Vaisala HMW90 - Manual (Page 35)

Chapter 3 ________________________________________________________________ Installation
VAISALA ________________________________________________________________________ 33
Wiring HMW95
The RS-485 line of the transmitter is isolated from the power supply. A
separate ground reference terminal (GND) is provided for the RS-485
connection.
If you are using a shielded cable, you can use the Shld terminal to hold
the exposed part of the shield. Note that the Shld terminal is floating
(not electrically connected).
1209-014
Figure 20 Wiring HMW95
Connecting Several Transmitters on Same RS-485
Line (HMW95)
Set the RS-485 termination jumper to “ON” on the transmitter that is at
the end of the line. This terminates the line with a 120 Ω resistor. For
location of the jumper, see section Transmitter Parts - Inside on page 6.
Connect the cable shield to ground on the building controller side.
1209-015
Figure 21 Several Transmitters on Same RS-485 Line
D- -Vs D+ +Vs
+
-
Power supply
18 ... 35 VDC
or 24 VAC ±20%
RS-485
Shld GND
Transmitter
D-
-Vs
D+
+Vs
Shld
GND
Building controller Transmitter Transmitter
Power
supply
D-
D+
+Vs
-Vs
GND
SHIELD
RS-485:
BACnet or
MODBUS
master
Connect shield on controller side
Set RS-485
termination jumper
D-
-Vs
D+
+Vs
Shld
GND
D-
-Vs
D+
+Vs
Shld
GND