Rockwell Automation 2755 AdaptaScan Bar Code Readers - Manual (Page 32)

Installation Considerations 2–6
An element is either a bar or space between bars in a bar code. The
maximum read range is determined by the narrowest element. If the
bar code symbols are pitched with respect to the Reader, the apparent
width of the bar code elements is reduced. This reduction in the
element width affects the read range. When using the Read Range
charts (page 2–8), use the apparent element width, not the actual
element width.
The apparent element width is calculated using:
Apparent Element Width = Actual Element Width x Cosine (Pitch Angle)
For example, two boxes are scanned at a 0 and 30
_ pitch. An
enlarged area of 5 elements (3 black, 2 white) are shown as they
would appear looking straight down the edge of the label.
Apparent Element Width
10 mils
Apparent Element Width
8.6 mils
30 _ Pitch
Actual Element Width
10 mils
Actual Element Width
10 mils
The apparent element width above was calculated as follows.
Apparent Element Width = 10 mil (0.25 mm) x Cosine (30 _ )
= 8.6 mil (0.22mm)
Element widths are usually described in mil units. A mil is
equivalent to
1 /
1000
of an inch (0.0254 mm).
Apparent Element Width