Microscan MS-890 User Manual page 291

Appendix K — Formulas for Number of Decodes
To ensure reliable scanning, apply a minimum of five decodes to each symbol. Use the
formulas below to calculate 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 minimum
for your application, 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
Ladder scanning is seldom done with raster scanning unless
the raster is set for single scan line scanning (Top Offset
setting equal to Bottom Offset) or symbols are presented
as stop-and-go.
For single scan line ladder scanning, use the following formula:
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.
Example:
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-890 Industrial Automation Scanner User Manual
Appendices
1
Single Line Ladder
Orientation
A-27