IN-E-HyFlex-V4_10
Rotronic AG
Bassersdorf, Switzerland
Document code
Unit
Instruction Manual
Document Type
HygroFlex transmitter version 4: instruction
manual
Document title
Page
59
of 61
© 2006; Rotronic AG IN-E-HyFlex-V2_10.doc
•
direct and alternate current > 400 V
(unshielded)
•
Telephone lines
•
lines leading into EX-rated areas
in separated bundles or channels /
conduits, without minimum distance
Lightning protection
Cabling in areas with a risk of lightning requires a lightning protection. For cabling underground in
between buildings, we recommend the use of special fiber optic cables. If this is not possible, use
copper cables that are suitable for underground installation.
RS-485 Cable
Using a symmetrical transmission method in combination with low capacity/ low attenuation twisted
pair cables, allows extremely reliable long distance connections. The use of a high grade shielded
cable avoids cross talk between the transmitted signals and also reduces the potential of external
interference. For the RS-485 cable, we recommend using a cable Cat. 5e ANSI/ TIA /EIA-568-A-5.
In general the RS-485 cable should be shielded and comply with the following specifications:
-
Cable capacitance
<=300pF/m or 90 pF/ft
-
Line
impedance
100
Ω
±15
Ω
-
Line
resistance
140
Ω
/km or 225
Ω
-
Signal lines
Twisted pair
In addition, we recommend terminating each end of the RS-485 cable with a 240 Ohm resistor.
RS485 Network
Addr. 1
Addr. n
RS485 device connectors
240
Ω
240
Ω
Note: all instruments connected to the network should use the same baud rate
Voltage potential issues
The existence of a voltage-potential between instruments that are interconnected can be a source
on concern in large installations, installations with different mains power supply and in inter-building
networking.
As a first measure, the shield of a signal cable should be connected at both ends. In the case of a
data cable, a low-resistance potential equalization cable may also have to be used. This cable
