ROTRONIC HF8 - Manual (Page 5)

E-M-HF8-V2_10
Rotronic AG
Bassersdorf, Switzerland
Document code Unit
HygroFlex HF8 Humidity Temperature
Transmitter: User Guide Instruction Manual
Document Type
Page 5 of 35
Document title
© 2012; Rotronic AG E-M-HF8-V2_10
c) Option 3: 85 to 265 VAC, 5 Watt, 50-60 Hz, galvanically isolated
As with option 2, the HF8 is equipped with an internal power module that provides galvanic isolation
between power and the analog signals. As a result, the negative (or ground) side of the analog output
signals is not tied with the negative side (VDC) or neutral (VAC) of the power supply.
d) Option 4: power over a RS-485 network
With the exception of models with any of the galvanically isolated power supply options, the HF8 with RS-
485 interface can be directly powered from the main RS-485 data line. In that case the power terminals of
the HF8 should not be connected.
e) Option 5: power over Ethernet (PoE)
The HF8 is available in a special 100% digital version (Ethernet interface only) that allows power over
Ethernet (IEEE 802.3af compliant)
See Technical Data > Specifications for the typical current consumption of the HF8
3.2 Probe inputs
The HF8 has two probe inputs. Probe input 1 is the input that is
the closest to the front of the transmitter.
Using the ROTRONIC HW4 software (Device Manager), each probe input can be configured to accept one of
the following:
o HygroClip 2 humidity-temperature digital probe.
o 1-channel analog probe (general): To be compatible with the HF8 the analog probe must meet the
following requirements: supply voltage: max. 5 VDC, current consumption: max. 10 mA, output signal: 0
to max. 3.3 VDC. The HF8 uses a 12-bit A/D converter to digitize the probe analog signal and can be
configured to measure practically any parameter.
o Analog pressure probe: this is a special case of analog probe and is subject to the same compatibility
requirements. When analog pressure probe is selected, the HF8 automatically uses the signal from the
probe to calculate any humidity parameter that requires barometric pressure as an input value (example:
mixing ratio).