Physics307L:People/Harriger/Summaries/Lab 00

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Contents

Lab 00: Oscilloscope Exploration

Summary

SJK 22:01, 21 September 2010 (EDT)
22:01, 21 September 2010 (EDT)This is a good summary, Kirstin.  It's a nice discussion of what you did, and easy to read.  I was happy to learn that you learned a lot, despite never having used an oscilloscope or function generator before.  The links to your primary notebook and Brian's page are good.  The main thing that is missing and that will be essential for your future lab summaries is a quantitative estimate of uncertainty.  This is what we talked about on Monday, often reported as "+/-" error.  I do see your qualitative discussion of error, which is good.  In the rest of the summary, there are some things that are unclear or maybe incorrect.  For example, the DC component of a signal is not necessarily "noise."  Overall, very good summary.  I'll put notes also on your primary notebook page.
22:01, 21 September 2010 (EDT)
This is a good summary, Kirstin. It's a nice discussion of what you did, and easy to read. I was happy to learn that you learned a lot, despite never having used an oscilloscope or function generator before. The links to your primary notebook and Brian's page are good. The main thing that is missing and that will be essential for your future lab summaries is a quantitative estimate of uncertainty. This is what we talked about on Monday, often reported as "+/-" error. I do see your qualitative discussion of error, which is good. In the rest of the summary, there are some things that are unclear or maybe incorrect. For example, the DC component of a signal is not necessarily "noise." Overall, very good summary. I'll put notes also on your primary notebook page.

This lab covered the basic operation of the oscilloscope, a device which allows for measurements of varying voltages. We used a wave function generator, which generates a time varying electric signal, connected to the oscilloscope via a BNC cable, to create and analyze waves at different settings. The three wave types we could analyze were sine, square, and triangle waves. We used different ways to measure the amplitude and period of the waves: the measure function, the cursor, and counting the grid by hand.

Then we looked at a square wave with AC coupling and DC coupling. There is an AC and a DC signal from the function generator. AC coupling makes the signal go through a capacitor, which acts as a high pass filter and smooths away noise that is left in with the DC coupling. We measured the fall time associated with capacitor in the AC coupling with the measure function and using the cursors to isolate data points. The measure function on the oscilloscope gave the fall time as 37.1ms and we found the fall time to be 23.82ms based our calculations from the cursor measurements. In our work uncertainty was introduced by human error when taking measurements, truncation by the internal computer of the oscilloscope, and rounding error during calculation.

Analysis

From the cursor measurements, the fall time, τ, can be found using the equation:
V(t)=V_0 e^{ \frac {-t} {\tau}}

From the square wave we measured the following values with the cursor:
V1 = 7.2V,V2 = 4V,T1 = − 35.2ms,T2 = − 21.2ms

Using these values in this equation derived from the first:
V_2=V_1 e^{ \frac {-|T_2-T_1|} {\tau}}

τ is determined to be 23.82ms. This is 64% of the oscilloscope's value.

Conclusion

Having never seen an oscilloscope or a function generator before, I learned a lot about how they work and how to use them. I also learned how to use the OpenWetware site to keep a detailed lab notebook with much help from Brian.

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