Rockwell Automation 2755 Atomscan Bar Code Scanner - Manual (Page 19)

Chapter 3
Designing the System
3–8
Determining the Read Range
The Read Range is the distance from the face of the scanner over which a bar
code symbol can be read reliably. Read Range varies with:
•
the bar code symbol’s Narrow Element width
•
bar code symbol quality, including print contrast
In picket fence applications the scanner and symbol are usually set as far
apart as possible within the Read Range, to give the greatest number of scans
per symbol.
Table 3.A
Read Ranges
Scanner (Apparent) Narrow
Element Width
Nearest and Farthest Distances
from Scanner (Read Range)
mils millimeters inches centimeters
2755-L6SB and
2755-L6RB 7.5
10
20
30
40
50
.19
.25
.51
.76
1.0
1.3
2.5 - 6
2.0 - 7
2.0 - 9
3.0 -10
4.0 -10
5.0 -10
6.4 - 15.2
5.1 - 17.8
5.1 -22.9
7.6 - 25.4
10.2 - 25.4
12.7 - 25.4
2755-L6SA and
2755-L6RA 5.0
7.5
.13
.19 2.0 - 3
1.0 - 4.5
5.1 - 7.6
2.5 -11.4
Useable Scan Width
The useable scan width is the distance across the scan beam in which a given
symbol can be read reliably. A larger scan width will give:
•
more time in which a moving symbol can be read by the scanner, and/or
•
more scans that can be made per symbol
Table 3.B
Useable Scan Width
Distance from the Scanner Useable Scan Width
inches centimeters inches centimeters
1
2
3
4
5
6
7
8
9
10
2.5
5.1
7.6
10.2
12.7
15.2
17.8
20.3
22.9
25.4
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5
3.8
6.4
8.9
11.4
14.0
16.5
19.0
21.6
24.1
26.7