Vaisala PTU300 - Manual (Page 61)

Chapter 3 ________________________________________________________________ Installation
VAISALA ________________________________________________________________________ 59
1102-028
Figure 33 4-Wire RS-485 Bus
Table 10 4-Wire (Switch 3: On)
RS-485 master Data PTU300
Tx D1+
→
Rx D1+
Tx D0-
→
Rx D0-
Rx D1+
←
Tx D1+
Rx D0-
←
Tx D0-
Stub
Termination Termination
Termination Termination
Twisted pair
120R
120R
120R
120R
Twisted pair
Stub
Stub
Baud > 19.2K Stub < 10ft, 3m
Baud > 112K Stub < 1ft, 0.3m
Rx D0-
Rx D1+
Common
Tx D0-
Tx D1+
Switch
Term off
Term off
2/4 wire on
RS422 off Tx D0-
Tx D1+
Common
Rx D0-
Rx D1+
Switch
Term off
Term off
2/4 wire on
RS422 off Tx D0-
Tx D1+
Common
Rx D0-
Rx D1+
RS485-1
RS485-1
Address MM
Address NN
RS485 bus master
Junction
box
Junction
box
Junction
box
Common
line
Common
line