User`s guide

Chapter 4 ________________________________________________________________ Installation
RS485 for COM2 with Cable 2 m and 10 m
In RS485 mode, the same signals as in RS422 mode are available
at the end of Cable 2 m and Cable 10 m. Make two-wire loop-
backs at the end of the cable, as shown in Table 23 and Figure 35
below.
Table 23 COM2 RS485 Wiring
WMT700 Signals
Wire Colors
Pin
RS485 Signals
RxB
Green
3
-
TxB
Yellow
4
TxA
Brown-Green
14
+
RxA
White-Yellow
15
1009-016
Figure 35 COM2 RS485 Wiring
NOTE
To avoid confusion, the RS485 and RS422 signals of
WMT700 are
named as follows:
-
Inverting: –
-
Non-inverting: +
According to the EIA
-485 standard, the lines are named as follows:
-
Inverting: – <=> A
-
Non-inverting: + <=> B
The A/B naming used by some manufacturers is in conflict with the
standard. To ensure proper operation, verify the polarity of the signals
when using the device on the bus with signals named as A/B. Opposite
polarity causes data inversion on the bus, but it does not damage the
device.
VAISALA ________________________________________________________________________ 79