DESCRIPTION AND OPERATION
PHYSICAL OPERATION
2 - 2
Figure 2-1. Analog Point-to-Point Communications Wiring
Figure 2-2. ABB Digital Field Bus and HART Wiring
T 0 1 3 2 3 B
S T T
+
–
–
–
+
+
C O M M U N IC AT IO N S A R E
N O T P O S S IB L E O N T H IS
S ID E O F 2 5 0- R E S IS TO R
Ω
C O M M U N IC AT IO N S A R E
P O S S IB L E O N T H IS S ID E
O F 2 5 0 - R E S IS TO R
Ω
S IG N A L W IR E S
F IE L D D E V IC E
U P TO 1 M I. (1 .6 K M )
S Y S T E M P O W E R
S U P P LY
P W R /
O U T P U T
C O N T R O L L E R ,
R E C O R D E R O R
C O N T R O L S Y S T E M
2 50
Ω
T 0 1 3 2 4 B
S T T
S IG N A L W IR E S
T E R M IN AT IO N
U N IT
F IE L D B U S
I/O M O D U L E
M F P /M F C
–
–
+
+
F IE L D D E V IC E 1
F IE L D D E V IC E 8
P W R /
O U T P U T
P W R /
O U T P U T
