Rockwell Automation 2755 High Performance VLD Scanner - Manual (Page 27)

3–14 Installation Considerations
Example 2:
Increasing the conveyor speed in Example 1 to 300 ft/min. decreases
the minimum number of scans per symbol to approximately 3. This
value is below the recommended value of 5 scans per symbol making
the 2755-LD4C1 inappropriate. The label would have to be at least
1.6 inches tall to be read by an LD4C1 scanner.
To increase the number of scans per symbol for step ladder
applications,you can select a higher speed scanner or increase the
height of the symbol.
Selecting Higher Speed Scanner
The LD8C1 scanner has a scan rate of 500 scans/second. It reads 40
mil labels at a minimum distance of 10 inches.
To calculate the minimum number of scans per symbol use these
values:
A = 500 scans/second – 5% = 475 scans/second (minimum scan rate)
H = 1 inch
Z = 60 inches/second (equivalent to 300 ft/min. )
S = 475 scans/second x 1 inch / (60 inches / second)
S = 7.9 scans
Since S (scans per symbol) is greater than 5 and the application uses
good quality labels, the 2755-LD8C1 scanner is appropriate for this
application.
Because of the increased speed of the LD8 scanners, most high speed
step ladder applications will use this scanner.
Calculating Scans/Symbol