Vaisala LT31 - Figure 37 RS-485 Communication Option

User's Guide ______________________________________________________________________
80 __________________________________________________________________ M210667EN-C
RS-485
Remote computer
RS-485
transceiver
Other system
RS-485
receiver
Driver
+
-
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
13
14
15
16
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
0401-159
Figure 37 RS-485 Communication Option
Terminate the RS-485 chain with a 120  resistor. This is especially
important with long cables. If LT31 is at the end of the RS-485 chain, the
120  resistor can be connected across the screw terminal pins. The
120  resistors are available in a plastic bag inside the interface
enclosure.