and go down to the
proper range.
 Cheaper instruments are expected to
introduce larger errors.
Oscilloscopes
 An oscilloscope is used to observe
time-varying voltages or currents on
a screen.
 Computers can also be used as virtual
oscilloscopes when equipped with the
proper hardware and software.
 There are many controls on an
oscilloscope, so it takes practice
before you master it.
Computers
 Computers can be used to control electrical
test equipment such as meters and
oscilloscopes, they can also be used to
record measurement parameters and test
data.
 Computers can be used to coordinate the
activities of several test equipment tools
through a local network, this would require
writing a simple program to interface the
computer and the test equipment.
 Computers can be used as virtual
instruments.
Application Software
 Software tools are used to aid in
designing new devices, analyzing the
operation of existing devices, and to
help with tasks such as data analysis.
 Following are some types of these
tools.
Problem Solving Software
 These help in solving complicated problems
with matrices, complicated integrals, and
large systems of simultaneous linear
equations.
 These include packages such as: MATLAB,
MATHCAD, Mathematica, MAPLE.
 Advanced software packages can do image
processing, signal processing, control
system design.
Circuit Simulation
 Circuit simulators allow an engineer to
enter all the circuit components and
interconnections to a computer program.
 The program collects data about how the
circuit operates and all the output and
parameter values involved, and predicts the
behavior of the circuit when a certain
parameter is varied, it also provides plots
for the outputs.
 Examples of these programs are Pspice,
EWB.
Data Acquisition and Control
 When testing the performance of a circuit or
system. The parameters of the circuit need to
be set and meters connected, the data is then
recorded and the parameters are changed and
new data recorded, finally graphs of this data
are produced to help understand the results.
Doing this manually is tedious and takes a long
time.
 Data acquisition software such as LABVIEW, the
test equipment is connected to a computer, the
program then does all the tasks describe above
in a much shorter time.
Spreadsheets
 Spreadsheets
can
import
data
generated
in
experiments
and
perform calculations on that data.
 The data can be exported from
spreadsheets to other applications to
plot them or do further processing.
 Excel, Lotus123 are examples of
spreadsheet softwares.
Databases
 Database software such as Access,
are used to store large amounts of
information, label it according to one
of its attributes, and then retrieve the
information according to these labels.
 They also allow for graphing of the
data and aid in the preparation of
reports.
Graphing
 Plots of data can be very helpful to an
engineer in understanding and predicting
the behavior of their devices.
 MATLAB
has
powerful
graphing
capabilities.
 Some plotting software allow for graphing
special types of plots such as Smith
charts used in electromagnetics to plot
the behavior of the transmission line.
Word Processing
 Engineers
are
often
required
to
communicate their ideas and their work in
the form of written reports.
 Word processors such as Word or
WordPerfect allow them to easily compose
and edit documents, and produce high
quality
printout,
graphs
and
tables
generated by other software packages can
be easily imported and pasted into the
word processor.
Presentation Preparation
 Engineers are often required to make oral
presentations of their work.
 Software such as Powerpoint help in
producing high quality, visually exciting
presentations.
 It is also possible to import graphs, pictures
in other software packages to combine
them in the presentation.
 These programs can also run projectors
that display the presentations.
Programming languages
 An engineer must master one or
more of the available high-level
languages to be able to write a
program for performing the different
tasks encountered in his line of work.