ENGR 43
Lab Activity
Student Guide
Lab 3–Basic Use of the Oscilloscope and Function Generator
Student Name: ___________________________________________________
S3. Replicate a measured pulsating DC
waveform with a function generator
Overview
S4. Compile data into a test report.
In this lab activity, you will use the
oscilloscope to measure the waveforms at
the BOE opto-sensor input and the motor
drive output. You will replicate the motor
drive output with the function generator, and
use the oscilloscope dual-trace mode to
compare the motor output with the function
generator.
A1. Recognize the significance of the
oscilloscope as a primary tool for the
technician.
Time Needed
Lab Performance:
It should take students approximately 3.0
hours to work through the entire lab.
Before Starting This Activity
Review the following online learning
modules on the Wisc-Online website
(www.wisc-online.com):
 Oscilloscope Frequency Measurements
 Oscilloscope AC Voltage Measurements
 Oscilloscope DC Voltage Measurements
 Oscilloscope Phase Shift Measurements
Links to these learning modules are on the
GoogleDocs listing
(http://tinyurl.com/engr43-lablinks).
Lab Deliverables:
It should take students approximately 1.0
hours of homework time to create the lab
report summary.
Equipment & Supplies
Item
BOE-bot robot trainer
AA alkaline cells (batteries) –
installed in BOE-bot
1x/10x scope probes
BNC-to-clip test cable
AA alkaline cells (batteries) –
installed in BOE-bot
Learning Outcomes For Activity
Relevant knowledge (K), skill (S), or
attitude (A) student learning outcomes
4
2
1
4
Special Safety Requirements
K1. Define peak-to-peak voltage, period,
and frequency for AC waveforms

K2. Define period, pulse width, and duty
cycle for repetitive DC pulses
K3. Describe the function of the vertical,
horizontal, and triggering sections of
an oscilloscope
The BOE-bot wheels can present a pinch
hazard when moving. Keep fingers and
loose parts away from the wheels.
Lab Preparation
1. The BOE-bot must have the program
follow-line.bs2 loaded on the BASIC
Stamp microcontroller. The instructor
will confirm that you have the correct
software loaded.
S1. Measure peak-to-peak voltages, period,
and frequency of AC waveforms
S2. Measure period, pulse width, and duty
cycle of pulsating DC waveforms
Lab 3 – O-scope and Function Gen
ENGR 43
Quantity
1
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© 2012
ENGR 43
Lab Activity
Student Guide
Task #2 – Opto-Sensor Inputs
2. The BOE-bot must have the optical
sensor course tracking board installed.
Verify that the board is mounted
securely on the front of the robot.
The “eyes” of the robot are light-sensitive
resistors. In this task we will measure the
sensitivity of the resistors in the same
manner as the microcontroller.
1. Place the Boe-Bot power switch in
position 1. This powers the electronics
on the board, but does not supply power
to the motors.
2. Connect the 1x/10x scope probe to the
Channel 1 input on the oscilloscope (Oscope). Set the 1x/10x switch to 1x. Set
the o-scope channel 1 probe multiplier to
1x. (The probe multiplier and the oscope setting should always match.)
Connect the black (ground) lead of the
test probe to the same row as the black
lead (Vss) from the opto-sensor board,
and the red lead to the proto board in the
same row that the red lead (left sensor)
from the opto-sensor board. You may
use short 22 ga solid jumper wires to
make the connections from the test cable
to the proto board.
Introduction
You are the technician responsible for
troubleshooting opto-sensor and motor drive
problems on the BOE-bot for the “ESYS
500 Robo-Race.” In order to efficiently
isolate problems on a malfunctioning unit,
you need to measure a functioning unit so
you will have a baseline for comparison.
Task #1 – Tek MSO2014
Oscilloscope Introduction
Download the PDF file for the Tek Demo 2
Manual, or use one of the printed copies in
the lab.
1. We are substituting the Fluke function
generators for the demo board in this
task. Connect the BNC-to-clip test lead
to the output connector of the function
generator. Do not insert the connector
at an angle or force the connector!
2. Turn on the Fluke function generator and
press the front panel “Output Enable”
button. Locate the front panel button to
change the output waveform to a square
wave. Use the front panel keypad to set
the frequency to 1.25 MHz and the
amplitude (on the VHiZ setting) to 4
Vpp.
3. Complete the demo activites on pages 2
through 20 in the Tek Demo 2 Manual.
Note that in the PDF file, there are six
pages of introduction before the
numbered pages, so add 6 to the above
page numbers.
Lab 3 – O-scope and Function Gen
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ENGR 43
Lab Activity
Student Guide
3. Push the AUTOSET button on the oscope. A waveform should appear on the
scope display. Check the scope settings.
Adjust from the default settings if
necessary:
Channel 1 coupling: DC
Channel 1 Vertical Position: 0-volt
reference (arrow) at center of screen
Channel 1 V/div: 2
Time base s/div: 10 ms
4. Adjust the V/div, s/div, ch 1 vertical
position, and horizontal position. Note
the effect on the waveform display. Note
that this is only changing how you are
looking at the waveform. The waveform
itself remains the unchanged.
6. Adjust all of the above controls to
produce a waveform display that shows
a minimum of two complete periods of
the waveform, with the zero-volt
reference three divisions below the
centerline, and the vertical height at
maximum without exceeding the top of
the display.
7. Sketch the waveform. Identify the shape,
period, and amplitude of the waveform.
Use the horizontal and vertical cursors to
assist in your measurements.
Changing V/div:___________________
________________________________
Changing s/div: ___________________
________________________________
8. The BOE-bot software monitors this
signal and measures the time for the
falling edge signal to drop (the “decay
time”) to 1.4V. What is the time from
the start of the drop to the 1.4V level?
Set the horizontal scale to a faster s/div
to expand your view of the falling edge
and use the cursor function on the scope
to improve the accuracy of this
measurement.
Decay time (light) = ________
Changing vertical position: __________
________________________________
Changing horizontal position: ________
________________________________
5. Examine the change in the waveform
when the channel 1 coupling is switched
to AC and to GND. Note the changes:
9. Cover the left photoresistor with your
finger. How did the waveform change?
DC to AC coupling: _____________
______________________________
_____________________________
______________________________
What is the decay time?
DC coupling to GND: ___________
_____________________________
Lab 3 – O-scope and Function Gen
ENGR 43
Decay time (dark) = ________
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© 2012
ENGR 43
Lab Activity
Student Guide
10. Move the scope probe to the proto board
in the same row that the green lead (right
sensor) from the opto-sensor board. You
may use short 22 ga solid jumper wires
to make the connections from the test
cable to the proto board. Repeat the
measurements for the left photosensor.
Are the results similar for the light and
dark measurements? How are they
different (or, are they)?
Period: number of divisions______ X
s/div __________ = _________
Period: cursor measurement __________
Pulse width: number of divisions ____X
s/div __________ = _________
Pulse width: cursor measurement
_______________________________
____________
Sketch the waveform in the P12
graticule below.
P12
_______________________________
_______________________________
_______________________________
Task #3 – Motor Drive Outputs
1. If the “eyes” of the robot are lightsensitive resistors, then the “legs” are the
motors. Connect channel 1 test probe to
the leg of the resistor in the P12 socket.
Be careful not to short the two resistor
leads together. Leave the probe ground
clip on the BOE-bot Vss line. Press the
AUTOSET button. Adjust the o-scope
controls to display two complete periods
of the waveform, DC coupled, with the
0-volt reference on the center of the
screen, and a height of two to four
divisions.
2. Measure the period and the width of the
positive pulse of the waveform by
counting horizontal divisions and
multiplying by the s/div scale. Use the
cursors to check your measurement.
After you complete the period
measurement, change the s/div to a
shorter time to measure the pulse width.
Lab 3 – O-scope and Function Gen
ENGR 43
V/div = _____ s/div = _____
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© 2012
ENGR 43
Lab Activity
Student Guide
3. Connect a second 1x/10x scope probe to
the Channel 2 input on the o-scope. Set
the 1x/10x switch to 1x. Set the o-scope
channel 1 probe multiplier to 1x.
Connect the probe to the other side of
the same resistor, the side that connects
to the LED. Turn on the channel 2
display. Adjust the V/div to the same
setting as channel 1. Sketch the
waveform in the LED graticule below.
What is similar, and what is different
about the two waveforms?
4. While monitoring the pulse width, cover
the left photoresistor with your finger,
and then move your finger to the right
photoresistor. How does this affect the
pulse width?
____________________________
______________________________
5. Put the power switch to position 2 to
turn on the servo motors. The
specifications for the servo motors state
that the motors should be still when the
pulse width is 1.5 ms, turn one direction
when the pulse width narrows, and turn
the opposite direction when the pulse
width increases. Which direction,
clockwise (CW) or counter-clockwise
(CCW), does the motor turn when the
pulse width narrows? (hint: you may
unplug the motor connector from P13 to
determine which motor is connected to
P12).
_____________________________
____________________________
____________________________
____________________________
______________________________
______________________________
LED
____________________________
____________________________
V/div = _____ s/div = _______
_____________________________
Deliverable(s)
Save your completed Lab 3 Worksheet and
your Performance Report (at the end of this
document) in your Lab Activity Binder.
Lab 3 – O-scope and Function Gen
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© 2012
ESYS 50
Lab Activity
Student Guide
Lab 3 Basic Use of the Oscilloscope and Function Generator
Performance Report
Student Name: ___________________________________________________
Note: Print and turn in the performance report pages along with the lab activity procedure pages.
Scope Measurements
What was the effect of switching between AC and DC coupling? How did the display change?
How did your calculated voltage and time measurements (number of divisions multiplied by
V/div and s/div) compare with the cursor measurements? Which do you think is more accurate,
and why?
When examining the waveforms at P12 and
at the LED, P12 is the source voltage
supplied by the STAMP microcontroller,
and the voltage drops are across the resistor
and the LED. Since we measured the source
voltage and the voltage across the LED, we
can determine the voltage across the resistor
by subtracting the voltage of the LED from
the source voltage at each horizontal point to
create the voltage waveform across the
resistor. Sketch the voltage across the
resistor by using the above method.
Lab 3 – O-scope and Function Gen
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© 2012