Physics307L:People/Meyers/Oscilloscope

Oscilloscope Lap Data
Set Up

We obtained the key equipment for the lab

1) An oscilloscope, Tektronix TDS 1002 Serial #: UNM JR Lab 004

2) A wave generator, B+K Precision 4017A Serial #: JR Lab FG 002

3) Several BNC cables

We then attached the BNC cables, one side into the output portion of the above mentioned wave generator and the other end into the Channel one portion of the above mentioned oscilloscope.

We then powered up the generator and oscilloscope and proceeded with the procedure outlined  here.

Measuring the sine wave

1) Using Grid Lines -- The grids were set to 1.04V intervals. Increased accuracy can be obtained by turning the Volt/Div knob on the oscilloscope.

2) Using Cursors -- Using the cursor function on the oscilloscope and dialing in the top and bottom cursors, manually, we were able to measure the peak, trough and difference in the sine wave. It should be noted that the cursors can be toggled to measure horizontally as well.

3) Using Measure -- Using the measure function does the same measure as does manual counting and the cursors but this eliminates the guess work and human error.

Triggering

Triggering on the Rising Edge -- The graph stops when pulse meets a rising voltage.

Edge Trigger -- The graph is a pulse when the signal crosses a specified threshold voltage.

Video Trigger -- The graph extracts pulses from video formats.

Delayed Trigger -- The graph waits a specified amount of time after an edge trigger before starting the sweep.

AC Coupling

1) When swapping from AC to DC coupling while in a sine wave, we found there was a phase shift of 680.0 micro seconds. The overall shape and frequency of the wave was unaltered.

2) Measuring the Fall Time

In the first week of the lab we set up a voltage divider as found here. Using this voltage divider, and with a capacitor in exchange for Z1, we tried to find the fall time of our system. Eventually, in the second week, we asked our class' TA Katie for assistance. She had us re-set up the generator and oscilloscope to look at a square wave, without the voltage divider. She then had us bring the frequency down to 10 Hz, where we noticed a exponential curve on our graph, that represented the discharge of the capacitor of our oscilloscope. We then measured the Voltage that the capacitor has before discharge and then when it is at 10% of that voltage. Afterward, we measured the time at both of those points and then put them into the fall time equation: V = V_initial*exp(t/tao) where tao is our fall time. Fall Time was 22.66 ms.

3) RC Constant -- Resistance*Capacitance; which is 22.66 ms.

4) Expected Fall Time Value -- is 10 ms as shown by Gibson in AC Coupling

Experimental Data

Basic Waveform Measurement

Sine Wave at 200 Hz with varying amplitudes

1)   Grid = 4.16 V   Cursor Measure = 4.16 V   Measure Function = 4.04-4.08 V

2)  Grid = 7.28 V   Cursor Measure = 7.28 V   Measure Function = 7.28 V

3)  Grid = 2.288 V   Cursor Measure = 2.25 V   Measure Function = 2.25

4) Large DC Offset Grid at 3 V per square  Grid = 7.2 V   Cursor Measure = 7.2 V   Measure Function = 7.2 V

AC Coupling

1) AC gives better view of ripples. Also, converting from AC->DC gives a time translation of 680.0 micro seconds.  Fall Time = 22.66 milliseconds   t1 = 0 ms   t2 = 21 ms   V1 = 4.37 V   V2 = 1.73 V

Error Analysis

We were not able to find any expected errors for either the oscilloscope or the wave generator.

However, Steve did tell use that the expected fall time would be around 16 milliseconds.

% error = (22.66ms-16.00ms)/16.00ms * 100 = 41.625%

Having only one source for this expected fall time means that the error may not be trusted.

Conclusion

1) We learned the basic workings of both the oscilloscope and the wave generator.

2) We calculated, three times, the voltage of a single sine wave.

3) We did the above mentioned measurements three more times.

4) We measured the AC to DC offset.

5) We lastly measured and calculated the fall time.

Special Thanks

1) Steve Koch- for good instruction and the expected fall time of the oscilloscope.

2) Katie Richardson- for exemplary aid in the lab on many of the procedure points.

3) Nathan Giannini- for help in the lab and much to do with the lab write up.