Appendix J Formulas For Number Of Decodes; Figure A-6 Ladder - Microscan MS-710 User Manual

Appendix J — Formulas for Number of Decodes
To ensure reliable scanning, the scanner should apply a minimum of five scans to each
symbol. Use the formulas below to predict the number of decodes that your symbol will
receive.
If the number of decodes you derive from one of these calculations is less than the min-
imum, plug in the minimum number of decodes (5) and solve for another parameter
that might be changed such as symbol speed or scans per second.
Note: While the formulas given here solve for the predicted number of decodes, you
may also use the formulas to solve for other parameters that might be changed, such
as symbol speed, symbol length, etc.
Single Line Ladder Calculation
For single scan line ladder scanning, use the following for-
1
mula:
 
SH
×
------- -
ND = DR – 3
 
SS
Example:
SH = 1 inch
SS = 10 inches per second
SR = 500 scans per second
 
1
×
----- -
500 – 3 = 47 complete scans
 
10
ND (Number of Decodes) is the number of decodes that a given symbol can be expected
to achieve in a given application.
SH (Symbol Height) is a measurement of the height of individual bars.
SS (Symbol Speed) is the distance per second that a symbol moves through the scan.
DR (Decode Rate) is the number of scans per second that a given symbol receives.
1. The -3 component in the formula is included to allow for AGC acquisition, an incomplete first
scan, and an incomplete last scan. This applies only if the number inside the parentheses equals
4 or more. If the number equals 3, then only subtract 2 to derive 1 good scan.
MS-710 Scanner User's Manual
A-24
Direction of label travel
Scan Line

Figure A-6 Ladder