Rockwell Automation 2755-L7, -L9 Scanners - Manual (Page 19)

Chapter 3
Installation Considerations
3–6
When attempting to read a symbol that is pitched, two things must be
considered:
•
The adjusted minimum bar width
•
The nearest and farthest code elements must be within the scanners
reading range
Minimum Bar with Adjustment
When a symbol is pitched, the bars appear to be narrowerand closer to one
another. This apparent element width is a reduction of the actual element
width. Before you attempt to position your scanner using Figures 2.2 and 2.3
found in Chapter 2, you must determine your symbol’s adjusted minimum
bar width.
Figure 3.8 shows two boxes, each having the same bar code symbol printed
on them. Below each box is an exaggerated view of 5 elements (3 black, 2
white) as seen from the top down.
Figure 3.8
Actual versus Apparent Element Width
Pitched 30
°
Actual Element Width 21 mil (.53
mm) 0
°
pitch
Apparent Element Width 18mil (.46
mm) because of 30
°
pitch, elements
appear narrower
Actual Element Widths
21 mil
30
°
Apparent Element Widths
18 mil
Actual Element Widths
21 mil
Compensating for Pitched
Symbols