Page 1 of 9 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, you re ready to perform the exercise! Continue to the next page.
Page 2 of 9 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.
Page 3 of 9 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.
Page 4 of 9 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.
Page 5 of 9 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. Let s 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 doesn t 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.
Page 6 of 9 Pulse Width High State Leading Edge Trailing Edge 12. Before proceeding, let s 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. Low State Period Cursor 1 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.
Page 7 of 9 Cursor 1 Cursor 2 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 aren t 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 aren t 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.
Page 8 of 9 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. Channel A Channel B 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 don t 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.
Page 9 of 9 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.