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DSO WBT Function Generator Exercise
12/08/09
Exercise: DSO Function Generator Exercise, Course 870293
Objective: Demonstrate the ability to capture, measure and
analyze electronic waveforms using the VAS 5051B DSO
Congratulations. You have successfully completed the DSO WBT
870294. The next step is to complete the DSO Function Generator
Exercise. The purpose of this exercise is to give you hands on
experience using the DSO based on what you learned previously.
In order to complete this exercise, you need a VAS 5051B and an
Elenco Electronics FG-500 1Mhz Function Generator. It is essential
that you purchase the FG-500 because you will not be able to answer
all of the questions in the final assessment unless you use the
FG-500 to complete this exercise.
The Elenco Electronics FG-500 1Mhz Function Generator can be
purchased on-line from one of the following sources (you may be
able to locate additional on-line sources as well):
http://techedu.com
http://www.tequipment.net
http://electronickits.com
On the home page for one of the above sites, type FG-500 in the
search field. There are two versions available, the FG-500 (factory
assembled version) and the FG-500K (kit version) We strongly
recommend that you purchase the FG-500 assembled version and not
the FG-500K kit version because it requires soldering and
assembly.
Once you have the 5051B and the FG-500, youre ready to perform
the exercise! Continue to the next page.
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DSO WBT Function Generator Exercise
12/08/09
Note: Do not try to rush through this
exercise! Remember that this is a learning process. Try to see
how accurately you can complete it, not how quickly. Take your time
and make sure that you understand each step before proceeding.
1. To start, configure the FG-500 as follows:
Make sure that the FG-500 has a good battery.
Turn the Coarse Frequency knob to 10.
Turn the Fine Adj. Frequency knob to the left
(counter-clockwise) until it stops.
Turn the Amplitude knob to the left (counter-clockwise) until it
stops.
Make sure that the On/Off switch is in the OFF position. It will
be turned on in a later step.
The Sine/Triangle switch will not be used in this exercise, so
it can remain in either position.
2. Start the VAS 5051B DSO by selecting:
Test Instruments
Go To
DSO
3. Connect the DSO to the Function Generator as follows:
Connect the DSO 1 red lead to the yellow banana jack labeled
Square Wave.
Connect the DSO 1 black lead to the black banana jack labeled
GND.
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DSO WBT Function Generator Exercise
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4. The first waveform is a relatively slow (low frequency)
signal. To properly view this waveform, Draw Mode must be used.
Select the Measuring Mode button.
Select the Draw Mode button.
Deselect the Measuring Mode button.
5. Turn the Function Generator ON. You should see a waveform
that is similar to the one at left. If the DSO screen does not look
like this:
Make sure that the battery in the FG-500 is OK.
Go back to the beginning of the exercise and read each step
carefully.
There are two things wrong with this waveform:
The waveform is displaying above the top of the screen (arrow).
A waveform should never display above or below the top or bottom of
the screen.
The individual pulses of the waveform are so compressed that
they are unreadable.
To remedy these problems, the DSO must be configured to display
the waveform properly, which you will do in the next steps.
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DSO WBT Function Generator Exercise
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6. To make the waveform fit the screen, the voltage division
must be changed:
Select Channel A.
Since the waveform needs to be smaller, the voltage division
must be made larger.
Select the voltage division arrow until the Channel A voltage
division displays 5 V/Div.
Deselect Channel A.
The waveform now fits the screen.
7. To make the induvidual pulses of the waveform visible, the
time division must be changed:
Since the pulses need to be wider, the time division must be
smaller.
Select the Time/Div. arrow until the time division displays 0.5
s/Div.
8. Now take a few moments to experiment with how the voltage and
time division buttons alter the appearance of the waveform. First
change the voltage division and then the time divsion up and down
while observing the changes to the waveform. When finished return
them to their previous settings:
5 V/Div.
0.5 s/Div.
Falling Flank
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DSO WBT Function Generator Exercise
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9. Notice that the height of the waveform only occupies about
25% of the screen. While this is perfectly acceptable, it may be
possible to make it taller. To do this, the zero point of the
waveform must be changed.
Select the Channel A button.
Move the slider down to the first division above the bottom of
the screen as shown at left.
Now press the voltage division arrow until the voltage division
for Channel A displays 2 V/Div.
Deselect the Channel A button.
10. The waveform is now looking good, but there still one
problem: The green Channel B waveform (DSO 2) is in the middle of
our waveform, which could make it hard to read. Two things can be
done to remedy this:
Move Channel B to the bottom of the screen (similar to how
Channel A was moved previously).
Turn Channel B off, which removes it entirely.
11. Lets do both.
Select Channel B.
To move Channel B, move the slider to the bottom of the screen
as shown at left. Now the Channel B waveform doesnt interfere with
the Channel A waveform.
To turn Channel B off entirely, select the Channel button, then
select OFF. This removes the waveform, and may be the best choice
for our next step, measuring pulse width.
Deselect the Channel button.
Deselect the Channel B button.
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DSO WBT Function Generator Exercise
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12. Before proceeding, lets review the names for the parts of a
waveform. Knowing the parts of a waveform will help you perform the
following steps.
Please refer to the Automotive Electrical Signals Glossary for
more information.
13. Now measure the amplitude of the high and low signal
states.
Select the Freeze Frame button.
Select the Cursor 1 button.
Tap the screen to move the cursor to approximately the middle of
one of the high state pulses as shown at left.
The high state amplitude can be found in the box labeled Channel
A Amplitude. Write the amplitude below.
____________________________
Tap the screen to move the cursor to the middle of one of the
low state pulses.
The low state amplitude can now be found in the box labeled
Channel A Amplitude. Write the amplitude below.
____________________________
Ignore the number in the box labeled Time.
Deselect the Freeze Frame button.
Leading Edge
Trailing Edge
Pulse Width
High State
Low State
Period
Cursor 1
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DSO WBT Function Generator Exercise
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14. Next, measure the pulse width of the signal.
Select the Freeze Frame button.
Select the Cursor 1 button.
Move Cursor 1 to the left of the leading edge of one of the
pulses and then use the Cursor button to move it to the right until
the box labeled Channel A Amplitude starts to increase. You arent
worried so much about the amplitude other than to see where it
begins to increase. This is the point where the signal turns
on.
Ignore the number in the box labeled Time.
Go to the next step.
15. Select Cursor 2.
Move Cursor 2 to the left of the trailing edge of the same pulse
and then use the Cursor button to move it to the right until the
voltage display labeled Amplitude Diff. A starts to decrease.
Again, you arent worried about the amplitude other than to see
where it begins to drop. This is the point where the signal turns
off.
The box labeled Time Difference is the pulse width of the
signal. Read the pulse width and write it below.
____________________________
Cursor 1
Cursor 2
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DSO WBT Function Generator Exercise
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16. While the previous waveform had a low
frequency, the next waveform has a high frequency. Start by
resetting the DSO to its default values. The easiest way to do this
is to exit and restart the DSO.
Select Go To
Select Exit
Select Test Instruments and start the DSO
Leave the DSO 1 leads in the same positions as the previous
steps.
17. To configure the Function Generator:
Turn the Coarse Frequency knob to 100K. Leave the other knobs
and switches in the same positions as they were in the previous
steps.
18. The DSO should look like the screen shown at left. To
configure the DSO to display this waveform:
First move or remove the Channel B waveform from the screen
using one of the methods shown previously.
Even though this is a high frequency pulsed signal all you see
is a flat line for Channel A. This is because the default time and
voltage settings are too slow to display the individual pulses of
the waveform. You dont know how to set the time and voltage
divisions. You could experiment manually, but there is an easier
way. When trying to configure the DSO for an unknown signal, use
the Auto Setup mode.
Select the Measuring Mode button.
Select the Auto Setup button. It takes a few seconds for Auto
Setup to run
When Auto Setup has finished, the measuring mode changes to Auto
Level.
Channel A
Channel B
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DSO WBT Function Generator Exercise
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19. Your screen should look like the screen shown at left. Now
it is time to practice the skills you learned previously.
Change the voltage division to make the waveform appear as large
as possible in the screen. You need to move the zero point in the
waveform so that the waveform does not display above or below the
top or bottom of the screen.
After completing the previous step write the final voltage
division of the waveform below.
____________________________
Change the time division to display at least 5 readable pulses
(that are not compressed) on the screen. Write the time division
below.
____________________________
Measure the high state amplitude and write it below.
____________________________
Measure the low state amplitude and write it below.
____________________________
Measure the pulse width of the waveform and write it below.
____________________________
20. Turn the FG-500 OFF.
Congratulations! This completes this portion of the DSO WBT.
Please take the on-line assessment to get credit for the WBT. You
will need the answers from this exercise to take the on-line
assessment.