Vaisala DRYCAP DMT346 Betriebsanweisung PDF herunterladen (Seite 51)

Chapter 3 ________________________________________________________________ Installation

VAISALA________________________________________________________________________ 49

Table 6 Connecting Twisted Pair Wires to 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 DMT346 to a

master computer, enable the internal termination of DMT346 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 DMT346

through terminals RxA and RxB and receives data from

DMT346 through terminals TxA and TxB.

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Vaisala DRYCAP DMT346 Betriebsanweisung Seite 51