Campbell Scientific ID-2000W Software - Manual (Page 77)

8-1
SECTION 8. TROUBLESHOOTING
The following is a list of some of the more
commonly asked questions regarding ID-2000
features and procedures. Solutions and hints
for each are provided. It is recommended that
you look through these questions prior to calling
Technical Support to see if your particular
question has already been answered.
“I have a very large data file but I only want
to look at a small piece of it and do not want
to wait for the entire graph to be displayed.
How can I do this?”
There are two common ways to only display a
small portion of a data file. The first method is to
access the Edit Scales dialog and enter values
for Time Start and Time Stop if you know the
starting and stopping points you wish to plot. ID-
2000 will only plot data starting at the data point
corresponding to Time Start and stop plotting at
the data point corresponding to Time Stop.
A second method is to use the Quick Graph
feature which draws a quick representation of
the graph by only plotting selected data points.
Turn the quick graph feature on in the Plotting
Preferences dialog then go ahead and plot the
entire graph. When the graph has finished
plotting then turn off the Quick Graph feature
and zoom in on the section of data desired.
“I am manually scaling my graphs but the
scales are not the same as what I entered in
the Edit Scales dialog. What is wrong?”
There are conditions when ID-2000 will not use
the exact scaling numbers that you specify for
manual scaling. This is because ID-2000 will
not use non-standard scales. These types of
scales have grid intervals of an abnormal
number such as 3, 6, 7, 9, etc. or scales that
would result in partial grids being used at either
the top or bottom of the graph. ID-2000 uses
only intervals that are easy to read such as 1, 2,
5, etc. and always uses whole grids.
For example, let’s say you request scales of 3
for the min and 97 for the max. ID-2000 will not
produce a plot where the minimum scale is 3
and the maximum scale is 97. Instead, it will
calculate the closest min and max that could be
used and still produce standardized grid
intervals. In this example it would substitute
values of 0 and 100 in order to eliminate the
non-standard scales you requested.
“What is an integral and how does it work?”
If you plot an integral of a parameter you are
actually plotting the running total of the amount
of change in the parameter over time.
Let’s say that you have a data file of a race car
and one of the parameters in the file is Speed
which is speed of the car in miles per hour.
Now assume that you want to make a plot of the
distance the car travels over time but you don’t
have any Distance parameter in the file. By
using the integral feature in ID-2000 you can still
make the desired plot.
Without getting too complicated, think of plotting
the Speed parameter against Time. Now draw
small rectangles that are one second wide with
the bottom of the rectangle at 0 and the top at
the velocity value for that particular second. If
you do this for every second in the data file you
would have something similar to a bar chart
where the bars are touching each other. If you
added up the areas of each rectangle you would
have the distance traveled.
This is how the integral values of a parameter
are calculated. What you see on the screen is
the cumulative total of these areas at any given
point which in our example would represent
distance.
“How do derivatives work in ID-2000 and
why do they look so ”noisy"?"
The derivative of a parameter represents how
fast a parameter is changing over time. This is
the opposite of an integral which represents the
total amount of change over time. In our
previous example involving integration we
integrated the Speed parameter in order to
obtain distance that a car travels. If you plot the
derivative of the Speed parameter you obtain
the car’s acceleration. Or in other words, the
derivative of the Speed parameter is how fast
the car’s speed is changing which is
acceleration.