User:John Callow/Notebook/Junior Lab 307/2009/09/02

From OpenWetWare
Jump to: navigation, search
Owwnotebook icon.png Project name Report.pngMain project page
Next entryResultset next.png
SJK 23:00, 15 September 2009 (EDT)
23:00, 15 September 2009 (EDT)
Very good primary lab notebook for this lab. Good use of pictures (which you say you're going to ramp up!) and the embedded spreadsheet). The main thing I'd like to see is more commentary and more notes. So, keep trying to record as much information as possible while you're working. I think including more photos like you said will entice you to do that anyway.

Oscilloscope lab

lab manual used

Only did up to the part on AC coupling.

link to my summary

Equipment

SJK 22:33, 15 September 2009 (EDT)
22:33, 15 September 2009 (EDT)
Good job recording the exact model numbers of equipment used. Love the use of a picture, too!

BK precision 4017A 10MHz Sweep/Function Generator

Tektronix TDS1002 two channel Digital Storage Oscilloscope 60MHz 1GS/s

BNC cable

Setup

My setup

The only setup required was connecting the sweep/function generator's output to channel one on the Oscilloscope.

Safety

For the experimenter

-The only major danger in this lab is from being shocked from a wall outlet or cable connected to it from equipment. Before plugging anything in check to make sure the wires aren't damaged or exposed.

-If something appears broken label it in some way so that others after may see right away.

For the equipment

-Check that the BNC cable is connected correctly before turning anything on.

-Make sure all of the equipment is in a stable position and if it needs to be carried to be cautious as fall damage is one of the biggest risks in this lab. In general keep the area of work organized and clean.

-Check what the equipment you use is rated to handle. If using the same equipment as listed the wave generator comes no where near the max voltage of the oscilloscope so using the two together doesn't create a problem.

Basic waveform measurements

SJK 22:37, 15 September 2009 (EDT)
22:37, 15 September 2009 (EDT)
Nice spreadsheet. One small tip: you could put the units in the column heading (e.g. "Period using grid (ms)" and then you can put just numbers in the cells. This makes calculations easier.

{{#widget:Google Spreadsheet

key=ttgzxr2a_zsmMmvw61ylxEw width=760 height=200

}}

Notes on triggering

Triggers are used to get a nearly unchanging view of the waveform

Types on the Tektronix TDS 10002

Edge - detects when the wave hits a certain voltage in a specified direction on the wave

video - extract synchronizing pulses from video formats such as pal or ntsc

pulse - Unsure of how this functions.

Info on triggering from this article on triggers for oscilloscope

AC Coupling

AC coupling may be used to remove DC from the signal. For this section of the lab this allows for the viewing of small changes or the fall time of the capacitor.

Using the cursors I found the time to go from peak to 10% to be 51 ms and using measure found 52.76ms. As a warning if using measure, it will measure what is viewed on screen so make sure the part being measured are viewable and the only thing on screen or it will also include the drop off it measures from oscillating.

Using the value from the measure function on the oscilloscope I found the rc constant to be

RC = time/2.197 = .5276/2.197 = .2401 seconds.

This formula found at http://en.wikipedia.org/wiki/Rise_time.

Sources of error

For the first part of the lab error in using the grid or cursors were likely due to difficulty either seeing markers or miss counting when using the grid and lining up the cursors correctly. All three methods of measurement came to similar results though and so are likely fairly reliable.

As mentioned above in the section on AC coupling not having the screen view set properly will cause the measure function to have error if only wanting to measure a specified part.SJK 22:49, 15 September 2009 (EDT)
22:49, 15 September 2009 (EDT)
Good qualitative discussion here. Starting with the next lab, you'll begin being more and more quantitative. For example, reporting mean +/- standard error of the mean.