Allen-Bradley 2755 User Manual download pdf (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

1000

of an inch (0.0254 mm).

Apparent

lement

Wid

1 2 ... 27 28 29 30 31 32 33 34 35 36 37 ... 95 96

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Allen-Bradley 2755 User Manual Page 32