User's Guide

Operating the MC3000 2-19
Scanning within range brings quick and constant decodes; scanning too close or too far away prevents decodes. Move the
scanner closer and further away to find the right working range for the bar codes being scanned. However, the situation is
complicated by the availability of various integrated scanning modules. The best way to specify the appropriate working
range per bar code density is through a chart called a decode zone for each scan module. A decode zone simply plots working
range as a function of minimum element widths of bar code symbols.
• Angle
The scan angle is important for optimizing decode performance. When laser beams reflect directly back into the scanner
from the bar code, this specular reflection can “blind” the scanner.
To avoid this, scan the bar code so that the beam does not bounce directly back. But do not scan at too sharp an angle; the
scanner needs to collect scattered reflections from the scan to make a successful decode. Practice quickly shows what
tolerances to work within.
Contact the Symbol Support Center if chronic scanning difficulties develop. Decoding of properly printed bar
codes should be quick and effortless.
Laser Decode Ranges
The decode ranges provide the decode ranges for barcodes of specified densities. Figure 2-15 shows the laser decode ranges and
Table 2-7 on page 2-20 lists the scan ranges for the selected bar code densities. The minimum element width (or “symbol density”)
is the width in mils of the narrowest element (bar or space) in the symbol. The maximum usable length of a symbol at any given range
is shown below.
Figure 2-15. MC3000 Laser Decode Ranges
in.
cm
MC3000
5 mil
4.9
7.5 mil
10 mil
7.9
10.8
12.7
17.9
26.4
20 mil
40 mil
30.6
55 mil
W
i
d
t
h
o
f
F
i
e
l
d
Depth of Field
Note: Typical performance at 73˚ F (23˚ C)
on high quality symbols.
0
0
5
12.7
10
25.4
15
38.1
1.3
0
3
6
9
0
7.62
15.25
22.86
7.62
15.25
3
6
12 30.48
in. cm
22.869
30.4812
1.2
1.6
2.0
20
50.8
25
63.5
30
76.2
35
88.9
UPC A
1.4
2.4
3.4