ROTRONIC HF8 - Manual (Page 15)

E-M-HF8-V2_10
Rotronic AG
Bassersdorf, Switzerland
Document code Unit
HygroFlex HF8 Humidity Temperature
Transmitter: User Guide Instruction Manual
Document Type
Page 15 of 35
Document title
© 2012; Rotronic AG E-M-HF8-V2_10
•
direct and alternate current > 400 V
(unshielded)
•
Telephone lines
•
lines leading into EX-rated areas
in separated bundles or channels /
conduits, without minimum distance
Lightning protection
Cabling in areas with a risk of lightning requires a lightning protection. For cabling underground in between
buildings, we recommend the use of special fiber optic cables. If this is not possible, use copper cables that
are suitable for underground installation.
6.2 Guidelines for RS-485 wiring
See document E-DV04-RS485.01: RS485 Network Installation and Start-up Guidelines
6.3 Cable grip and cable specifications
The HF8 is supplied either with one M16 sealing cable grip or with a ½” conduit adapter. The M16 cable grip
provides effective sealing only with cables having the proper outside diameter. Preferably, use a cable with an
outside diameter of 6 to 7 mm (0.236 to 0.275 inch) with 18 AWG wires.
6.4 Wiring
6.4.1 Electrical diagrams
Note: the following diagrams apply to the HF8 with any of the galvanically isolated power supply options.
HF8 analog voltage outputs
The maximum permissible cable length can be determined under consideration of the voltage drop caused by
the current flowing to the devices connected to the unit. The voltage drop in the cable depends both on cable
resistance and on the equivalent resistance of the devices connected in parallel to the unit. The total
resistance connected to each unit output should be at least 1000 ohms. Cable resistance should not be more
than 1/1000 of the load resistance.