SJK 00:56, 15 September 2009 (EDT)
00:56, 15 September 2009 (EDT)
Overall, you have a very good primary lab notebook and lab summary. You can see the comments on these two pages, plus some comments on Tom's page to see what you can improve on. In addition to the good written work, I am liking the energy you and Tom have in the lab and your willingness to try out things with the wiki and the equipment. I like it!
SJK 00:51, 15 September 2009 (EDT)
00:51, 15 September 2009 (EDT)
Excellent job putting in the exact model numbers, and the picture is great! Picture would be the best way of figuring out what you did if you were to read this a year from now.
- Tektronix TDS 1002 Oscilloscope
- Wavetek Model 180 Function Generator
- Short BNC Cable
Setting Up the the Oscilloscope
- We connected the BNC cable from the Lo output on the function generator to the CH 1 input on the Oscilloscope. The Ch 1 is set for DC coupling, with the volts/division set to coarse. The trigger is rather confusing at this time, but we found that the best setting for viewing a stable sine wave is auto trigger with an edge type. On the function generator, we multiplied the wave by 2 with the large dial, left the freq multiplier on x1 setting. We experimented with the sweep features, but i proved itself to be useless for this lab, so we left it off. The DC offset was left at 0.
First we take initial estimates of the amplitude using the boxed grid on the oscilloscope and estimated roughly 280mV.
We used the cursor (type: voltage) and the measure function on the oscilloscope to measure the wave amplitude more accurately, the result for both were 284mV. We repeated for several measurements, listed below..
There are multiple settings for the triggering on the oscilloscope, the wikipedia article about oscilloscopes outlines multiple types. One of the most common is the Rising edge setting. From the wikipedia article, the different types of triggers we used are summarized below.
- Rising Edge Trigger- This trigger causes a pulse every time the voltage hits a specified threshold. Although we used it for rising voltages, it can also be set for falling voltages.
- Video Trigger- This trigger extracts pulse information from a video feed (such as a PAL or NTSC format).
- Pulse Trigger- This trigger allows the user to specify a pulse width, causing the trigger's pulses to synchronize with the signal's pulses.
AC coupling is the process in which the DC component of the signal is removed via capacitor. The DC component can act as an offset for the signal, resulting in a less clear display of the signal. Blocking the DC component results in a better display, thus resulting in better measurements.
SJK 00:54, 15 September 2009 (EDT)
00:54, 15 September 2009 (EDT)
At this point (AC Coupling), you don't seem to have as much information recorded in your lab notebook as you did prior. I think this probably reflects the fact that you were not quite as sure of what you were doing. Definitely always try to take the time to write down as much details as possible, even when you're struggling to figure out the apparatus...it's usually going to help you out taking the time to write!
Measuring Fall Time
With the function generator set to square wave, zero offset, and a wave of amplitude approximately 13.2 V, we used the measure function to find out the fall time of the voltage from the peak to 10%. Our recorded value was 56 mS.
In order to calculate the RC constant, we used the following equation from wikipedia.
where is the rise time. We calculated the RC constant to be 25.5 ms.