Rockwell Automation 2755 High Performance VLD Scanner - Manual (Page 29)

3–16 Installation Considerations
For example, a 10 mil (0.25 mm) symbol with 0
_ pitch can be
scanned at 17 inches (43.2 cm) with a Catalog No. 2755-LD8C1
scanner. If you pitch the symbol 30
_ and determine the apparent
minimum element width using the formula below, the apparent
element width is 8.6 mils (0.22 mm).
Apparent Minimum Element Width = Actual Element Width x Cosine (Pitch Angle)
In the above example, the following conditions apply:
Actual Element Width = 10 mil (0.25 mm)
Pitch Angle = 30
_
Therefore: 10 x (cos 30
_) = 8.6 mil (0.22 mm)
The minimum recommended bar width that the Catalog No.
2755-LD8C1 scanner can read is 9 mil (0.23 mm). Because of the
pitch of the symbol, you need to use the Catalog No. 2755-LD8B1
scanner. However, the distance between the scanner and the symbol
is decreased. The maximum read range of the Catalog No.
2755-LD8B1 scanner for a 8.6 mil symbol is 13 inches (33 cm).
In summary, increasing the pitch of the symbol decreases the
apparent minimum element width. Figure 3.11 illustrates the
above example.
Figure 3.11
Effect of Pitch on Read Range
5
.13
10
.25
15
.38
20
.51
25
.64
30
.76
35
.89
40
1.02
45
1.14
50
1.27
5
12.7
10
25.4
15
38.1
20
50.8
25
63.5
30
76.2
35
88.9
40
101.6
45
114.3
50
127.0
Apparent Minimum Element W
idth
Mils
Millimeters
Inches
Centimeters
Read Range
(from scan window)
A
B
C
10 mil (0.25 mm) symbol with
30
_ pitch yields apparent
minimum element width of
8.6 mil (0.22 mm).
10 mil (0.25mm) symbol with
0
°
pitch.
Compensating for
Pitched Symbols