Vaisala PTU300 - Manual (Page 60)

User's Guide _______________________________________________________________________
58 ___________________________________________________________________ M210796EN-G
Installation and Wiring
1. Disconnect the power. In case the RS-422/485 module is installed
in the factory, continue with the item 4.
2. To attach the module, open the transmitter cover and fasten the
RS-422/485 module to the bottom of the housing with four screws.
3. Connect the flat cable between the RS-422/485 module and the
motherboard's pins MODULE1 (Communications).
4. Pull the network wirings through the cable gland.
5. Connect the twisted pair wires (1 or 2 pairs) to the screw terminals
as presented in Table 9 below:
Table 9 Connecting the Twisted Pair Wires to the Screw
Terminals
Screw Terminal Data Line
(2-wire RS-485) Data Line
(4-wire RS-422/485)
1 (not connected) Rx D0-
2 (not connected) Rx D1+
3 Common Common
4 D0- Tx D0-
5 D1+ Tx D1+
To avoid problems in the RS-422/485 network, the Common
terminal should be wired to the corresponding terminals of the
other devices.
6. If you use RS-422 or RS-485 to connect just one PTU300 to a
master computer, enable the internal termination of PTU300 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.
NOTE If you use the internal termination of the transmitter at the end of the RS-
485 bus (instead of using separate terminators) removing that transmitter
will block the bus operation.
7. Use the bus type (4-wire/2-wire) to select the selection switch 3.
In 4-wire mode RS-485 master sends data to the PTU300 through
terminals Rx D1+ and Rx D0- and receives data from PTU300
through terminals Tx D1+ and Tx D0-.