In this experiment, we will use triggering to make our wave form plots easier to understand. The Arbitrary Waveform Generator instrument on the Analog Discovery™ will be used to apply relatively rapidly varying wave forms to the oscilloscope. We will see that the high rate of change of these waveforms makes it difficult to interpret the waveform using our previous display techniques. We will then use triggering of the waveform to make the wave form easier to view and analyze.
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If you have completed the previous Oscilloscope project, and your circuit is still intact, simply:
Connect the terminals of Channel 1 (1+, 1-) to the LED terminals. (The negative terminals on the Analog Discovery are denoted by a white stripe, while the positive terminals are a solid color.)
Open WaveForms™ to view the main window.
Click on the Scope icon to open the oscilloscope instrument.
Click on to start acquiring data. (Make sure Waveform Generator is running as well.) The waveform should scroll past the screen. The time scale, however, makes it difficult to see details of the waveform.
Change the time base to 20 ms/div so that we can get a closer look at the features on the time waveform. At time bases below about 100ms/div, the display no longer shows the waveform propagating across the screen. Instead, it displays successive “snapshots” of the waveform. So now, although the time scale would allow us to see details of the waveform, the images presented are jumpy and don't really allow us to focus on the data.
Now change the time base to 10 ms/div. The signal becomes more spread out in time so that the features would be easier to measure, but the display updates so quickly that it's nearly impossible to read anything of use!
Change the Level to -2V and notice where the trigger point is relative to your new level.
Change the Condition to “Falling” and note where the trigger point is relative to the new condition.
Change where time = 0 is on the screen by clicking and dragging on the symbol at the top of the display window. Notice its effect on the displayed waveform.