User:Justin Roth Muehlmeyer/Notebook/307L Notebook/OScope

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SJK 14:14, 17 September 2008 (EDT)
14:14, 17 September 2008 (EDT)
This is a good lab notebook, in that the level of detail is pretty good, with many of your measurements being described well enough that another person could replicate them. However, there are a few very important things missing. Most notably, you do not record the type of oscilloscope and function generator that you're using. This is key information to record in an experiment! Also, you do not link to the methods that you're following (the oscilloscope lab page or lab manual). Keep in mind the goal of taking good enough notes that someone else could repeat your measurements by reading your notes. As it stands, even you yourself would probably not have enough information to repeat things in a few months -- you'd likely forget the type of function generator and not remember where the methods were, for example. I think you'll easily be able to include this information in future labs, and combined with the level of detail you showed below, your lab notebooks will be very good. Make sure you do this with the Poisson lab next week!

Set Up

I set up my oscilloscope-function generator system by connecting the "hi" output on the funtion generator, with the Oscilloscope channel 1 input via a BNC cable with terminator ends to avoid unwanted reflections. Powering up the Oscilloscope, I was then asked to attain a sin wave at 200 Hz. ---

Wave Form Measurement

Being my first time using a frequency generator I really had to fiddle around before I was able to reach my goal of creating a 200 Hz Sine Wave. I finally realized that the frequency multiplyer was multiplying the value of the knob just to its left.

I chose the sine wave as my shape of choice, then setting the value to 2, and the frequency multiplyer so that it multiplies by 100, I was able to attain a sine wave of 200 Hz. Of course one can also adjust the amplitude on the function generator, and I did so for the wave to fit my screen. I also noticed that on the oscilloscope one can adjust the vertical position of the wave. I decided it was a good idea to put the signal's equilibrium position so that it is aligned with the x-axis grid line.

Measuring the Characteristics of the Sine Wave

SJK 14:07, 17 September 2008 (EDT)
14:07, 17 September 2008 (EDT)
You have a good level of detail in this section, it is easy to understand what you're doing.

a) Measuring the amplitude by use of the grid lines Note: 1 division of the grid line represents a difference of 2 V. This value is displayed at the bottom left corner. My amplitude is 6 gridlines high from peak to peak. This means my amplitude is 12 volts.

b) Measuring amplitude with cursor Selecting "cursor" button allows me to use the vertical position knob to scroll a cursor of the range of my plot. Using this I validate the fact that my sin wave extends 6 V above equilibrium and 6 volts below equilibrium summing to an amplitude of 12 V.

c) Using Measure The measure button allows me to select on the display a number of functions for which the oscilloscope will display values. Selecting "peak-peak" validates once more a peak to peak difference of 12 V. I can also see my period, which is displayed to be 5.00 ms.

When we give it a DC off set the measure functions continue to measure accurately, so I now know that the measure functions give me results that do not depend on where the wave is on my display like the cursor does. This then is the best way to take measurements of the wave regardless of where it is on my screen.

The measure function continues to read and give good values for all the wave forms. ---


setting our vertical position to zero allows me to see how the triggering works. When I choose the trigger at a certain amplitude (voltage) what I receive back is the signal for which that amplitude occurs given the chosen slope. If I want to locate when the signal hits 2 volts on a rising slope, I am given a plot centered on the y-axis for that signal. Keeping all variables constant and changing only to falling slope will give me a plot with only a change in phase.

AC Coupling

SJK 14:09, 17 September 2008 (EDT)
14:09, 17 September 2008 (EDT)
In this section, it is good how you record how you're using 2 channels and the coupling on each, etc. However, one thing missing is a discussion of the uncertainty in your fall time measurements. This would be necessary when summarizing your data later to be able to put uncertainty on your "final" answer.

When applying a DC current by switching the funtion generator to DC and splitting our BNC cable into two channels I was able to compare the two types of coupling. I set channel 1 to AC coupling and channel 2 to DC coupling. Channel 1 gave me a very high resolution plot of the AC "ripple" that permeates the DC signal. This AC ripple is the noise in the DC channel. Channel 2 on the other hand shows me the DC current to a much less resolution, I cannot see the ripples to such an intense degree.

Measuring the Fall Time Set to square wave; zero DC offset; amplitude about 8.6 V. I had to really mess with the SEC/DIV to get the right time scale on the display.

Using the cursors: I put the first time cursor at the peak. The second cursor I put at the time at which that peak had fallen to about 10% of its original value. Delta then reads to be 39 ms.

Using the measure function the oscilloscope measures the fall time to be 44 ms.

RC Constant

According to wikipedia, the RC constant is equal to my fall time (measured to 10%) which was 44ms.SJK 14:06, 17 September 2008 (EDT)
14:06, 17 September 2008 (EDT)
I don't think this is correct (see other students' work). You should have linked to the wikipedia article you are using, so that I (and other future readers) would be able to check and see where the error may come from.