Rockwell Automation 2755-L7, -L9 Scanners - Manual (Page 46)

Glossary
G–8
pitch
1) Rotation of a code pattern about the X axis.
2) The normal distance between the centerline or adjacent characters.
pre–printed symbol
A symbol which is printed in advance of application either on a label or on
the article to be identified.
Print Contrast Signal (PCS)
A measurement of contrast (brightness difference) between the bars and
spaces of a symbol. A minimum PCS value is needed for a symbol to be
scannable.
PCS = (R
L
–R
D
)/ R
L
, where R
L
is the reflectance factor of the light
background and R
D
is the reflectance factor of the
dark bars. PCS values can be calculated and
displayed automatically on suitable instruments.
print quality
The complete analysis of a printed symbol with regard to reflectance
properties as well as bar and space resolution with regard to symbol
specification. The inter–relationship of printed material and imprinted
material that affects the optimum performance of the scanner.
proximity sensor
A method of object detection in which the source and detector are located on
the same side; the detector senses energy from the source which is bounce
back by the object being detected.
Q
quiet zone, quiet area
An area preceding and following a bar code symbol that contains no printing.
R
raster scanner
Also available as an optional raster assembly. Raster scanners are similar to
standard scanners. The beam still travels from left to right, but it now does
so in a sinusoidal, or top to bottom, pattern. This allows the scanner to see
different scan paths so if a bar is deformed or soiled in one place it may still
be read due to the sinusoidal sweep of the beam.
raster rollover
A reset of the raster mechanism that causes the rastering scan beam to
rollover, or continue its sweep, as much as 360
°
until it resets.