ABB Symphony Harmony Series, Instruction, Page: 133 / 402

3 - 4 WBPEEUI240751C0
Inputs and Outputs
Readback
Each analog output channel is monitored on the block. This
readback function serves two purposes:
•
Provides high accuracy by using a software compensation
algorithm in combination with the analog output readback
value.
•
The integrity of the hardware and field wiring is constantly
monitored by way of checking the readback value.
The block also reports the readback values to the controller. It
automatically scales the values to their proper engineering
units before reporting them. The readback values are con-
verted to the proper engineering units based on engineering
unit high and low value specifications.
Digital Input
Digital input channels can be used to read the states of
switches, relay contacts, and solenoids (Fig.
3-3 ). The following
digital inputs are supported:
•
24, 48, and 125 VDC.
•
120 and 240 VAC.
Figure 3-3. Digital Input
T 00 55 6 A
EX T ER N A L F IEL D
PO W ER E D
(SW IT C H H OT )
EX T ER N A L F IEL D
PO W ER E D
(SW IT C H C O M M O N )
IN T ER N AL F IE LD
PO W ER E D
+
+
+
–
–
–
C O M M O N
C O M M O N
V
S O U R C E
V
S O U R C E