Chapter 3 _______________________________________________________________ Installation
VAISALA_______________________________________________________________________ 61
Termination
Termination Junction box
Junction box
Junction box
120R
D0-
D1+
Common
Switch
Term off
Term off
2/4 wire off
RS422 off
Stub
Stub
Stub
RS485-1
RS485-1
RS485 bus master
Twisted pair
Address NN
Address MM
Common
D0-
D1+
Switch
Term off
Term off
2/4wireoff
RS422 off
Common
D0-
D1+
5
4
3
2
1
5
4
3
2
1
120R
1102-027
Figure 38 2-Wire RS-485 Bus
Table 8 2-Wire (Switch 3: Off)
RS-485 master Data HMT330
D1+ ↔ D1+
D0- ↔ D0-
8. When operating in communication mode RS-422, set both switches
3 and 4 to ON position (4-wire wiring is required for RS-422
mode).
9. Connect the power and close the cover.
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