Microscan MS-890 User Manual page 292

Formulas for Number of Decodes
Raster Picket Fence Calculation
For raster picket fence scanning, the number of decodes
(ND) that can be applied to a given symbol can be calculated
once the sweep rate (SPS) is known.
Sweep Rate (Sweeps per Second)
Sweep rate is the number of raster sweeps (up or down) that
occur per second and can be set in ESP. Since the sweep
rate cannot exceed 30, you first need to ensure that your
application can achieve this by solving for sweep rate (SPS).
The sweep rate should generally be set as low as possible in
order to maximize the number of scans on a given symbol.
The formula for finding Sweep Rate (SPS) is as follows:
SPS = Sweeps per Second, the number of passes, up or down, that are described by the
arc of the raster mirror.
SS = Symbol Speed, the inches per second that a symbol moves through the scan.
SW = Scan Width, the width across the scan beam, at a given distance from the scanner,
in which a symbol can be read (picket fence formula only).
SL = Symbol Length, the length of the longest printed symbol to be read plus the length of
the quiet zones (picket fence formula only).
Example:
Important: The maximum sweep rate that your can set the scanner to is 30. If your solution
is greater than 30, you must change another parameter such as symbol speed, etc., and
recalculate.
Since SPS can only be entered into the software as whole numbers, round off fractions of
SPS to the next higher number, for example enter 0.4 as 1 and 3.5 as 4.
In setting up the scanner, raster height depends on the raster arc and the symbol distance
(range) from the scanner. Both the top offset and bottom offsets can be adjusted independently
in 255 increments and the resulting arc can vary from 0° to 30°. (See Chapter 10, Raster/Laser.)
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MS-890 Industrial Automation Scanner User Manual
Raster Picket Fence
Orientation