Rockwell Automation 1797-Series ControlNet Ex Media Plannng Installation Manual - Manual (Page 28)

Publication CNET-IN003A-EN-P - January 2006
2-6 Plan a ControlNet Ex Media System
For redundant media, decrease the number of taps by half, as shown
in the derating curve.
Figure 2.3 ControlNet Redundant Media Derating Curve
Determine Trunk Cable Section Length When You Use a FLEX Ex
Redundant ControlNet Barrier Module
When you use a FLEX Ex Redundant ControlNet Barrier Module
(catalog no. 1797-BCNR), the total allowable length of a segment
containing standard RG-6 quad-shield cable depends upon the
number of taps in your segment. There is no minimum trunk cable
section length requirement. The maximum allowable length of a
segment that contains a 1797-BCNR module is 500 m. (1640 ft) with
two taps connected. Each additional tap decreases the maximum
length of the segment according to the derating curve. The maximum
number of taps allowed on a segment is 20 with a maximum length of
250 m (820 ft).
EXAMPLE
If your segment requires 3 taps using 1786-RG6
cable, the maximum segment length is:
([20.29 db - 3*.32 db] / 5.99 db] * 304)
(19.33 db / 5.99 db) * 304 = 982 m (3227 ft)
IMPORTANT
The total trunk cable length or number of taps can
be increased by installing a repeater hub on the
segment. This creates another segment.
1000 (3280)
750 (2460)
500 (1640)
250 (820)
2 8 16 24
Maximum Allowable Segment Length
for FLEX Ex on ControlNet =
1000 m (3280 ft) - 16.3 m (53.4 ft) X
[Number of Taps - 2]
Number of Taps
S
eg
m
en
t
Le
ng
th
m
(f
t)
30014-m