User Manual

E-M-HF4-V1_22
Rotronic AG
Bassersdorf, Switzerland
Document code
Unit
HygroFlex HF4 Humidity Temperature
Transmitters: User Guide
Instruction Manual
Document Type
Page
16 of 29
Document title
© 2009-2011; Rotronic AG E-M-HF4-V1_22
Measuring humidity or temperature only
Unless configured to measure either humidity only or temperature only, proper operation of the HF42 requires
both current loops to be closed. The HF42 can be directly ordered from the factory to measure either humidity
or temperature only. When necessary, any unused output of the HF42 can be disabled with the ROTRONIC
HW4 software. When the HF42 is configured with one of the two outputs disabled, close only the loop that is
being used.
6.4.2 HF43: 3-wire transmitter
Electrical diagram for 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.
Minimum load requirements apply to the external device or circuit connected to the HF4 transmitter. These
requirements are defined in the “Operation” chapter
Electrical diagram for current outputs
The maximum permissible cable length, connecting
the unit 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.