# how to use Oscilloscope by AhmedFarahat1

VIEWS: 4 PAGES: 48

• pg 1
```									              Uploaded by www.farahat-
library.com
   Visit us @ http://www.farahat-library.com/blog/
USE OF THE OSCILLOSCOPE
Science Learning Center
University of Michigan – Dearborn

Modified from a presentation written by David Matzke by: Donald
Wisniewski, Dawn Wisniewski, Huzefa Mamoola and Angela Nolte

Under the direction of: Dr. Ruth Dusenbery and Dr. Paul Zitzewitz

With funds from the Office of the Provost, UM-D, and NSF CCLI
grant DUE#9952827 to RD and PZ.
OBJECTIVES
In this module you will learn how use an
oscilloscope to:

 measure direct current (D.C.) voltage and

 measure alternating current (A.C.) voltage.
Equipment
Make sure that you
have the following
before you begin:

   an oscilloscope
   a function generator
   a six volt battery and
   two cables
CRT Screen                Control Panel

Input Channel Selector
Oscilloscope Screen

   Notice that the screen
has ruled divisions
both horizontally and
vertically.
   The major divisions
are marked off in
centimeters, the
middle lines also
have minor divisions
every 0.2 of a
centimeter.
Input Channel Selector
   This area is broken into two parts: the left half for
channel A and the right half for channel B.
   In the center of this section lies the mode switch
that determines which channel will serve as an
input to the scope:A, B or Dual.
   For this module we will only be concerned with
channel A.
Channel A                     Channel B
Control Panel
   The section to the
right of the screen
contains the controls
the triggering and
sweep time of the
waveform.
   This section is
generally used when
measuring the period
of A.C. waveforms.
Turning the Oscilloscope ON
   Now turn the power
switch located to the
right of the screen to the
ON position.

   Make sure the triggering
level knob is pulled out
for AUTO operation.

   A line or dot should
appear on the screen.

   If not, check that the
position switches and
intensity dial point up.
Set Mode Switch
   The oscilloscope is
capable of measuring
voltages from two
different sources.

   The mode switch is used
to alternate between
sources.

   For the purposes of this
module, set the mode
switch to Channel A.
Connect Cable
   A cable should be
connected to the input
of Channel A.

   The other end of the
alligator clips. These
should not be
connected to anything
at this point (if they
are, then disconnect
them).
Sweep Time per centimeter Switch

   Look at the “sweep
time per centimeter”
knob.

   Turn the outer dial of
the sweep time per
centimeter to 2
milliseconds (ms).
Horizontal Position
   The horizontal line
should be centered
using the horizontal
and vertical position
knobs.

   Make sure the
horizontal position
knob is pushed in.
Intensity and Focus Dials

   The intensity dial
controls the
brightness of the line.

   The focus dial
controls the
sharpness of the line.
Summary Measuring DC Voltage
To get started you should follow these steps:
 Set mode to channel A.

 Connect cable to input. Leads should be free.

 Turn power ON and wait for dot or line to appear.

 Pull Triggering level knob out.

 Adjust intensity and focus as needed.

 Set sweep time /sec knob till the line on the screen
 Adjust horizontal and vertical position knob to
make sure that the line is fully visible.
Measuring a Direct Current Voltage

   Switch the A.C.-GND-D.C.
switch to the D.C. position.

   Set the volts/cm dial on 1.

   Turn the beige dial
clockwise all the way to
put the volts/cm dial in the
“calibrated” position.
Volts/cm Dial
   The volts/cm dial tells
you the number of
volts to be
represented by each
centimeter vertically
on the screen.

   Here the outer dial is
set to one, so each
centimeter equals
one volt.
Checking Oscilloscope Calibration
Use the vertical
position dial to move
the baseline near the
bottom of the screen.
Connect Cables
   Now take the cable
connected to the
input and connect the
negative terminal of
the 6 volt battery.

   Take the red lead and
touch it momentarily
to the positive post of
the battery.
   The line on the
oscilloscope should
deflect upwards when the
positive connection is

   The amount that the line
deflects vertically tells us
the voltage of the battery.

   Fasten the red lead to the
positive post of the battery

   The line should have
(corresponding to 6 v).

   Set the baseline to the
center position.

   Turn the volts/cm dial to 2.

   Fasten the red lead to the
positive terminal again.

   The line on the
oscilloscope should now
each cm represents 2 v.
   Notice that the volts/cm dial does not change
the voltage.

   It is a sensitivity dial that allows us to measure a
wide range of voltages by telling us how much
voltage is represented by each centimeter along
the Y-axis.

   Disconnect the battery from the leads on the
input cables.
Measuring a Time Varying (A.C.) Voltage
   Now look at the Function Generator. This
device produces a voltage that changes over
time.

   For purposes of this module, not all the features
of the function generator will be discussed.
Initial Setup
   Before any work is to
be done on the
function generator, be
sure that all the dials
are turned completely
clockwise and all
buttons are in their
outward position.
   There should also be a
to the Main Output.
Amplitude Dial

   This dial is used to adjust the peak to peak voltage of
the AC waveform from 0 to 25.

   Set the amplitude to max by turning the dial completely
clockwise.
ATT Button
   This is the attenuation button. It is used to set the
amplitude of the signal to a significantly smaller
range.

   This button should be in the OUT position unless
otherwise directed.
Function Buttons

   These button are located
at the upper right corner
of the generator.
Selecting a button sets
the type of voltage
change over time as a
square, triangular or sine
wave.
   Press the button for the
sine wave.
Frequency Dial and Range Buttons

   The frequency dial
and range buttons are
used in conjunction
when setting the
frequency of the
waveform.
   Pressing a range
button will multiply
the value of the
frequency dial by that
of the range button.
Frequency Dial and Range Buttons
   Set the FREQUENCY dial to 1.0 and press the range
button 10.
   The resulting frequency is 10 cycles/sec.
Frequency and Frequency Multiplier
   Now set the FREQUENCY dial to 0.8 and the
FREQUENCY MULTIPLIER to 1k.
   The resulting frequency is 800 cycles/sec.
Connecting the Function Generator
to the Oscilloscope
   Connect the
alligator clip of
from the function
generator to the
alligator clip of
from the
oscilloscope.

   Do the same with
Measuring a Time Varying (A.C.) Voltage
   Set the volts/cm dial to 5,
making sure the inner
beige dial is turned fully
clockwise.
   Remember each cm in the
Y-axis represents a certain
number of volts, in this
case, 5/cm.
   Change the AC-GND-DC
switch to A.C. and raise
vertical position switch.
Setting the Sweep Time
   The sweep time/cm knob
contains two dials.
   The inner beige dial is a fine
fully clockwise.
   The numbers corresponding
to the outer dial represent the
amount of time per cm in the
X-direction.
   Set this to 2 ms.
   Now use the triggering
level dial and the sync
and source switches
necessary.

   Flip the source switch
to INT in order to
ensure that the sine
wave starts from the
same spot every time
the electron beam
sweeps across the
screen.
Measuring Voltage
   Position the wave so
that the bottom of a
wave is lined up with
one of the cm
markings.

   Measure the number of
cm’s from the bottom
of the wave to the top.

   Multiply the number of
cm’s by the volts/cm
sensitivity to get the
maximum peak
voltage. This should
be about 20-25 volts.     4.3 cm x 5 V/cm = 21.5 V
Measuring Frequency
   Position the sine wave
so that the beginning of
the wave lines up with
the cm position along
the x-axis.
   Count the number of
cm’s along the x-axis of
one cycle and multiply
by the sweep time per
cm.
   You should get 10 ms
or 0.010 sec. The
inverse of this is the
frequency, which is 100
cycles/second.
5 cm x 2 ms/cm = 10 ms
Changing the Oscilloscope Settings

   Remember that the
function generator is
producing the voltage
and frequency. The
oscilloscope is merely
measuring the output.

   Change the volts/cm
dial to 10 and the
sweep time/cm dial to
5 ms/cm.
Changing the Oscilloscope Settings.
   Watch the wave form
change as you change
the volts/cm dial to 10
and the sweep time/cm
dial to 5 ms/cm.

level knob if necessary
to get a stable image.

   You should still be
cycles/sec.
Using the 5X Feature on Horizontal Knob
   Pull the horizontal
knob OUT.

   Notice that it spreads out
wave magnifying it 5
times. We can use this
feature to zero in on part
of the wave.

   Push it back in before
continuing.
Changing Function Generator Settings
   Now change the AMPLITUDE dial on the
function generator.

   Notice that the reading on the
oscilloscope changes.

   Dial in a different frequency.

   Remember that this changes the time for
one wave on the oscilloscope.
Attenuation
   The attenuation button is used to output small
voltages.
   Press the ATT button on the function generator to the
IN position and observe the voltage on the
oscilloscope.
   Adjust the controls on the oscilloscope if needed to
properly observe the signal.
Summary Measuring AC Voltage
   Turn on the function generator by pressing in the power
button.
   Turn all dials completely clockwise and ensure all
buttons are in the outward position.
   Press the function button of the desired wave function,
i.e., triangle, square, or sine wave.
   Set the frequency dial and the press the range button of
the function generator to achieve the desired frequency.
   Connect the leads of the function generator’s output to
Summary Measuring AC Voltage
   Flip the AC-GND-DC switch to AC on the oscilloscope.
   Set the VOLTS/CM dial to proper sensitivity; remember to
twist the inner dial clockwise as far as possible.
   Set the sweep TIME/CM dial to proper sensitivity. Twist
the inner dial clockwise as far as it will go.
   Make sure the picture is centered on the screen using the
vertical and horizontal position dials.
   Flip the source switch to internal.
   If necessary, adjust the triggering level knob until you get
a steady picture. The triggering level knob should be
pulled out.
   Adjust the intensity and focus to get a good sharp image.
Practice Problem #1

   Set frequency to 100 Hz.
   Set attenuation to 10.
   Find the peak to peak voltage and
   Find the time period for one cycle.

   Peak to peak voltage = 7 volts
   The time or period = 1 ms.
Practice Problem #2

   Set frequency to 50 Hz.
   Set attenuation to 30.
   Find the peak to peak voltage and
   Find the time or period for one cycle.