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Instruction Manual
IM-106-880C, OI
September 2009
7-23
Hazardous Area OCX 8800
ANALOG INPUT (AI)
FUNCTION BLOCK
Introduction The Hazardous Area OCX 8800 has four transducer block Input/Output
channels (Table 7-20) for the AI function blocks. The status of channel values
are defined in Table 7-22.
The Analog Input (AI) function block (Figure 7-5) 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.
Figure 7-5. 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. Table 7-19 lists the AI block parameters and
their units of measure, descriptions, and index numbers.
OUT = The block output value and status
OUT_D = Discrete output that signalsa selected
alarm condition
OUT_D
AI
OUT
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