ROTRONIC HF8 - Manual (Page 19)

E-M-HF8-V2_10
Rotronic AG
Bassersdorf, Switzerland
Document code Unit
HygroFlex HF8 Humidity Temperature
Transmitter: User Guide Instruction Manual
Document Type
Page 19 of 35
Document title
© 2012; Rotronic AG E-M-HF8-V2_10
6.4.3 Power ground and analog signal ground
Depending on the power supply option, the negative side of the analog output signals is either tied to or
isolated from the negative of the power supply (VDC) or the neutral (VAC). Please see 3.1 for more details.
Note: the protective ground (terminal block K6) is not tied to the negative of the power supply (VDC) or the
neutral (VAC).
6.4.4 Grounding
We generally recommend grounding the (-) side of the power supply, especially if the electronics will be
subjected to a low humidity environment (35 %RH or less).
6.4.5 RS-485 wiring example with power via main data line
In the following example, one HF8 is the RS-485 master and is connected to an Ethernet network. The other
HF8 transmitters are RS-485 slaves. All units are connected to the RS-485 data cable using a T junction box
AC3021. Power is centrally supplied to all units via the RS-485 data cable from a single DC voltage source.
Terminal Block K8 (Relay 2) Description
K8-1: NC Normally closed (relay not energized)
K8-2: COM Common
K8-3: NO Normally open (relay not energized)
NOTE: this example does not apply to
models with any of the galvanically
isolated power supply options