User:David M. Winborn/Notebook/Phsics307L/2008/09/10

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Oscilloscope Lab

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Sections

1)Triggering

  1. Re-read Wikipedia section about triggering
  2. Common way to trigger is on a rising edge (what does this mean?). What happens to the signal when you use different triggers?
     Be able to explain this orally. 

Triggering is a means for 'Snap Shotting' a waveform at or after a specific event. Triggering allows one to observe waveforms, regular pulses and non-periodic pulses in a manner that corrects for horizontal drift, which may occur when the timebase and input signal become misaligned.

Triggering on the rising edge means that once the input voltage increases to a predetermined threshold triggering will take place tracing out the remainder of the waveform until which point the event reoccurs causing a new trigger.

AC Coupling

Sometimes is a tricky concept.

  1. This Wikipedia article on capacitive coupling isn't too helpful
  2. Apply a large DC voltage to the oscilloscope input (we'll have to figure out how to do this). Compare DC coupling with AC coupling. You may need to adjust the triggering. Which mode is better for viewing any "ripple" on the DC voltage? %AC Coupling
  3.
     Using rising part of square wave to measure fall time
     Measure the fall time of the AC coupling
         * Function generator: Square wave; zero DC offset; amplitude about 8.6 V
         * Use cursors to measure fall time (peak to 10% value)51.2ms 19.53Hz
         * Use "measure" function to measure fall time %56.4ms +/- 1ms
  4. What RC constant does this imply? (See Wikipedia article on rise time)
  5. How does this compare with the expected value for the oscilloscope? (Can you find the answer on Google?) 

[edit] FFT (Optional)

  1. Find the frequency of a sine wave using FFT "Math" function
  2. Look at the harmonics in triangle and square wave
  3. Compare with what you see on this applet: Fourier series applet
  4. Be able to explain what is going on with an FFT and when it may be useful 

[edit] Other (Optional)

  1. Play with XY mode to make some fun patterns
  2. Build your own low or high pass filter using resistors, capacitors and breadboard.
  3. Download waveform using LabVIEW (C:\Documents and Settings\USER\My Documents\308L\TDS1002 Folder\TDS1002.vi) 

[edit] Summary


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