Florida Institute of Technology © 2020 by J. Gering Experiment 6 The Oscilloscope Introduction . This experiment consists of several procedures designed to familiarize you with the operations of a dual trace oscilloscope. The key measurements obtained from an oscilloscope’s CRT screen are voltage (from the peak-to-trough amplitude) and frequency. A Pre-Lab exercise or quiz may be assigned. It will provide a diagram and description of the many knobs, buttons and banana jacks on a typical oscilloscope. The last part of the procedure demonstrates a few additional features of the oscilloscope, and alternating voltages. Note: This week’s activities are focused on learning how to use a piece of equipment rather than learning physics and testing a physical relationship. Therefore, the lab report for this experiment can be shorter than usual. An over-all discussion and a conclusion for this experiment’s report is not needed. Concept . An oscilloscope is a visual A.C. voltmeter. “Scopes” produce a graph of voltage (on the y-axis) versus time (on the x-axis) on the screen of a cathode ray tube. This standard piece of electrical test equipment is found in many laboratories. The amplitude and period of repetition of the voltage signal are read directly from the CRT screen. An oscilloscope is composed of several circuit building blocks. Individually, each circuit is complex, but each block can be viewed as a whole (Fig. 1). The heart of an oscilloscope is the cathode ray tube (CRT) where a beam of electrons scans across a phosphorescent screen. This is how the oscilloscope draws a two-dimensional graph (called a trace). Refer to your textbook for information about a CRT. � Figure 1. Block Diagram of a Basic Oscilloscope First, the input is amplified so that it is large enough to drive the vertical deflection plates of the CRT. The sweep circuit produces a “sawtooth” or ramp voltage. This voltage is applied to the CRT's horizontal deflection plates so while it increases, the beam of electrons moves from left to right across the CRT screen at a constant rate. When the sawtooth voltage drops quickly to zero (the down stroke of the sawtooth) the beam moves back to the left hand side of the screen. The trigger circuit synchronizes the input signal with the sweep circuit. In other words, there is a prescribed voltage, which causes the sweep circuit to begin moving the beam across the screen. Sometimes the input signal is noisy and cannot begin the sweep at the correct instant. Therefore, Cathode Ray Tubevertical amplifier trigger circuit sweep circuit input horizontal amplifier 6 - �1 Florida Institute of Technology © 2020 by J. G ...

1. Florida Institute of Technology © 2020 by J. Gering
Experiment 6
The Oscilloscope
Introduction
.
This experiment consists of several procedures designed to
familiarize you with the operations of
a dual trace oscilloscope. The key measurements obtained from
an oscilloscope’s CRT screen
are voltage (from the peak-to-trough amplitude) and frequency.
A Pre-Lab exercise or quiz may
be assigned. It will provide a diagram and description of the
many knobs, buttons and banana
jacks on a typical oscilloscope. The last part of the procedure
demonstrates a few additional
features of the oscilloscope, and alternating voltages.
Note: This week’s activities are focused on learning how to use
a piece of equipment rather than
learning physics and testing a physical relationship. Therefore,
the lab report for this experiment
can be shorter than usual. An over-all discussion and a
conclusion for this experiment’s report is
not needed.
Concept
.
An oscilloscope is a visual A.C. voltmeter. “Scopes” produce a

2. graph of voltage (on the y-axis)
versus time (on the x-axis) on the screen of a cathode ray tube.
This standard piece of electrical
test equipment is found in many laboratories. The amplitude
and period of repetition of the
voltage signal are read directly from the CRT screen.
An oscilloscope is composed of several circuit building blocks.
Individually, each circuit is
complex, but each block can be viewed as a whole (Fig. 1). The
heart of an oscilloscope is the
cathode ray tube (CRT) where a beam of electrons scans across
a phosphorescent screen. This is
how the oscilloscope draws a two-dimensional graph (called a
trace). Refer to your textbook for
information about a CRT.
�
Figure 1. Block Diagram of a Basic Oscilloscope
First, the input is amplified so that it is large enough to drive
the vertical deflection plates of the
CRT. The sweep circuit produces a “sawtooth” or ramp voltage.
This voltage is applied to the
CRT's horizontal deflection plates so while it increases, the
beam of electrons moves from left to
right across the CRT screen at a constant rate. When the
sawtooth voltage drops quickly to zero
(the down stroke of the sawtooth) the beam moves back to the
left hand side of the screen.
The trigger circuit synchronizes the input signal with the sweep
circuit. In other words, there is a
prescribed voltage, which causes the sweep circuit to begin
moving the beam across the screen.
Sometimes the input signal is noisy and cannot begin the sweep

3. at the correct instant. Therefore,
Cathode Ray Tubevertical
amplifier
trigger
circuit
sweep
circuit
input
horizontal
amplifier
6 - �1
Florida Institute of Technology © 2020 by J. Gering
a control knob is used to manually adjust the amount of input
voltage necessary for the sweep
circuit to begin operation. This voltage is called the trigger
level. Also, a trigger control button
allows you to begin the sweep on either the rising or descending
portion of the input waveform.
This is called inverting the slope of the trace. Since the sweep
circuit moves the beam of
electrons across the screen at a constant rate, the trace usually
represents a display of voltage
versus time. Operationally, an oscilloscope trace is triggered
when the input signal becomes
stationary and does not travel across the screen.

4. Method
.
The BK Precision model 2120B Oscilloscope is a dual-trace,
triggered, 30 MHz oscilloscope.
Dual trace means this scope can display two different voltage
signals at the same time. 30 MHz
means that A.C. voltages with a frequency of up to 30 x 106
cycles / sec can be displayed.
AC voltages are supplied by a signal generator, which contains
a frequency control dial. The
frequency is the dial reading multiplied by the range number set
by push buttons on the
instrument. An additional dial is used to adjust the amplitude
of the output signal. It is
graduated in arbitrary units.
Often, an oscilloscope is used to measure a sinusoidal voltage
signal’s peak-to-peak voltage. See
Fig. 2. Ruled on every scope screen is an X/Y grid where each
major division (large square)
equals the setting on the volts per division (VOLTS / DIV)
knob.
To measure the peak-to-peak voltage, count the number of
divisions (large squares) spanned by
the signal in the Y direction and multiply by the setting of the
VOLT/DIV knob. To measure the
period, count the number of major divisions spanned by one
cycle of the wave along the time (X)
axis. Multiplying this number by the setting of the TIME / DIV
knob gives the period, T.
Usually you want to know the wave’s frequency. Recall that
frequency, f = 1 / T. The units of
frequency are reciprocal seconds, which are called Hertz (Hz) in

5. honor of the physicist Heinrich
Hertz who (among other things) discovered radio waves.
!
Figure 2. Voltage Versus Time Graph of a Sinusoidal
Alternating Voltage.
6 - �2
Florida Institute of Technology © 2020 by J. Gering
We have used two different signal generators in recent years.
One is the BK Precision 4011A
and more recently the Instek SFG-1013. The BK Precision
generator is simple and intuitive to
use. When you turn on the BK Precision unit, alternating
voltage is immediately available at the
OUTPUT coaxial terminal (jack). Push buttons change the
range of frequencies the unit delivers
and a rotary knob adjusts the frequency within that range. A
separate knob, labeled OUTPUT
LEVEL raises and lowers the peak voltage to 10 Volts. The
digital display of the frequency on
the BK Precision is approximate.
!
Figure 3. BK Precision 4011A Signal Generator
The Instek signal generators are more complicated to use
because they employ more digital
electronics to provide precise frequencies. They also deliver
higher frequencies. After pressing
the POWER button, one must also press the OUTPUT ON

6. button before alternating voltage is
available at the MAIN coaxial terminal. The digital display of
the frequency is much more
accurate on the Instek models. Also, these generators allow the
frequency to be set to an
impressive 0.1 Hz at all frequencies.
!
Figure 4. Instek SFG 1013 Signal Generator
There are two ways to set or adjust the frequency on the Instek
generators. One can simply use
the numeric buttons to type in a frequency, then press the blue
SHIFT button and then press
either Hertz, kilo-Hertz or mega-Hertz. For example one can
enter 1250, SHIFT, Hz or 1.25
SHIFT, kHz.
6 - �3
Florida Institute of Technology © 2020 by J. Gering
The other way to set or adjust the frequency on the Instek is to
use the rotary FREQUENCY
knob. The frequency knob on the BK Precision has a definite
range. One can only rotate the
knob so far clockwise and counter clockwise. In contrast, the
frequency knob on the Instek has
no limit in either direction. One can keep turning and turning
it. With some initial frequency on
the display, one can change it with the knob by pressing SHIFT
and then the blue arrow buttons
once or repeatedly. One of the display’s digits will begin to
blink and you can move that

7. blinking “cursor” to the digit you want to change. Then rotate
the knob. Once you start turning
the knob, the Instek will only allow adjustment of that digit.
Clearly, the frequency knob is best
suited for making fine adjustments to the frequency instead of
setting an initial frequency that is
very different from the default value after turning on the
generator.
Procedure
.
Part 1 Initial Set - Up, DC Volts and a Square Wave
Item Setting Item Setting
INTEN mid-range TIME/ DIV 1 ms
FOCUS mid-range VAR SWEEP calibrated
(clockwise)
POSITION (y axis) mid-range POSITION (horizontal)
mid-range
VOLT / DIV (outer) 0.5 V / DIV TRIG LEVEL mid-
range
(both) VOLT/DIV (inner) CAL’D TRIGGER COUPLING AUTO
CH 1 selector switch DC (in) TRIGGER SOURCE
CH 1
VERT MODE CH 1 HOLD OFF minimum setting
1) Before turning on the oscilloscope, set up its front panel as
above. Then, turn ON the
oscilloscope. Adjust the trace to a moderate level of brightness
with the INTEN knob.
2) Question: What will a DC voltage trace look like? Draw a
picture of your answer before
continuing. Turn the D.C. power supply’s voltage knob to
minimum and then turn ON the

8. supply. Connect its negative jack to the scope's ground jack.
Connect the power supply’s
positive jack to CH 1. Raise the supply’s voltage. Measure and
record that the power
supply's meter agrees with readings the scope’s readings.
3) Turn the DC power supply’s voltage to a minimum,
disconnect the wires to the supply and
turn it OFF. Connect the signal generator to the scope’s CH1
input. The signal generator
has coaxial cable jacks rather than banana plug jacks. The
center conductor carries the
signal, and the outer metal jacket is grounded. An adapter
allows a banana plug to connect
to the center (signal) terminal. Ground the signal generator by
connecting an alligator clip
to the outer conductor jacket of any of the generator’s
terminals.
4) Push the button on the signal generator to produce a sine,
square or triangle wave. Make
sure the coupling source is CH 1. Then use the scope’s TRIG
LEVEL knob (i.e. the
manual triggering control) to “freeze” the waveform.
6 - �4
Florida Institute of Technology © 2020 by J. Gering
5) Adjust the VOLTS / DIV knob and TIME / DIV knob for a
nice display. Center the
waveform on the screen both horizontally and vertically.
6) Measure the peak-to-peak voltage of your wave and its

9. frequency. Change the frequency
and amplitude controls on the signal generator, which may be
either knobs or buttons
depending on the model of the signal generator. Repeat these
measurements so each lab
partner can practice reading from the oscilloscope screen.
7) It is the DC setting on the switch labeled AC, GND, DC that
displays any constant voltage
in an alternating voltage signal. Set the CH1 toggle switch to
DC and turn the signal
generator’s OFFSET knob. Sketch two representative
waveforms on your data sheet and
include a zero Volt reference line.
8) Next, pull the horizontal POSITION knob out. Question:
What does this do to the trace?
After recording your answer, push the knob back in.
Part 2 Sinusoidal Voltages
1) Display two different sine waves on the scope. Measure their
peak-to-peak voltage and
frequency from the screen. Also record the frequency from the
signal generator and
compare both frequencies. Question: Which do you feel is the
more accurate? As you
change the signal generator’s amplitude and frequency control
knobs, adjust the scope’s
VOLTS/DIV and TIME/DIV knobs to keep several cycles on the
screen.
2) Report on the effects of varying the inner knobs on the VOLT
/ DIV knobs and TIME / DIV
controls when the VARIABLE knobs are not in the CAL'D
(calibrated) position.

10. 3) Display a sine wave and then call your instructor and
announce that you are ready to take
the dreaded “Scope Rating Test”. You will leave the table for a
few minutes while your
instructor scrambles your scope settings. Your must bring back
your original trace. After
doing this, you will be “scope rated” and your instructor will
sign your data sheet to this
effect. This test is given to each individual. Then, continue
with the rest of the experiment.
Part 3 Alternating Voltages Across Resistors in Series
1) Connect the signal generator to the oscilloscope. Without
anything else connected to the
signal generator, set the peak-to-peak amplitude of the signal
generator to 10 Volts.
Disconnect the scope. Build a series circuit containing the
signal generator, a 267 Ω
resistor and a 500 Ω resistor. Place the 500Ω resistor last in the
series before ground. Use
the scope to measure the voltage across the 500 Ω resistor.
Record this value. Next,
disconnect the Scope and switch the order of the two resistors
so the 267 Ω resistor is last
in the series. Again, use the Scope to measure the voltage
across the 267 Ω resistor.
Record this value. In your report, explain your values.
Question: Are the peak-to-peak
voltages you measured the same as what you would get if you
were using a D.C. power
supply in place of the signal generator and a digital voltmeter in
place of the Scope?
6 - �5

11. Florida Institute of Technology © 2020 by J. Gering
2) Questions: What was the phase relationship between all the
voltages measured in the two
previous procedures? What phase relationship exists between
the alternating current in
these circuits and the alternating voltages across the resistor s?
Part 4 Lissajous Figures and Beats
1) Note: Two signal generators are required for this part, so
work with another group.
Connect one signal generator to CH1 and the other to CH 2.
Display two very similar sine
waves. Press the X-Y button and switch the vertical mode to X-
Y. Make the frequency of
one signal generator an integer multiple of the frequency of the
other. Sketch and describe
typical patterns. See Appendix G for more information about
Lissajous Figures. Also, try
a Lissajous figure of a square wave and a triangle wave. Press
the X-Y button again to
reset the scope and disconnect the wires.
2) Connect two signal generators to one input jack. The scope
displays the arithmetic sum of
the two signals. Adjust the voltages and frequencies to obtain
the characteristic trace of
“beats”. Also ask your instructor to demonstrate acoustic beats.
A beat pattern is produced
by adding two waves of similar amplitude and slightly different
frequencies. Sketch a beat
pattern on your data sheet. Disconnect the wires when you are

12. finished and clean up your
station.
6 - �6
Experiment 06 Guide
The Oscilloscope
Adjustments for In-Person Students
Due to the shortened periods due to the pandemic, students can
omit procedure 3 of Part 2 and
all of Part 3. Students performing the experiment in the
laboratory perform all other parts of
the procedure.
In-person students should watch the video available on Canvas
at Pages > View All Pages. Be
aware that GSAs will minimize their introductory instruction
time so students have more
minutes to complete the procedure without rushing.
Instructions for At-A-Distance Students
All video clips have been saved in one (very large) MP4 video.
It is found in Canvas > Pages >
View All Pages. Note that some procedures in the manual refer
to a square but a sine wave was
used when the videos were recorded.
There is not much data to take in this experiment. You can
record some observations from
scenes in the video. The main tasks, after watching the video is

13. to complete the following
exercise to replace portions of the procedure. Be sure to answer
questions posed in Part 1 and
the first two procedures of Part 2 in the lab manual.
Part 5 - Replaces what remote students cannot perform in Parts
1 and 2
Since several procedures have been eliminated, include this new
part in your Data
Analysis. Run the following simulations. Include one screen
capture for each
simulation in your report.
1) This first simulator allows shows how different waves sound
and appear when the
alternating voltage creating the sound appears on an
oscilloscope-like screen.
http://www.physics-chemistry-interactive-flash-animation.com/
electricity_electromagnetism_interactive/
oscilloscope_description_tutorial_sounds_frequency.htm
2) This next simulator is a somewhat true to real life.
http://eleceng.dit.ie/dsp/elab/
3) Here is one that is actually an Excel spreadsheet.
http://www.engineers-
excel.com/Apps/Oscilloscope/Description.htm
Page � of �1 2
http://www.physics-chemistry-interactive-flash-

14. animation.com/electricity_electromagnetism_interactive/oscillo
scope_description_tutorial_sounds_frequency.htm
http://www.physics-chemistry-interactive-flash-
animation.com/electricity_electromagnetism_interactive/oscillo
scope_description_tutorial_sounds_frequency.htm
http://www.physics-chemistry-interactive-flash-
animation.com/electricity_electromagnetism_interactive/oscillo
scope_description_tutorial_sounds_frequency.htm
http://eleceng.dit.ie/dsp/elab/
http://www.engineers-
excel.com/Apps/Oscilloscope/Description.htm
Part 6 - Replaces Part 4 for Remote Students
1) Create an Excel spreadsheet that demonstrates sine-wave
superposition. In other
words, plot two sine functions with two different frequencies on
the same y-axis
with angle (in radians) on the x-axis. Add a third graph that is
the sum of first
two functions. Make a screen capture for your report and
include the cells
containing the equations. Display the equations used (see
procedure 4b below).
2) Duplicate the previous spreadsheet but only plot the sum of
the two sine functions.
Adjust the frequencies to produce beats. Make make screen
captures of two trials
and paste them into the Data section your report.
3) There are plenty of YouTube videos of Lissajous figures.
Watch these two videos.
https://www.youtube.com/watch?v=yfxbY0C1tXw

15. https://www.youtube.com/watch?v=uPbzhxYTioM
4) Create an Excel spreadsheet where you plot two different
sine (or cosine) functions,
one on the x-axis and one on the y-axis. Generate your own
Lissajous figure.
Remember that Excel expects angles to be in radians inside of
its trigonometric
functions.
a. Be sure to copy the equations you use into a cell just below
the column heading
but above the values to show the reader the equation.
b. Use the ‘trick’ of copying the cell’s equation and before
pasting it, insert a
blank space in the cell to prevent Excel from recognizing what
you are going to
paste as an equation. Then create a screen capture of your
Lissajous Figure
simulator (including the equations) and paste it into your report.
5) Lissajous figures that use triangle and square waves are very
cool. Here is a link
for the Excel formula necessary to produce a triangle wave.
Despite what is
written in the link, this formula does not use VBA, which is a
Microsoft Add-on
called Virtual Basic for Applications. Create an Excel
spreadsheet that creates a
Lissajous figure of two different triangle waves. Again, include
a screen capture in
your report.
https://www.quora.com/What-is-the-code-to-create-a-triangle-

16. waveform-in-Excel-using-
VBA-coding-given-the-frequency-of-10kHz-and-amplitude-of-
+-1
Page � of �2 2
https://www.youtube.com/watch?v=yfxbY0C1tXw
https://www.youtube.com/watch?v=uPbzhxYTioM
https://www.quora.com/What-is-the-code-to-create-a-triangle-
waveform-in-Excel-using-VBA-coding-given-the-frequency-of-
10kHz-and-amplitude-of-+-1
https://www.quora.com/What-is-the-code-to-create-a-triangle-
waveform-in-Excel-using-VBA-coding-given-the-frequency-of-
10kHz-and-amplitude-of-+-1