User:Jared A. Booth/Notebook/Physics 307L/2009/08/24

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Lab Summary
The peak to peak voltages of 4 different wave forms were measured and recorded as follows. '*The fifth wave was unmeasurable due to distortions caused by limitations of the oscilloscope.

Using a 5Hz frequency square wave, the fall time was measured to be 59.00ms, implying an RC constant of 26.85ms.

Equipment
Tektronix TDS 1002 Digital Storage Oscilloscope BK Precision 4017A 10MHz Sweep/Function Generator BNC Cable

Safety
The main safety concern in this lab is electrical shock as we will be using instruments plugged in to the 120V AC wall outlets. Make sure to check all chords for fraying or breaks before use. Also ensure that the BNC cable is properly hooked up.

Setup
Plug both the oscilloscope and the function generator into a 120V AC wall outlet and connect the BNC cable to the output of the function generator and the CH1 lead on the oscilloscope. Turn on both the generator and oscilloscope.

Waveform Measurments
'*The fifth wave was unmeasurable due to distortions caused by limitations of the oscilloscope.

Wave 1 Set the generator to a sine wave at 200Hz. Measure the peak-peak voltage: 7.52V --measured by grid 7.52V --measured by cursors 7.52V --measured by oscilloscope

Wave 2 Set the generator to a sine wave at 75Hz. Adjust the output level slightly. Measure the peak to peak voltage: 9.90V --measured by grid 9.84V --measured by cursors 9.84V --measured by oscilloscope

Wave 3 Set the generator to a sine wave at about 7kHz. Adjust the output to a high level. Set the oscilloscope to acquire an average of 64 samples to remove the fluctuations in the wave towards the peaks. Measure the peak to peak voltage: 19.52V --measured by grid 19.56V --measured by cursors 19.5V --measured by oscilloscope.

Wave 4 Set the generator to a sine wave at 500Hz. Adjust the output to a low level. 3.72V --measured by grid 3.76V --measured by cursors 3.76V --measured by oscilloscope.

Wave 5 Leave the generator at 500Hz. Adjust the output to an high level. Set the generator to a large positive DC offset. Note that with sufficiently high DC offset the waveform seems to be displayed improperly. Specifically, it appears that the oscilloscope does not measure above 13V. As the DC offset is lowered, the waveform returns to a sinusoidal wave.



Triggering
According to Wikipedia, modern oscilloscopes use triggered sweep "to display events with unchanging or slowly changing waveforms, ...[which] may or may not be evenly spaced." There are four types of triggering on the TDS 1002 Digital Storage Oscilloscope: Edge, Pulse, Video, and External.

Edge Triggering Edge triggering occurs "when the input signal crosses a specified threshold voltage in a specified direction." The TdS 1002 allows you to adjust between rising and falling voltage and to change the level of the threshold.

Pulse Triggering Pulse triggering allows the user to designate a delay after a specified edge trigger before triggering the oscilloscope. This is particularly useful in examining only certain portions of a wave function.

Video Triggering A video trigger uses a circuit which extracts from a video feed and can be set to trigger at specific points, such as every line, a specific line, every field, or every frame.

External Triggering External triggering uses a trigger input to detect a pulse from an external source for triggering.

AC Coupling
Set the generator to a 5Hz square wave and adjust the output to an 8.5V amplitude. The fall time was measured to be 59.00ms measured from the peak to 10% voltage using the cursors. Using this value, the calculated RC constant of the oscilloscope is $$RC \cong \frac{t_r} {2.197} = 26.85ms$$

Acknowledgments
T. Mahony's Oscilloscope Lab Book for page format. Wikipedia for information on triggered sweeps.

Links
Physics307L My OWW Page My 307L Page


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