Operating Instructions
Chapter
3
CLV 490 Bar Code Scanner
8 009 993/O824/20-12-2004
©
SICK AG · Division Auto Ident · Germany · All rights reserved
3-9
Product description
command strings via the data interface or can be left free running. The CLV either outputs
the reading result at the end of the reading pulse (the back edge of the object has left the
end of reading field) or already during the reading pulse as a result of predefined (parame-
trized) conditions. To separate bar codes of the same type with identical contents, an incre-
mental encoder must be connected to the CLV.
In object polling mode, the CLV automatically detects the beginning and the end of the ob-
ject located in the reading field without any help of external sensors. The minimum temporal
distance between two consecutive objetcs must not fall below 70 ms when the objects are
moved on the conveyor belt.
Tracking mode
During the reading process,
max. 10 objects
can simultaneously be located in the reading
field (following each other) in internal tracking mode, i. e. the CLV must be able to clearly
assign the bar codes to the objects (
). As default, a reading pulse sensor at the be-
ginning of the reading field controls the starting of the reading process. The end of the rea-
ding field is determined by the parametrized object release point in the CLV. In this way, the
size of the reading field is clearly determined.
In order to track the transport of the objects in the reading field, a regularly-timed pulse is
required. This is generated by an external incremental encoder which regularly supplies a
pulse at least every 10 mm (0.39 in) of movement in conveying direction. As a result, the
the distance between the reading pulse sensor and the object release point is clearly time-
mapped in the CLV. Fluctuations when approaching the conveyor or decreases in speed due
to heavy load with numerous conveyor obejcts are also recorded. An internal clock in the
CLV also allows operation at a constant conveyor speed. A gap of at least 50 mm (1.97 in)
is necessary for the clear separation of consecutive objects. The reading result for an object
is output after the back edge of the object passes the object release point. Alternatively, the
reading process can be started with a command strings via the data interface.
Fig. 3-5:
Reading modes of the CLV in stand-alone configuration
3.2.4
Scan procedure variants
Line scanner (standard device)
Generates a scan line; due to the V-principle of the beam generation, the reading field height
(the useful length of the scan line for evaluation purposes) is dependent on the reading
distance.
Start/stop mode
Tracking mode
