AUMA SA 25.1 Operating Instructions Manual page 25

SA 25.1 SA 48.1/SAR 25.1
AC 01.2 Non-Intrusive Modbus RTU
Fieldbus cable
SAR 30.1 Control unit: electronic (MWG)
The interference immunity of signal and fieldbus cables increases if the cables
are laid close to the earth potential.
If possible, avoid laying long cables and make sure that they are installed in
areas being subject to low interference.
Avoid parallel paths with little cable distance of cables being either susceptible
to interference or interference sources.
Table 12:
Cable recommendation
Only cables complying with the recommendations of EIA 485 specifications should be used for Modbus
wiring.
Impedance
Cable capacity
Wire diameter
Cross section
Loop resistance
Screening
Prior to installation, please note:
Connect maximum 32 devices to one segment.
If more devices are to be connected:
- Connect several segments using repeaters.
Install fieldbus cables at a distance of minimum 20 cm to other cables.
If possible, fieldbus cables should be laid in a separate, conductive, and earthed
cable tray.
Ensure absence of equipotential earth bonding differences between the indi-
vidual devices at fieldbus (perform an equipotential earth bonding).
Table 13: Transmission rate/cable length for line topology
Baud rate (kbit/s) Max. cable length (segment length)
without repeater
9.6 115.2 1,200 m
Table 14: Transmission rate/cable length for loop topology
Baud rate (kbit/s) Max. cable length between actuators
(without repeater)
9.6 115.2 1,200 m
135 to 165 Ohm, at a measurement frequency between 3 and 20 MHz
< 30 pF per metre
> 0.64 mm
> 0.34 mm², corresponds to AWG 22
< 110 Ohm per km
CU shielding braid or shielding braid and shielding foil
Electrical connection
Possible cable length with repeater
(total network cable length)
Approx. 10 km
Max. possible cable length of redund-
ant loop
Approx. 290 km
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