Vaisala LT31 - Figure 36 RS-232 Communication Option; Serial Multipoint Transmission with RS-485

Chapter 4 _______________________________________________________________ Installation
VAISALA _______________________________________________________________________ 79
RXD
TXD
GND
MOD1
MOD2
MOD3
MOD4
MOD5
20
21
22
23
24
25
26
27
Module
(modem)
(modem)
Maint.
line
RS-232
RS-485+
RS-485-
18
19
Data
line
CTS
RTS
RXD
TXD
GND
RTS
PC
RTS
2
D-9 pin
7
3
8
5
13
CTS
CTS
14
TXD
TXD
15
RXD
RXD
16
GND
GND
RS-232
Communication
line
17
Data
line
RS-232
VB+
VB-
RS-485+
RS-485-
9
10
11
12
Sensor
line
+12V Out
GND
5
6
7
8
1
2
3
4
Reset
Status
RXD
TXD
Reset Button
0401-055
Figure 36 RS-232 Communication Option
Serial Multipoint Transmission with RS-485
The RS-485 transmission standard allows several LT31s to communicate
(half-duplex) with the host computer using a single twisted pair. The RS-
485 interface is potential separated. For the RS-485 communication
method, connect the signal wires to the screw terminal at the CPU board.
See Figure 37 on page 80.
NOTE
The cable shield of RS-485 cable must be properly grounded in the
cable gland of interface enclosure, see Figure 35 on page 77.