PSC LazerData Series 9000E, Installation And Operation Manual

Page: 21 / 104

INSTALLATION
3-7
In addition to being the correct distance from the scanner, the scan line
must pass through the entire code symbol including the quiet zone at the
beginning and end of the code. The quiet zone is a white area at least
ten times the width of a narrow bar in the code. This is illustrated in
Figure 3-4 below.
Scanning Beam Position
Figure 3-4
The more times the scanning beam passes through the entire code
symbol, the greater is the probability of successfully reading the code.
Figure 3-5 shows a method of calculating the number of passes the
scanning beam will make over the code symbol for two orientations. In
order to perform this calculation the user must know the speed,
orientation of the code symbol ("Ladder" or "Picket Fence"), the distance
from the scanner to the code and the dimensions of the bar code. In
addition, the sweep speed of the scanner and the scanning beam width
must be known. The scan speed was specified when the scanner was
ordered. The beam width can be determined using Figure 3-3. If the
user has a choice of mounting orientation, data for both orientations
should be calculated. The orientation yielding the most sweeps over the
code should be used.