Operating Instructions
Chapter
6
CLV 490 Bar Code Scanner
8 009 993/O824/20-12-2004
©
SICK AG · Division Auto Ident · Germany · All rights reserved
6-27
Operation
Explanation
Object polling
The process of setting up this automatic reading pulse control (object detection space, scan
angle, and oscillating angle limitation) is not the same as that for defining the focus control
(reading space and autofocus area) and has to be performed separately. The object
detection space should include the rectangular autofocus space.
Object polling begins once the system has been started. To prevent incorrect triggering, the
system does not return to reading mode from a different operating function or terminate a
diagnosis function until a 5 second delay has elapsed.
The CLV can carry out object polling in autofocus mode with the "Minimum distance" and
"Differential background" modes. The periodic distance measurement is also used for
object detection in the parameterizable search interval. The autofocus, however, is only
active during the reading gate. To ensure reliable object detection, the CLV must detect an
object of the defined minimum width within a preset time in every distance profile (line
scanner with oscillating mirror: in at least 3 distance profiles over at least 500 ms). This time
is used to debounce the object detection prior to automatic starting of the internal reading
gate. Only
one object
should be in the reading field at any one time.
Blanking: the smallest parameterizable object width required for an object to be detected
and the reading gate to be started is 100 mm (3.94 in). The minimum object width when
the object leaves the reading field (end of reading gate) is 50 mm (1.97 in) (fixed). The
object width here is not dependent on the distance between the object and the CLV. After
an active reading gate, the pause interval must be at least 70 ms. If the parameterized
pause interval is any shorter, the CLV searches for objects continuously with its laser diode
permanently switched on. This reduces the service life of the laser diode. In this pulse mode,
the oscillating mirror can oscillate permanently or only during the active reading gate.