Welch Allyn SCANTEAM 3000PDF, Techical Manual, Page: 86 / 92

A–8
Technical Specifications
A.8 Bar Code Symbol Specifications
All bar code symbols should satisfy the appropriate AIM Uniform
Symbology Specification.
Background Substrate
The bar code symbol should be printed on material which is reflective
and has a matte (not glossy) finish. A background diffuse reflectance of
at least 70% to 80% is desirable for optimum contrast.
Ink Color and Type
The type of ink should be compatible with 660nm LEDs used in the
scanner. The bar code symbols inked bars should not exceed 10%
reflectance at 660nm which is being used for reading, whether printed
with black ink or colored ink.
Voids and Specks
The code should be printed clearly, free of voids, specks, blemishes and
lines which could “fool” the scanner. Specks or blemishes in the white
spaces, or false or missing bar sections could be interpreted by the
reading equipment as part of the code. Generally, the width of such flaws
is more serious than the height. Code symbols should be rejected if these
defects are present.
Definition
The bars in the bar code symbol should be well defined. Their edges
should not be rough or fuzzy, so that the bars and spaces have the proper
widths intended for the bar code symbology used. Since a scanner’s
aperture and resolution are chosen to comply with these widths,
definition should be sharp and consistent.
Tolerance
The ratio of the widths of bars and spaces in a bar code symbol must
conform to the appropriate AIM bar code specifications and can cause
problems if not correct throughout the bar code. Problems can occur
when bar edges are smeared or rough, or when they exhibit voids.