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Unformatted text preview: ow. The Guide Box will give you directions and tasks to perform. It will also tell you when to
select a command in the Command Panel. After selecting a command, it will “gray out” and
the next command will become available.
You can also print and/or quit from the Command Panel or abort your analysis and try
The primary data output you get is by generating pdf files of your results, so be careful not to
quit without printing pdf files or exporting your data to be emailed amongst your lab group. 220 APPENDIX: SOFTWARE Calibration
The first command is to calibrate the Magnetic Field Sensor. Before selecting this command, you need
to set the probe to the 6.4mT setting.
After selecting the "Calibrate Probe" command, you will be asked to do two
tasks. First, you will need to choose the quantity on the x-axis of your data
graph. This is accomplished by moving the cursor over to the word "meter"
in the red-colored area (shown below) and then pressing the mouse button. You should get a list of choices as shown to the right. By selecting any of
these units, you will be making a choice about what you wish to measure.
For example, if you choose to use "cm”, you will make a graph of magnetic
field strength as a function of distance (B vs. x). It is likely you will want to
choose a small unit (cm’s or mm’s) to measure the distance in, since many
magnetic fields are not very strong over long distances Selecting "degree"
will make a plot of magnetic field strength as a function of angle (B vs. ).
Click "OK" when you are ready to proceed.
Second, you will need to eliminate the effect of the
background magnetic fields. This process is called
"zeroing the Hall probe" in the Guide Box. Place the
magnetic field sensor wand in the position you would
like to take your measurement, but be sure that there are
no magnets nearby. Note that power supplies and
computers generate magnetic fields, so it is a good idea to
keep away from them! When you are ready, select the
"Set Probe Zero" as shown below. Then select the “Done”
button. The calibration process is now complete.
This type of analysis relies on your graphical skills to interpret the data. You should be
familiar with both appendices, A Review of Graphs and Accuracy, Precision and
The first task is to enter your prediction of the mathematical function you expect to represent
your data. Making a prediction before taking data is the best way to determine if anything is
going wrong (remember Murphy’s Law). It’s also a good way to make sure you have learned 221 APPENDIX: SOFTWARE something, but only if you stop to think about the discrepancies or similarities between your
prediction and the results.
In order to enter your prediction, you first
need to decide on your coordinate axes and
scale (units) for your measurements. Record
these in your lab journal.
Next, you will need to select the generic
equation, u(x), which describes the graph
you expect for the data. Clicking the
equation currently showing in the box will
bring up a list of equations to choose from;
see the diagrams to the right.
After selecting your generic equation, you
need to enter your best approximation for
the parameters A, B, C, and/or D. These
values should come directly from your
prediction equation you did for class. As
you enter these values, you should see the
red line in the "Plot" box changing.
Once you have selected an equation and the values of the constants are entered, your
prediction equation is shown on the graph on the computer screen. If you do not see the
curve representing your prediction, change the scale of the graph axes or use the AutoScale
feature (see Finding Data below). When you are satisfied, select the Accept Prediction option
from the Command Panel. Once you have done this you cannot change your prediction
except by starting over.
After you have entered your prediction, you can explore the limitations of your magnetic
field sensor before you take data. The value of the magnetic field strength is displayed
directly under the Guide Box. When you are ready to take data, select Acquire Data from the
Collecting data requires that you enter the x-axis data before the computer reads in a value
for the magnetic field strength. You enter this data using the panel shown. For every x-axis
data value you enter, the analysis program will record the magnetic field strength in gauss on
the y-axis of the "Plot". Press "OK" to collect the next data point. 222 APPENDIX: SOFTWARE Each data point should appear on the graph on the computer
screen as you take it. If it doesn’t, adjust the scales of your graph
axes or use the AutoScale feature (see Finding Data below). If you
are satisfied with your data, choose Analyze Data from the
Finding Data on the Graph
You can find your data on the graph by adjusting the scales of your X-axis and Y-axis plots
manually. This scaling is a...
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- Spring '14