Physics307L:People/Le/Notebook/070827

--Linh N Le 15:59, 27 August 2007 (EDT)

see comment

Steven J. Koch 01:56, 29 August 2007 (EDT):That is great that you wrote down the model numbers and types of equipment that you are using!

Using: Tektronix TDS 1012 two channel digita storage oscilloscope and Heathkit ET-1000 Circuit Design Trainer

Basic Waveform Measurment

Sine Wave Freq ~ 100Hz

Using the Grid

• Peak to Peak Voltage: ~2.7V
• Period: 10ms

Using the Cursor

• Peak to Peak Voltage:
  • Top of Peak 1.40V
  • Bottom of Peak -1.32V
  • Delta V 2.72V
• Period
  • Frist Crest -7.20ms
  • Second Crest -17.20ms
  • Delta t 10.00ms

Using "Measure" Function

• Peak to Peak Voltage: 2.74V
• Period: 10.00ms

Now after changing the frequency, and changing the voltage by playing with resistors on the bread board

Sine Wave Freq ~ 500Hz

Using the Grid

• Peak to Peak Voltage: ~.8V
• Period: 2ms

Using the Cursor

• Peak to Peak Voltage:
  • Top of Peak .416V
  • Bottom of Peak -.40V
  • Delta V .816V
• Period
  • Frist Crest -3.560ms
  • Second Crest -1.560ms
  • Delta t 2.00ms

Using "Measure" Function

• Peak to Peak Voltage: .785V
• Period: 2.0ms

The only wave forms available to me were square, inverse sqaure, sinusoidal, and traingular. The oscilloscope was able to measure all of them, although resolution was bad in high frequency and low amplitude

AC Coupling

Applying a large DC voltage while measuring in AC allows me to look at the fluctuations that are caused by my DC powersource deriving its power from an AC source.

In DC mode, all I see is a straight line at the 12V mark. When I change it into AC mode, I can zoom in and look at the subtle fluctuations.see comment

Steven J. Koch 02:25, 29 August 2007 (EDT):Interesting...you are the second person to mention that "video triggering" helps to look at the noise on the ripple. I'm not sure why that is.

• Cycle RMS from 1.00mV to 2.00mV
• The triggering to look at the ripples is very sketchy. I found that Video triggering reduced alot of the "fuzzyness" and sometimes it would freeze the screen.

Measuring Fall Time

• Observing the square wave function in both AC coupling and DC coupling, I saw that the DC coupling was very square whilst the AC coupling decayed.

Fall Time w/Cursorssee comment

Steven J. Koch 02:27, 29 August 2007 (EDT):Hmmm...your numbers seem quite a bit different from other students and me(who were getting about 60 ms). It shouldn't depend on the fact that you were using the Heathkit, so I'm not sure why they are different. If this were a "real" lab, I would ask you to retake these measurements.

• Measuring from peak to about 10%
• DC Coupling
  • Peak 0s
  • 10% 1.080ms
  • Fall 1.080ms
• AC Coupling:
  • Peak -1.240ms
  • 10% -160.0 micro s
  • Fall 1.080ms

Fall time with "Measure"

• AC Coupling 3.50 micro s
• DC Coupling 3.24 micro s

RC Constant

The rise time is proportional to the RC time constant. (rise time)= (time constant) x ln(9). So, by measuring the rise time, we can find the time constant of the RC Circuit

Note: It was really had to measure with the cursors, since you had to eyeball the 10% mark. Also, doing that way, it is not apparent how the meter is able to get it down to micro seconds

FFT

FFT is a Fourier Function Transform. It is the principle that any wave front can be decomposed into many smaller, individual waves. Looking at the transform, I notice that many of the frequencies are near the start of the graph, and it thins out as it spreads further. The applet provided also reveals simular things. The waves that we can look at have "blurrier" starts and even out in the middle.

An FFT could be useful when trying to figure out what constituents make up a certain wavefront.

Oscilloscope Lab Summary

--Linh N Le 14:57, 31 August 2007 (EDT) 1. Brief summary of what you did (linking to the lab manual page is OK)

I tried to follow the lab notebook as best as I could. 
I had to be "creative" on some spots, since I had to work with different equipment.  

Click me to see the Lab!

• Add links to all wiki pages that contain your notebook entries. This is likely only one page.

Care to see my lab page?

2. Report your value for the fall time using AC coupling.

For the AC coupling, and using the "Measure" function of the scope, and manually with
the "Cursors" I got a fall time of 1.08ms.My time is a bit low compared to the others 
in the lab (about 60ms), so I should redo these measurements (if this was a real lab)

--Linh N Le 16:00, 3 September 2007 (EDT)

see comment

Steven J. Koch 00:44, 5 September 2007 (EDT):I agree! And since it's not a real lab I won't make you take more data :). For your grade, I will assume you reported a measurement with error estimates (and we will start discussing next week how to do this). My guess is that you were measuring the fall time on the DC coupled signal, not the AC coupled signal???

3. Include error bars!

 My measurements are so far off, that It wouldnt be worth discussing the error.
The data must be retaken 

4. Explain how you measured this (briefly)

 Using the "Cursors", I measured the time interval between the peak of the sqaure wave
and %10 from the bottom of the wave. To find the %10 mark, I measured the voltage of the wave
and lined up the %10 mark on the time measurements.Perhaps the measurements mave have been 
much better if I played with the resolution of the scales better (as Dr. Koch showed me during his "quiz").

5. What did you learn?

 I learned how to use an Oscilloscope and got to mess around with the Heathkit 

6.* It's OK if you didn't learn anything. But include things you are still confusing.

After having the "quiz" with Dr. Koch, I got a better feel for the machine, so if I had to do it again, it would be a much better run. see comment

Steven J. Koch 00:44, 5 September 2007 (EDT): I am glad you learned a lot about the 'scope and thank you again for being the person who had to use the heathkit! Your point is well taken and shared with others that the first lab was too long and didn't allow enough time for playing around. Hopefully having two weeks / lab will be better for the rest of the semester, but definitely keep suggestions like this coming!

7. What did you explore outside of the standard lab procedure? Anything interesting?

 I tried to play with the XY mode to make cool patterns, but my heathkit had no settings to
change the voltage easily 

8. What could make the lab better next year?

 Shorter lab, more time to play around, and enough equipment for eveyone