Figure 8-4: AI Function Block
OUT = The block output value and status
OUT_D = Discrete output that signals a selected alarm condition
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 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, you can set OUT 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. Table 8-19 lists the AI block parameters and their units of measure,
descriptions, and index numbers.
Table 8-19: Definitions of AI Function Block System Parameters
Parameter Index number Units Description
ACK_OPTION 23 None Used to set auto
acknowledgement of
alarms.
ALARM_HYS 24 Percent The amount the alarm
value must return within
the alarm limit before the
associated active alarm
condition clears.
Manual FOUNDATION
™
Fieldbus
00809-0500-4880 December 2022
Rosemount OCX8800A 147
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