WaveStar Color Monitor_____________________________________________________________
Ctrl Nr: PM375103 Revision: 003
12
•
Run a dedicated ground wire with the signal wires and only ground the shield at one end.
2.3
Modbus RTU Cables
2.3.1
Cable Specification
RS485/RS422 cable length can be up to 4000 ft. if you use the proper cable:
•
The cable resistance should be ≤ 27 ohms/1000ft @ 1 kHz and the mutual capacitance
should be ≤ 14pf/ft @ 1 kHz.
•
4-wire cabling:
o
RS422 is typically 4-wire.
o
Use a shielded cable with two (2) twisted pairs and a shield/ground wire.
o
The two transmit lines must be in one twisted pair and the two receive lines in the
other twisted pair.
•
2-wire cabling:
o
RS485 is typically 2-wire and is slower than RS422.
o
Use a shielded cable with one (1) twisted pair and a shield/ground wire.
2.3.2
Cable Biasing and Termination
PDI devices have soft biasing (27K pull-up and pull-down resistors) on the + and
– transmit and
receive lines. Therefore, if the customer’s Master device allows for control, PDI recommends that the
user turn on biasing and turn off termination
, which may “fight” the biasing. Biasing the Master
device’s lines is not critical because the Color Monitor is already biasing the lines. If termination is
needed because of an extremely long cable run, PDI recommends that a small capacitor be put in
series with the terminating resistor.
2.4
Ethernet Cables
The maximum length of Ethernet cable depends upon the customer’s choice of Ethernet cable.
2.5
Customer Modbus RTU Connections
When a Color Monitor is embedded in a PDI product (PDU, RPP, or JCOMM), the customer does not
typically wire Modbus RTU directly to the Monitor. Downstream Modbus RTU links are typically to
internal devices and are wired at the factory. The upstream Modbus RTU link is extended from the
Monitor to a customer connection port, which differs by unit.
Color
Monitor
or BMS
Devices 2/3
BCMS PCB
Subfeeds
Devices 4/5
BCMS
Panelboards
Device 1
PDU Board
RX+
TX+
TX+
TX+
RX-
TX-
TX-
TX-
TX+
RX+
RX+
RX+
TX-
RX-
RX-
RX-
Figure 5 Color Monitor 4-wire Modbus Connections
