Allen-Bradley 2-D User Manual page 123

Glossary G–9
Module
The narrowest bar or space (unit of measure) in a code. The term is
used by the Uniform Code Council in its description of UPC/EAN
code; it is also used in the description of Code 128. Contiguous
modules are used to form bars or spaces which are wider than one
unit.
Module Aspect Ratio
The ratio of height to width of the narrowest bar or space, or unit of
measure, in a bar code.
N
Nanometer
A unit of measure used to define the wavelength of light. Equal to
–9
10 meter.
Nominal
The exact (or ideal) intended value for a specified parameter.
Tolerances are specified as positive and negative deviations from this
value.
Nominal Size
Standard size for a bar code symbol. Most UPC/EAN codes can be
used over a range of magnifications (e.g., from 0.80 to 2.00 of
nominal).
Publication 2755-6.4