
104
Reference Manual
00809-0100-4697, Rev GA
Appendix D: Function Blocks
November 2014
Function Blocks
Status handling
Normally, the status of the PV reflects the status of the measurement value, the operating
condition of the I/O card, and any active alarm condition. In Auto mode, OUT reflects the value
and status quality of the PV. In Man mode, the OUT status constant limit is set to indicate that
the value is a constant and the OUT status is Good.
If the sensor limit exceeds the high or low range, PV status is set high or low and EU range status
is set to uncertain.
In the STATUS_OPTS parameter, select from the following options to control the status
handling.
BAD if limited
Sets the OUT status quality to Bad when the value is higher or lower than the sensor limits.
Uncertain if limited
Sets the OUT status quality to Uncertain when the value is higher or lower than the sensor
limits.
Uncertain if in manual mode
The status of the Output is set to Uncertain when the mode is set to Manual.
Notes
1. The instrument must be in OOS mode to set the status option.
2. The AI block only supports the BAD if Limited option, uncertain if limited, and uncertain if
manual.
Advanced features
The AI function block provided with Rosemount
®
fieldbus devices provides added capability
through the addition of the following parameters:
ALARM_TYPE
Allows one or more of the process alarm conditions detected by the AI function block to be
used in setting its OUT_D parameter.
OUT_D
Discrete output of the AI function block based on the detection of process alarm
condition(s). This parameter may be linked to other function blocks that require a discrete
input based on the detected alarm condition.
STD_DEV and CAP_STDDEV
Diagnostic parameters that can be used to determine the variability of the process.
Application information
The configuration of the AI function block and its associated output channels depends on the
specific application. A typical configuration for the AI block involves the following parameters:
CHANNEL
The device supports more than one measurement, so verify that the selected channel
contains the appropriate measurement or derived value. Refer to Table 3-8 on page 36 for a
listing of available channels on the 848T.
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