C
OPYING PERMITTED PROVIDED
TI
COPYRIGHT NOTICE IS INCLUDED
© 1997 T
EXAS
I
NSTRUMENTS
I
NCORPORATED
G
ETTING
S
TARTED WITH
CBR
9
Hints for effective data collection
(cont.)
Smoothing
Smoothing capabilities built into the
RANGER
program can reduce the effect of stray signals
or variations in the distance measurements. Avoid excessive smoothing. Begin with no
smoothing or
LIGHT
smoothing. Increase the degree of smoothing until you obtain
satisfactory results.
0
For an activity with a higher-than-average likelihood of stray signals, you may wish to
increase the smoothing on the
SETUP
screen before sampling (see page 38).
0
For already-collected
REALTIME=NO
data, you can apply smoothing to the data. The
calculator must be connected to the
CBR
. Choose
PLOT TOOLS
from the
PLOT MENU
,
choose
SMOOTH DATA
, and then choose the degree of smoothing.
Noise—what is it and how do you get rid of it?
When the
CBR
receives signals reflected from objects other than the primary target, the plot
shows erratic data points (noise spikes) that do not conform to the general pattern of the
plot. To minimize noise:
0
Make sure the
CBR
is pointed directly at the target. Try adjusting the sensor head while
viewing a
REALTIME=YES
sample until you get good results before collecting a
REALTIME=NO
sample.
0
Try to sample in a clutter-free space (see the
clear zone
drawing on page 7).
0
Choose a larger, more reflective object or move the object closer to the
CBR
(but farther
than 0.5 meters).
0
When using more than one
CBR
in a room, one group should complete a sample before
the next group begins their sample.
0
For a noisy
REALTIME=YES
sample, repeat using a higher degree of smoothing until you
obtain satisfactory results. (You cannot change the smoothing in the
DISTANCE MATCH
,
VELOCITY MATCH
, or
BALL BOUNCE
applications.)
0
For a noisy
REALTIME=NO
sample, you can apply a higher degree of smoothing to the
original data.
Speed of sound
The approximate distance to the object is calculated by assuming a nominal speed of sound.
However, actual speed of sound varies with several factors, most notably the air
temperature. For relative-motion activities, this factor is not important. For activities
requiring highly accurate measurements, a programming command can be used to specify
the ambient temperature (see pages 40–41).