User:Daniel T Young/Notebook/Junior Lab 307L/2008/09/10

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SJK 13:31, 19 September 2008 (EDT)
13:31, 19 September 2008 (EDT)
Your lab notebook starts out very good, and then seems to taper a bit at the end, probably because you ran out of time. Good level of detail at the beginning. As noted below, key missing information about the equipement.


SJK 13:22, 19 September 2008 (EDT)
13:22, 19 September 2008 (EDT)
What were the exact model numbers and manufacturers of the o-scope and the function generator? This is key information to record! Also a link to the methods you're following.

Connected BNC to the function generator and Oscilloscope. Used auto set button to get a good view of my wave and changed function from the square wave to sin wave. After setting Frequency to 200 Hertz on the Wave function generator I found that my sin wave has gotten thinner so I adjusted the horizontal using the knob labeled position with arrows pointing up and down.

Using measurement button I view that all measurements are based off of Channel one while I am connected through channel 2. I change all measurement boxes so that they read the Frequency, period and Peak to peak. Here is how they read.

Basic waveform measurement

SJK 13:24, 19 September 2008 (EDT)
13:24, 19 September 2008 (EDT)
Really great data in this section! It's very easy to read, and you have uncertainties on your values. (Well almost all values have uncertainty.) Also, it's good how you note the mistake with 10x, but don't delete old measurements, you just correct them. Very good.

Reading One:

  Frequency- 200.5 ± 0.5 Hz
  Period- 5±.02 ms 
  Pk-Pk= 224V  
 (discovered that 10x multiplier was on giving actual pk-pk voltage of 22.4)

and we know that Pk-pk/2= Amplitude= 112V=Voltage from Function Generator (actual amplitude=11.2V)

Changed function generator values a bit. Output level set to about half original value. Frequency set to 100 Hz

Reading Two

  Frequency=100.6 ± 0.1Hz
  Period- 3±.05 ms 
  Pk-Pk= 11.6 (therefore Amplitude is 5.8V)

Changed output to about half of that from reading two. Frequncy set to 1000Hz.

Reading three

  Frequency=1000 ± 2Hz
  Period- 1±.002 ms 
  Pk-Pk= 5.64V (therefore Amplitude is 2.82V)


Checking the triggering menu found that edge is the most applicable for DC currents. Triggering is a useful way to explore a wave when we have high time resolution. Also, depending on the triggering setting we can start the oscilloscope reading on the fall of the rising part of our wave which is helpful for viewing half a period for measurement of amplitude or time using cursors as we will explore later in the lab.

AC Coupling

SJK 13:28, 19 September 2008 (EDT)
13:28, 19 September 2008 (EDT)
Looks like good measurements here, but including observations about uncertainty is good too, if you don't have repeated measurements. Also, compared with above, you have less description of what you're doing, and thus a future reader would probably not understand what you did, even though it's good that you have links to the article describing the method

Set the Amplitude/Voltage to 8.6 Volts and turned off DC offset. Also we set function generator to square wave. At extremely low frequency and high DC input with AC coupling set we get a wave representing a repeating exponential decay.

Measurement 1

Using cursors -

  Cursor 1 200e-3 V
  Cursor 2 22V

90% point = (22V-200e-3 V)*.9=19.62 10% point = (22V-200e-3 V)*.1=2.18 fall time= 47.2ms

SJK 13:36, 19 September 2008 (EDT)
13:36, 19 September 2008 (EDT)
This is the wrong equation! Check the t=0 and t=∞ limits and you'll see it's a rising exponential
Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "":): {\displaystyle V(t) = V_0(1-e^{-\frac{t}{\tau}})\quad\iff\quad\frac{V(t)}{V_0}=(1-e^{-\frac{t}{\tau}})}

[Fall Time Equation taken from here]

Thanks to Dr. Koch's observations I realized that my equation for fall time was incorrect. The actual equation is K=-t./log(V./Vo) and so with the code corrected my actual value for K is

      K =0.0228

Measurement 2

Using Measure command


27.2 / 2=Amplitude=volts= 13.6 ± .2V

SJK 13:26, 19 September 2008 (EDT)
13:26, 19 September 2008 (EDT)
I'm guessing you ran out of time here, as I don't see the fall time from "measure" function