PHY 2049L
Lab 6

Oscilloscope Measurements

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Updated: 2/2/2013
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Guiding Question:

The Summary of the Argument should also discuss the qualitative (visual) conclusions you reach about the behavior of the current when each of the circuit elements we use (resistor, capacitor, and diode) are connected to an AC voltage.

Preparing for the lab:

We will be doing "Lab 38" pretty much as described in the lab manual with some changes in what we will observe on the oscilloscope screen.

Answer the pre-lab questions on LON-CAPA after reading the background information on pages 379 through 381 in the lab manual. You should also look at the pictures of the actual oscilloscope display below and the diagram on LON-CAPA.

Hint: You must read questions 5 and 6 very carefully while thinking about how the oscilloscope screen would look when measuring a very large voltage (maximum + and - excursion of the trace on the screen) and one so small as to be barely visible (smallest visible deviation from a flat line, which will be about 1/5 of a 1 cm division).

I will go over some of the details of how to use the oscilloscope and interpret readings made on it at the start of class, but you should read the prelab and review additional info given here.

Comment

The data pages provide graphs that have the same number of major divisions as you see on the screen. Use them to make careful drawings, to scale, of what you see on the screen. They can also help you to visualize the situations needed to answer some of the prelab questions.

Pay attention to how the wave generator is hooked up to the frequency counter with a coax cable and then split to regular cables. (This part of the setup is the same as what we used last semester for the wave experiment.) You will have to hook it up yourself for the next lab.

See a separate page on use of the oscilloscope and its controls.


Apparatus

Picture of the oscilloscope in operation, connected by a coax cable to the wave generator and digital frequency counter above it. For this lab, you will find the equipment assembled like you see it here. For later labs you will have to make the connections yourself, so pay attention to how the wave generator and frequency counter are hooked up today.

oscilloscope with wave generator and frequency counter

The oscilloscope (bottom of the stack) is in operation, driven by the wave generator above it via a coaxial cable. Here we use a "tee" to send that same signal to the frequency counter (top) where another "tee" is used along with a splitter to provide a non-coax connection to the multimeter (which is in AC Volts mode). The reading of 7.07 V (rms) on the meter is about what you would expect from 20 V peak-to-peak (+10 V to -10 V) input. You can also see that the scope display is consistent with that same 10 V amplitude and the 5 ms period expected for a frequency of 200 Hz, although this is clearer in the higher resolution picture on the next page where the oscilloscope control settings are explained.

 
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