Chapter
10
Operating Instructions
CLV 490 Bar Code Scanner
10-58
©
SICK AG · Division Auto Ident · Germany · All rights reserved
8 009 993/O824/20-12-2004
Appendix
10.8.3
Calculating the necessary bar code distance if several bar codes are read on
each object
Fig. 10-43: Required distance between the bar codes on an object
A
B
C
D
E
A
B
C
D
E
A
B
C
D
E
A
B
C
D
E
dx
dx
dy
SMART Decoder:
for bar codes with identical code type and identical or different data contents.
Distance dx:
min. 60 x module width
e. g. 30 mm for module width 0.5 mm (19.7 mil)
Distance dy:
7 x d
scan
where d
scan
= vertical distance between two consecutive scan lines
e. g. scan line 90 to bar code, scanning frequency 800 Hz, v = 2 m/s
V
2000 mm/s
dscan = ----
dscan = -------------------- = 2.5
f
800 /s
dy = 7 x 2.5 mm = 17.5 mm (0.7 in)
Standard Decoder:
The above distances are also required for reading bar codes with identical names (identical
data content and code types).
Prerequisite for separating bar codes with identical names:
1. The C
ODE
DISTANCE
between the bar codes must be parameterized correctly
(D
EVICE
CONFIGURATION
tab,
TRACKING
PARAMETERS
button)
2. The code position comparison must be activated
(C
ODE
CONFIGURATION
tab, C
ODE
POSITION
section)
Bar code lines in conveyor direction:
If the scan line is to detect bar codes of the same name with the same code position, the travel
information must be supplied by an external incremental encoder or the internal INC timer so
that the bar codes can be distinguished from one another.
Rule of thumb: the blank zone should surround the bar code completely!
C
ODE
C
ONFIGURATION
tab: due to the function O
PTIMIZE
FOR
SHORT
CODE
DISTANCES
under SMART-
P
ARAMETER
smaller code distances as described above are possible (depending on application)
