Specifications

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Appendix B—Connecting to a Network
This section describes setting up a network with multiple Power Patrol instruments using the BACnet or
Modbus communication protocol. A network can support up to 127 Power Patrol instruments using the
BACnet protocol and 247 Power Patrol instruments using the Modbus protocol.
COMMUNICATION PROTOCOL
BACnet MS/TP and Modbus RTU are standard communication protocols that allow for communication
between a client and multiple devices connected to the same network. RS-485 is the protocol standard
used by Power Patrol meters as the hardware’s serial interface while BACnet or Modbus is the
communication protocol.
DAISY CHAIN LAYOUT FOR RS-485 NETWORK
When multiple devices are connected the devices need to be connected in a daisy chain. A daisy chain
means that all plus (+) connections are chained together and all minus (-) connections are chained
together across the network.
A network containing multiple devices requires a unique address for each device. This allows the master
device to identify and communicate with each slave. The BACnet/Modbus network administrator must
assign a unique network address to each Power Patrol using the rotary switches SW1-SW2.
Other network layouts are not recommended when using the RS-485 standard.
NETWORKING USING THE BACNET/MODBUS PROTOCOL
1) Install the BACnet/Modbus cable.
2) Set a unique address for each device using the table in Appendix C.