Owner's manual

Section
2-1
2 Analog Input (AI)
Function Block
The Analog Input (AI) function block processes field device
measurements and makes them available to other function blocks. The
output value from the AI block is in engineering units and contains a
status indicating the quality of the measurement. The measuring
device may have several measurements or derived values available in
different channels. Use the channel number to define the variable that
the AI block processes.
The AI block supports alarming, signal scaling, signal filtering, signal
status calculation, mode control, and simulation. In Automatic mode,
the block’s output parameter (OUT) reflects the process variable (PV)
value and status. In Manual mode, OUT may be set manually. The
Manual mode is reflected on the output status. A discrete output
(OUT_D) is provided to indicate whether a selected alarm condition is
active. Alarm detection is based on the OUT value and user specified
alarm limits. Figure 2-1 on page 2-5 illustrates the internal components
of the AI function block, and Table 2-1 lists the AI block parameters and
their units of measure, descriptions, and index numbers.
TABLE 2-1. Definitions of Analog Input Function Block System Parameters
Parameter
Index
Number
Units Description
ACK_OPTION 23 None Used to set auto acknowledgment
of alarms.
ALARM_HYS 24 Percent The amount the alarm value must
return within the alarm limit before
the associated active alarm
condition clears.
ALARM_SEL 38 None Used to select the process alarm
conditions that will cause the
OUT_D parameter to be set.
OUT = The block output value and status
OUT_D = Discrete output that signals a selected
alarm condition
OUT_D
AI
OUT
FIELDBUS-FBUS_31A