Vaisala PTU300 Podręcznik Użytkownika Pobierz pdf (Strona 56)

USER'S GUIDE____________________________________________________________________

54 __________________________________________________________________ M210796EN-E

Table 9 Connecting the Twisted Pair Wires to the Screw

Terminals

Screw terminal Data line

(2-wire RS-485)

Data line

(4-wire RS-485/422)

1 (not connected) RxB

2 (not connected) RxA

3 Data pair shield Data pair shield

4 B TxB

5 A TxA

6. If you use RS-485 (or RS-422) 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 RxA and RxB and receives data from PTU300 through

terminals TxA and TxB.

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Vaisala PTU300 Podręcznik Użytkownika Strona 56