For those applications requiring accurate line speed detection an external
encoder is needed.
The external encoder will provide accurate signals eliminating problems in
those applications where moving product has an acceleration or deceleration
component in its motion. Selecting the external encoder should take into
consideration a supply source that will yield the correct aspect ration of printed
height to width.
A vertical printed column contains 12 dots and spans 1/8”. This equates to
0.0104 between each vertical dot placement, thusly each horizontal dot
placement should be the same to maintain a perfect 96 DPI ratio.
Selecting the external encoder, the line speed calculation is replaced by a
scalable encoder setting ranging from 0-7 allowing a printed message to be
compressed or expanded. Ideally, the external encoder should be provided to
use this feature to its maximum advantage.
If the external encoder were selected to provide a resolution of 0.0104
then the external encoder set to 0 would produce the correct aspect ratio and the
message can only be expanded in multiples of 0.0104 thousands of an inch. This
may provide all that is required. Selecting an external encoder source that
provided 0.005 thousands of an inch would be a better choice.
The above pictorial is an example of the connections for an external
encoder.
If it becomes necessary to supply both external product detect, and
external encoder, both signals can be wired into the same connector, or DIGITAL
DESIGN INC can supply an optional adaptor to allow connection of both cables
(part number C21012)
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EVOLUTION SC
SYSTEM MANUAL Issue 1.1 15 November 2006
