Owner's manual

Additional Installation Tips
6.7 CableandBusTerminationRS485
• If maximum transfer distan ce and maximum transfer speed is needed,
shielded and twisted pair cable should be used. The mutual capacitance
may not exceed 52.5 pF/m, and the cable area should be at least 0.25 mm
2
(AWG 24).
• 0 V, the reference voltage for c ommunication should be included in
the cabling. With two-way communication use two pairs; one pair for
communication and one pair for 0 V.
• The shield mus t be grounded at one end. The other end is usually grounded,
but with longer distances or when there is a difference in the ground potential,
theshieldshouldbeconnectedtothegroundvia0.1μF/250Vplastic
capacitor to prevent ground current in the braided shield. A number of
manufacturers recommend that the shield be grounded at each node. Various
manufacturers have different systems for bus termination.
Depending on the recipients’ design, the bus wires may be on the same level or
require pull-up or pull-down to ensure that no faulty signals are detected w hen the
bus is in resting mode (all transmitters are disconnected).
BeijerElectronics, MAEN096C
25