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F-Guard IR3 HD User Manual
RS-485 Communication Network
Using the RS-485 network capability of the detector and communicator software, it is
possible to connect up to 32 detectors in an addressable system with only 4 wires (2 for
power and 2 for communication). Using repeaters, the number of detectors can be much
larger (32 detectors for each repeater) up to 247 on the same 4 wires. Using the RS-485
network, it is possible to read each detector’s status (fault, alarm) and to initiate a BIT to
each detector individually.
The detector communicates via RS-485 with a Modbus RTU compatible protocol. For
more details on the communication protocol, please see manual F100P0013
Figure 20: RS-485 Networking
Cabling Recommendations
The cable used should be appropriate for the hazardous area classification and meet
local, national and company regulations.
To comply with EMC regulations, the cable must be shielded and the detector grounded.
The use of industrial-grade, suitably armoured field cable is recommended). When using
HART® communications, there are some additional considerations. In particular, a low
capacitance cable should be used. Further detailed information can be found at the
HART® Communication Foundation’s website www.hartcomm.org.
For ethernet cabling, it is recommended to use at least CAT5 shielded.
For analog video cabling, 75 Ohm - analog video patch cable or shielded twisted pair.
Earth/Ground Regime
Any earthing regime employed must avoid earth loops. The following information is
provided to assist with proper earthing of the detector
