Vaisala HMT130 - Manual (Page 27)

Chapter 3 ________________________________________________________________ Installation
VAISALA ________________________________________________________________________ 25
Table 3 Wiring Table
Terminal Description
1 SGND (signal ground)
2 CH1+ (signal +)
3 CH2+ (signal +)
4 Cable shield (optional)
5 Vin- (power supply - or VAC)
6 Vin+ (power supply + or VAC)
7 485-
8 485+
9 GND (ground)
10 Relay
11 Relay
Numbers 1 ... 6 in the first column of the wiring table refer to section (A)
and numbers 7 ... 11 to section (B) in Figure 12 on page 24.
There is an internal connection between numbers 1 and 5 on section (A)
and number 9 on section (B).
RS-485 Bus Termination
If you use RS-485 to connect just one HMT130 to a master computer,
enable the internal termination of HMT130 by switching switches 1 and
2 ON. Make sure that the master's end of the line is also terminated (by
using master's internal termination or with a separate terminator).
If you are connecting many transmitters to the same RS-485 bus, make
sure that switches 1 and 2 are OFF and terminate the bus with separate
terminators at both ends. This allows removing any transmitter without
blocking the bus operation.