Physics307L F08:People/Barron/labsum~oscilloscope

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Oscilloscope Lab

SJK 01:16, 17 September 2008 (EDT)

01:16, 17 September 2008 (EDT)
This is a good summary overall. You do a good job of reporting the final results with uncertainty (but I think uncertainty is quite a bit off) and you have very good links to raw data. For future labs, you will also want to comment on your final values and what they mean (for example, comparison to currently accepted values).

In this lab, we basically learn (or relearn) how to use the basic features of a digital multimeter. (Steve Koch:I understand what you mean, but a multimeter is different than an oscilloscope.)

Here is the lab manual page.

Here are my lab notes.

The essential parts of the lab require us to measure waveforms, learn about triggering, observe differences between AC and DC coupling, and measure the fall time of a square pulse using AC coupling.

My procedure was as follows:

While performing the Basic Waveform Measurement SJK 01:14, 17 September 2008 (EDT)

01:14, 17 September 2008 (EDT)

, I neglected to save periodically. My browser timed out and I lost all my recorded data up to the Triggering portion.


I started out with edge, rising trigger @ 0.00 V. This projected the typical sin wave, with slope 1 @ t = 0. When I switched to falling trigger, my sin graph changed phase by pi, with slope -1 @ t = 0. Video trigger gave me a slowly moving double-wave - none of the options cleaned it up. Pulse triggering yielded more gibberish until I set the "when" option to ≠ instead of =. The Pulse Width was set to 1.00 ms, so the ≠ makes sense.

AC Coupling:

I set V amplitude to ~10 V. Switching to AC Coupling raised and advanced the whole function a very little bit in time.

I first measured the fall time incorrectly, setting my source's frequency too high. The second time around, I set the frequency to 7 Hz. This allowed me to see a more pronounced peak at the left side of the square pulse, which decayed nearly to 0 V before the end of the pulse. I used the cursor to measure the left side peak @ 8.60 V, the right side @ 600 mV. The manual wanted the fall time from max to 10% of max, so when I used the time cursor, I placed the second cursor marker @ the time for .800 V. The measured time was 62.00 ms. Using the equation V(t) = V0*(exp(-t/τ))...

Fall time = 62.00 ± .001 ms SJK 01:13, 17 September 2008 (EDT)

01:13, 17 September 2008 (EDT)
Where and how do you obtain this uncertainty? I don't see where it comes from, and also it is far too low. How would you get an uncertainty of .001 ms on a measurement of 62 ms (which I thought I saw in your notebook)...I think we should discuss this a bit in person next week as well

RC constant = τ = 26.1 ± .01 ms

This fall time is for ΔV = 8.60 V - .800 V ≈ 90.3% of the full change in V.

The most prevalent lesson from this particular lab is to save often, so my data isn't lost. Also, being prepared before the lab is important, because I spent a while correcting my openwetware account before even starting the lab.

In my raw data, I allude to pictures taken with my phone. This would enrich my reports/summaries, but unfortunately my phone doesn't pair with Mac computers. I may bring an actual camera in the future.

†(corrected from erroneous calculation in raw data)