Emerson Rosemount OCX 8800, Instruction Manual

Page: 148 / 306

Section 7: Foundation
Fieldbus
April 2017
Instruction Manual
IM-106-880C, OI
12
2
Status
Handling
7.11.11 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.
The Uncertain - EU range violation status is always set, and the PV status is set high- or low-
limited if the sensor limits for conversion are exceeded.
In the STATUS_OPTS parameter, you can 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.
NOTE:
The instrument must be in Manual or Out of Service mode to set the status option.
NOTE:
The AI block only supports the BAD if Limited option. Unsupported options are not grayed out;
they appear on the screen in the same manner as supported options.
7.11.12 Advanced Features
The AI function block provided with Fisher-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.
• VAR_SCAN – Time period in seconds over which the variability index (VAR_INDEX) is
computed.
• VAR_INDEX – Process variability index measured as the integral of average absolute
error between PV and its mean value over the previous evaluation period. This index is
calculated as a percent of OUT span and is updated at the end of the time period
defined by VAR_SCAN.