User:David J Weiss/Notebook/notes Oscilloscope

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OSCILLOSCOPE

SJK 13:12, 15 September 2009 (EDT)
13:12, 15 September 2009 (EDT)
Overall, I think you did a good job in class learning how to use the oscilloscope. This page (your primary lab notebook) is pretty good, but I want to urge you to include even more detail in the future. Keep striving to take a lot of notes while you work, including commentary as you did here. The main issue with the lab overall is that you did not have a separate lab summary that I could find! Hopefully this became clear after lecture yesterday. The Oscilloscope lab page described what I was looking for. In future labs, you should have a separate page for your informal summary and for your primary lab notebook. See Tom's primary notebook page for a good example of a primary notebook and Anastasia's informal summary page for a good example of an informal summary.

notes on experiment

In this lab the main focus is to get familiar with the oscilloscope. The way to do this is to see how it works and how to use it. The means by witch we do this is by seeing how the interments functions in different modes and how changing the different functions changes the way data is changed.

safety

SJK 13:05, 15 September 2009 (EDT)
13:05, 15 September 2009 (EDT)
Good job here.

The safety concerns associated with this lab are mostly electrical. The main concerns with this lab are that the equipment is functioning properly and that there is no damage to the associated power connections.

Equipment

SJK 13:06, 15 September 2009 (EDT)
13:06, 15 September 2009 (EDT)
Good job including exact model numbers of equipment. In the future, including pictures is even more helpful in terms of conveying to someone (including yourself) what kind of setup you had. If your phone doesn't do photos/email, you can ask another student or me to help out if you want.

The equipment used in this lab is as follows: 1) Textronix TDS 1002 Two Channel Digital Storage Oscilloscope 2) 60 MHz 1GS/s Wavetek Sweep/Function Generator Model 180

Set Up

Set up of this lab was pretty basic. It involved plugging in the Oscilloscope as well as the Function Generator,and turning the power on both. After this you will need to connect the two with BCN connectors (BCN connectors are used on the ends of coaxial cables to attach two pieces of equipment) so that the Oscilloscope can interpret the signals from the function generator.

Day One

On the first day of the lab I worked with Cristhian Carrillo and we basically were just trying to figure out how the equipment worked and tried to do the first couple of parts of the experiment, but we ran into some difficulty in getting the wave function to display properly and had to get some help from Dr. Koch and our T.A. Pranav Rathi who were extremely helpful in understanding how the equipment worked but as time was running out no data was recorded.

Day Two

On the second day of the lab i worked with Elizabeth Allen. We set up the equipment and started doing the experiment. The first thing we did was to set up the wave function generator to produce a sine wave but we had some trouble due to the fact that the DC offset was shifted and had to adjust the wave of fit the screen. We then started to adjust the triggering functions and found that it controls where the wave is first displayed on the screen. when set to trigger within the waveform it stabilized the wave and freezes it instead of having a continuous function. we then changed the wave generator to produce square waves. these waves could be distorted when we changed the coupling from ac to dc. the dc coupling function would display the square wave without any distortion but when the coupling is set to ac coupling the wave is distorted on the horizontal sections due to overshooting the peaks of the function. when we adjusted the the grid to display the region where the function was overshooting were able to measure the fall time of the wave.

Basic Waveform Measurement

SJK 13:08, 15 September 2009 (EDT)
13:08, 15 September 2009 (EDT)
There is a good amount of information in this section, so that I can understand what you did.

We set the function generator to output a sine wave at 1KHz and tuned the frequency to 200Hz, then centered the wave on the grid with vertical grid divisions of 5.00V and horizontal grid of 5ms due to the chosen frequency.Estimating by sighting on the grid we found an amplitude of 6V. Using the Measure function gave us a Pk-Pk measurement of 11.8V.The cursor function opens a menu that allows to measure by time or voltage.

Triggering

We could adjust the triggering to the rising slope through the trigger menu function. Triggering on the rising edge is when the wave begins to form on the display. The rising edge of a wave form is on the left edge of the display and at the trigger point markings. When switching to falling moves the wave across the screen until the edge of the wave is at these points.

AC Coupling

SJK 13:10, 15 September 2009 (EDT)
13:10, 15 September 2009 (EDT)
I think your error here (which I can deduce because you took good notes, thanks!) is that you measured the time to get to zero, as opposed the time for it to fall from 100% to 10%. Technically for an exponential, if you have infinite resolution it will never get to zero. So, what you end up doing is not a useful measurement if you try to find the time to reach zero.

The DC voltage is increased by the output level of the function generator. The DC coupling displays the basic wave form, whereas the AC coupling displays the ripple on the DC voltage. the square wave generated by the function generator allows for the measurement of the fall-time. This can be done by changing the coupling to ac while generating a square wave and adjusting the parameters of the display to show the modified square wave and measure the time it takes to go from the peak to zero. The time we measured was about 2.3 ms at 200 Hz and 293 ms at 1 Hz. Looking at the wiki article about rise-time tr to be approximately 2.179 Tao, where RC is constant. Fall time is extended by the delay in the signal display that is inherent in the way that the signal is processed by the oscilloscope which creates an inflated value for the fall time.

Links

Physics 307L

David's Homepage

David's Course Page

David's Lab notebook

wiki article rise time