User:Anastasia A. Ierides/Notebook/Physics 307L/2009/08/24

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Oscilloscope Lab
Partner: Alex Andrego

Set Up & Procedure

 * 1) Obtain oscilloscope (Tektronix TDS 1002), wave generator (BK Precision 4017A), and BNC cable
 * 2) Connect the oscilloscope to the function generator with the BNC one end in the scope's Channel 1 port the other on the Lo Output of the function generator
 * 3) Set the oscilloscope to display channel 1
 * 4) Turn off the variable volts/division and all magnification settings
 * 5) Set the channel 1 input coupling to DC, the trigger mode to auto, and the trigger source to channel 1
 * 6) Set the intensity control to a nominal viewing level and adjust the focus control for a sharp display
 * 7) Hook up the output of the function generator to the oscilloscope and set the output function to sine
 * 8) Begin measurements using the grid, the cursor, and "measure"
 * 9) Repeat the last step for different waves of various amplitudes and large DC offset

Measuring The Sine Wave
When using different frequencies we arrived at different values for each trial summarized in the following table:
 * 1) Counting Lines. The amplitude of the wave generated is two lines above the equilibrium, about 1V. We used the Volts/Div knob to adjust the size of our graph.
 * 2) Using The Cursor. Using the cursor we saw that it is 1.04V.
 * 3) Using Measure. Using the measure button the max value for the amplitude was 1.04V as well.
 * 4) Different Waves/Further Investigation:

Triggering

 * 1) A rising edge is the positive slope of the signal wave pulsed into the oscilloscope by an external source.
 * 2) Using different triggers:
 * Pulse basically allows us to view an instantaneous, unaltered pulse
 * Edge allows us to view the rising or falling edge of a pulse
 * Video allows us to view the whole unaltered pulse of both rising and falling

AC Coupling

 * According to the helpful sites mentioned on the Oscilloscope lab page, AC coupling allows only AC signals, blocking out DC signals using a capacitor and only the AC wave appears. DC coupling allows both AC and DC signals and the wave appears "sketchy".
 * With our observations when switching to DC we were able to view wave patterns of very low frequencies (<10 Hz) whereas with AC we were only able to view the higher frequency wave (~79 Hz) while the lower frequency wave was not visible. Therefore we have concluded that the AC coupling mode is better for viewing the rippling on the DC voltage.
 * Measure the "Fall Time" for AC Coupling
 * Our directions for this part were to set the function generator to output a square wave with zero DC offset and an amplitude of about 8.6 V. We used the cursors to measure the fall time, peak to 10% value, and then used the "measure" function to measure the fall time of the square wave.
 * Using Cursors for 10% Value
 * We measured 50.4ms by using the cursor menu and choosing the time function. We used the position tuning knobs to find reference points on the grid by moving the screen area. Our 10% value was approximately 2.12V but because our instrument couldn't approximate that exact value we ended up using 2.20V as a reference.
 * We measured 50.4ms by using the cursor menu and choosing the time function. We used the position tuning knobs to find reference points on the grid by moving the screen area. Our 10% value was approximately 2.12V but because our instrument couldn't approximate that exact value we ended up using 2.20V as a reference.


 * Using the Measure Function
 * Using the "measure" function on the oscilloscope and choosing the "fall time" option, we measured 83.8 ms as our fall time. There is no certainty as to why this value is larger than the cursor value, but we have been experiencing this problem with our machine throughout this lab. There must be some sort of error with the measure function and therefore we do not trust the value given here.
 * RC Constant
 * Using the fact that a capacitor charges at the same rate as it discharges, and according to the http://en.wikipedia.org/wiki/Rise_time article on rise time as well as http://www.kpsec.freeuk.com/capacit.htm, we find that the RC constant is RC<<T where T is the time signal implied by our results due to the resemblance of our screen of spiked charges and that of the circuits web page that we consulted.
 * The expected value of our fall time is given by:
 * $$-t\div \ln (V_f/ V_i)\equiv \tau$$
 * Where $$\tau$$ is the expected value, the ratio of $$V_f/V_i=0.1$$, and t is our measured value. So, plugging these values into the above equation we get:
 * $$\tau \simeq 21.9 ms$$

Oscilloscope Lab Summary
This is the link to my Oscilloscope Lab Summary: Oscilloscope Lab Summary

Acknowledgments
Of course my lab partner: Alex Andrego

And here are the websites that my lab partner and I found very useful:

Oscilloscope tutorial Triggers on Hobby.com Tom Mahony's Lab Book Paul Klimov's Lab Book Physics 307L Oscilloscope Lab Wikipedia Article on the Oscilloscope AC/DC Coupling Info from Zone.ni.com Circuit Info from Kpsec.freeuk.com


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