Rockwell Automation 1760-xxxx Pico GFX-70 Controllers User Manual - Manual (Page 70)

Publication 1760-UM002B-EN-P - March 2005
2-36 Installation
Calculating Cross-Section with Known Cable Lengths
The minimum cross-section is determined for the known maximum extent of
the network.
l = cable length in m
S
min
= minimum cable cross-section in mm 2
ρ
cu
= resistivity of copper, if not otherwise stated 0.018
Ω
mm
2
/m
Calculating Length with Known Cable Cross-Section
The maximum cable lengths are calculated for a known conductor
cross-section.
l
max
= cable length in m
S = minimum cable cross-section in mm
2
ρ
cu
= resistivity of copper, if not otherwise stated 0.018
Ω
mm
2
/m
Plugging and Unplugging Network Cables
Pico GFX-70 is provided with two RJ45 network sockets.
The socket 1 in the first station is for the bus terminating resistor. For other
stations, socket 1 is used for plugging in the incoming cable. Socket 2 is used
for the outgoing cable or for the bus termination resistor on the last physical
station in the network.
S
min
= l x
ρ
cu
12.4
IMPORTANT
If the result of the calculation does not yield a standard
cross-section, the next larger cross-section is used.
l
max
= S x 12.4
ρ
cu