Cabling Recommendations; Earth/Ground Regime; Figure 20: Rs-485 Networking - GasTech F-Guard-IR3-H2 User Manual

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

Cabling Recommendations

The cable used should be appropriate for the hazardous area classification and meet local,
national and company regulations.
In order to comply to EMC regulations, the cable must be shielded and the detector grounded.
The use of industrial grade, suitably armored field cable is recommended. When using HART®
communications, there are some additional considerations. In particular, low capacitance cable
should be used. Further detailed information can be found at the HART® Communication
Foundation's website www.hartcomm.org .

Earth/Ground Regime

Any earthing regime employed must avoid earth loops. The following information is provided to
assist with proper earthing of the detector
• There is an earthing point on the outside of the detector enclosure for connection to
Electrical ground
2.12.1 General recommendations
In general, correctly engineered star earthing arrangements minimize earth current
•
crosstalk and noise, improving the reliability and performance of instrumentation.
The use of a single, screened / shielded cable for each field device ensures good
•
screening / shielding and reduces crosstalk.
For more information & technical support:
F-Guard IR3-H2 User Manual

Figure 20: RS-485 Networking

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