254764-001 Rev B 41
~SBn
Normal or Single Scan Operation
When n=0, normal scanning is enabled where a code must be scanned 2 out of 3 times in order to be
detected.
When n=1, a single scan of can be used to capture and analyze a bar code, enabling bar codes to be
analyzed while traveling through the laser beam at high speeds.
The major trade-off to the single scan feature is only one bar code at a time can be analyzed in the beam vs.
up to 4 codes in picket fence mode in the standard system. The major disadvantage to this method in cases
where only a single scan is used for evaluation of a bar code is there is a higher probability that the analyses
may not be accurate because part of the scan could be at the upper or lower edges of one or more of the
elements in the code. Therefore if most of the analyses are being calculated with a single scan, this type of
operation is recommended for measuring print trends in high volume, high speed applications where some
small percentage of analyses that randomly indicate an unusual low grade can be filtered out.
In the case the bar code is in the laser beam for more than a single scan, all the scans gathered are averaged
in the symbol analysis just like standard SV operation.
The special single scan operation is enabled only in Ladder Orientation mode. Picket fence Orientation
mode operation is not affected. The travel direction of the codes can be either picket fence or ladder. The
reason for using ladder mode is it limits the number of codes that can be simultaneously analyzed in the
beam to a single code.
How to Set Up Single Scan Operation
Three commands that set up the operation are ~SB1 and ~LS01 and ~Hnx (x can be 2, 3, 4, or 5). The SV
must also be placed in “Ladder” mode and the code must be in the ladder zone to be scanned and analyzed.
~SB1 (~SB0 is the normal setting) enables the system to let the initial scan of a code pass to the analysis
algorithms rather than wait for one of the next two scans to be a duplicate before the code is allowed to be
analyzed.
NOTE:
The ~SB1 setting may not update the horizontal bar code position in the report transmission.
Therefore if the horizontal position is needed during setup, set ~SB0 temporarily to see the position, then
set ~SB1 for 1 scan operation.
~LS01 allows the initial scan to be reported as a 1 scan average in case the code leaves the beam before a
second scan is detected.
~Hnx is a command that programs the number of consecutive scans that do not detect a bar code that cause
the code to exit the beam and be reported. The standard system operation is fixed at 5. ~Hnx can be
programmed for 2, 3, 4, or 5 scans. A lower number will allow a higher duty cycle, but it may also be less
stable if a code is static in the laser beam, therefore causing multiple reports.
Note:
Especially when
setting up with a static code in the beam, or operating in picket fence orientation, make sure the code passes
through the programmed ladder zone.
Checking SV Status with ~HT
The normal way of checking system status is with the ~HT command. The newer commands ~SB and ~Hn
are not displayed with the standard ~HT command. In order to display the additional commands, set
command ~De1 to allow the alternate ~HT reply.
When using ScanVision menus to program SV parameters, set ~De0 for normal ~HT reply or an error
message may be displayed.
