Physics307L F09:People/Phillips/Oscilloscope

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SJK 01:32, 20 September 2008 (EDT)
01:32, 20 September 2008 (EDT)
This is a very good lab summary and has all the necessary components. Probably your subsequent lab summaries will be a bit longer, because you will have more to report and discuss...but this one is great.

Firstly, here is my notebook entry, which shows my procedure, data, and observations:

Data & Summary

SJK 01:31, 20 September 2008 (EDT)
01:31, 20 September 2008 (EDT)
A few things strike me as very good in this section. First is your citation of Paul's notebook, which I was very happy with. You found a good way to find what you were looking for and then you gave credit to Paul -- these are great skills in science. Also, it is great that you have the uncertainty on your measurements, and even better that you discuss the uncertainty and the sources of them.

AC Coupling Fall Time

  • Using Cursors: 52±3 ms
  • Using Measure: 54±4 ms

These values were found by using the Cursor and Measure functions on the oscilloscope, respectively. The reason I have a lower uncertainty in my cursor time than the measure one is because it seemed rather easy to pinpoint where the cursor should go, leaving a narrow window of possible error, while the measure function seems to return values that are unsteady and tend to jump around with time, leading to a questionable certainty of measurement. To get error values closer to what they really are, I could repeat this experiment many times and make sure I get results within my limits. After taking a look at Paul's Notebook Entry, I found that this fall time corresponds to a τ value following this equation:

  • Vf=Vo·exp(-t/τ), with Vf/Vo=0.1 and t=53 ms (in between my two experimental values)
  • τ= 23.0 ms


I learned the basics of how to use an oscilloscope in this lab. I have a feeling this will be quite valuable for me in the future; it seems like quite a handy instrument. I didn't do much outside of the lab guidelines here on the wiki other than looking for an official value for the fall time (of which the search was unfruitful). It would have been cool to do the FFT part of the lab, but there simply was not enough time. Something I didn't like about it was that we didn't really know what we were doing until the end (or at least I didn't). Something that would have been nice is just more time for this lab. It would be great if next year's students could have 6 hours instead of 3, but I can see how it may be difficult for such a thing to occur.SJK 01:29, 20 September 2008 (EDT)
01:29, 20 September 2008 (EDT)
As for more time, many students have requested that, and it actually shouldn't be a problem next year. Even though the wiki accounts won't be available, students can still spend the first week playing around with the oscilloscope. I think this is a great idea and wish I would have recognized it earlier. As for not knowing what you were doing, I'm not sure my opinion on that yet...the discovery process is something I highly value in this course, but you may be talking about something different.