254764-001 Rev B 25
Sync Mode – Stationary Bar Codes
In this mode, a bar code(s) are placed in the beam and held in a known position. A sync input commands
the SV 2 Series to turn on the laser beam, perform a programmable number of scans, report the analyses
and turn off the laser beam.
A ~SA communication sync command is the most common sync source in this mode. A rastering laser
option is often used to analyze bar code area.
Note: The SV 2 Series must be programmed for Picket
Fence travel orientation in this mode if the bar codes are stationary when being scanned.
No Sync – Free Scan Operation
In this mode, a sync signal is not used and the SV unit scans and analyzes bar codes at random as they pass
through the laser beam. As stated in the Sync Input section, this mode is not recommended because it
cannot report on missing or undetectable bar codes that can be caused by printer or other system component
failures. This mode is most acceptable when the SV 2 Series is used as a bar code decoder only.
It is recommended to use serial communications to a host in this mode in order for the host to
determine missing codes.
If this mode is used, the SV 2 Series can still detect many print errors because of its partial decode analysis
capability. This algorithm can detect a bar code start or stop character and two adjacent characters. This
part of a code is usually present in most print failure situations.
For maximum reliability for partial decode analysis, the bar code(s) being analyzed must be present
in the laser beam for 10 scans (example: 100 milliseconds for SV units with 100 scans/analyses per
second performance). To calculate bar code travel speed in this mode, see the Bar Code Travel Speed
Considerations section. Calculate the maximum speed for the application per those instructions and
then divide the speed by two for this application.
PARAMETERS ANALYZED
For each bar code scanned and analyzed, the SV 2 Series performs practically all the ANSI, traditional and
laser based verification methods documented in industry specifications. All analysis parameters for these
methods are reported via serial communications (see Serial Port Transmission Format section) and most of
the parameters can be used in any combination to activate the five ports. The analysis parameters
performed are listed below in the same order of the standard transmission format as applicable.
Reference Decode
(ANSI method parameter)
Decodability
(ANSI method parameter)
Modulation
(ANSI method parameter)
Defects
(ANSI method parameter)
Edge Contrast
(ANSI method parameter)
Rmin/Rmax
(ANSI method parameter)
Symbol Contrast
(ANSI method parameter)
PCS
(Traditional method parameter)
Reflectance – Light
(Traditional method parameter)
Reflectance – Dark
(Traditional method parameter)
Ratio
(Traditional method parameter)
Average Bar Deviation
(Traditional method parameter)
Minimum Bar Deviation
(Traditional method parameter)
Maximum Bar Deviation
(Traditional method parameter)
Quiet Zone
(Traditional method parameter)
X Dimension
(Traditional method parameter)
