ROTRONIC HF3 - Manual (Page 13)

E-M-HF3-V1_22
Rotronic AG
Bassersdorf, Switzerland
Document code Unit
HygroFlex HF3 Transmitters and Thermo-
hygrostats: User Guide Instruction Manual
Document Type
Page 13 of 27
Document title
© 2009-2011; Rotronic AG E-M-HF3-V1_22
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 Cable grip and cable specifications
Both type D and type W have one M16 sealing cable grip. This 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.
6.3 Wiring
6.3.1 HF32: 2-wire, loop powered transmitter
Electrical diagram
The maximum permissible cable length
connecting the HF32 to other devices is
determined by the total resistance resulting
from the addition of the cable resistance and
that of the devices connected in series with
the unit. This resistance should not exceed
500 ohms.