Rockwell Automation 2755 Atomscan Bar Code Scanner - Manual (Page 23)

Chapter 3
Designing the System
3–12
Step Ladder Applications
To calculate scans per symbol for step ladder applications, use this formula:
R x H
C
S = Scans per Symbol
R =
H = Symbol Height (length of bars of the symbol)
C = Conveyor Speed
S =
(must be at least 5)
Scan Rate
Conveyor Speed and Symbol Height must be expressed in similar units.
Calculations assume that the scanner and decoder are triggered for the entire
time the symbol is present and the symbol has a 0
°
pitch. (See the section at
the end of this chapter, Compensating for Pitched Symbols.)
Example:
A 40 mil bar code symbol that is 1 inch tall and 4.75 inches long is to be read
in step ladder orientation at 125 ft/min. Space is limited so the scanner must
be positioned as close as possible to the symbols.
Since the Scan Rate is measured using seconds, and the symbol height uses
inches, convert Conveyor Speed to similar units (see the previous example).
To calculate minimum scans per symbol for this step ladder application, use
the following values:
R = 330 scans/second
H = 1 inch
C = 25 inches/second
330 scans
x
1 inch
=
second
13.2
13.2 scans
25 inches
second
Since S (scans per symbol) is greater than 5 and the application uses good
quality symbols, the 2755-L6SB scanner is appropriate for this step ladder
application.