Rockwell Automation 2755 High Performance VLD Scanner - Manual (Page 17)

3–4 Installation Considerations
The LD4 scanners can read bar code labels at various distances
depending on the apparent minimum element width
➀ and scanner to
label pitch. The scanner can read labels within one of four read
ranges: A, B, C or E.
Figure 3.5 shows the reading distances for each range of the LD4
scanner. Table 3.A lists the read ranges for the LD4 scanners in
numeric format.
Refer to ”Compensating for Pitched Symbols” if your labels are
pitched.
Figure 3.5
Read Range vs Apparent Minimum Element Width (LD4 Scanners)➁
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
➁
1 mil = 0.001 inches ➂
➀
➂
➀
55
139.7
60
152.4
65
165.1
70
177.8
75
190.5
80
203.2
85
215.9
Read ranges based on four character, Code 39 labels with a wide to narrow bar ratio of 2.6 to 1 and a print contrast ratio of .75 or better.
Read ranges vary with bar code symbol quality.
For minimum element width, refer to ”Determining Apparent Minimum Element Width” in Chapter 3.
55
1.40
E
2755-LD4 Read Ranges