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EXAS
I
NSTRUMENTS
I
NCORPORATED
G
ETTING
S
TARTED WITH
CBR
7
Hints for effective data collection
(cont.)
The clear zone
The path of the
CBR
beam is not a narrow, pencil-like beam, but fans out in all directions up
to 10° in a cone-shaped beam.
To avoid interference from other objects in the vicinity, try to establish a
clear zone
in the
path of the
CBR
beam. This helps ensure that objects other than the target do not get
recorded by
CBR
.
CBR
records the closest object in the clear zone.
Reflective surfaces
Some surfaces reflect pulses better than others. For example, you might see better results
with a relatively hard, smooth surfaced ball than with a tennis ball. Conversely, samples
taken in a room filled with hard, reflective surfaces are more likely to show stray data points.
Measurements of irregular surfaces (such as a toy car or a student holding a calculator while
walking) may appear uneven.
A Distance-Time plot of a nonmoving object may have small differences in the calculated
distance values. If any of these values map to a different pixel, the expected flat line may
show occasional blips. The Velocity-Time plot may appear even more jagged, because the
change in distance between any two points over time is, by definition, velocity. You may
wish to apply an appropriate degree of smoothing to the data.