Rosemount OCX 8800, Instruction Manual

Page: 143 / 266

Instruction Manual
IM-106-880, Rev 2.1
April 2017
OCX 8800
7-43
Alarm Detection
A block alarm will be generated whenever the BLOCK_ERR has an error bit
set. The types of block error for the AI block are defined above.
Process alarm detection is based on the PV value. You can configure the
alarm limits of the following standard alarms:
• High (HI_LIM)
• High high (HI_HI_LIM)
• Low (LO_LIM)
• Low low (LO_LO_LIM)
Additional process alarm detection is based on the difference between SP
and PV values and can be configured via the following parameters:
• Deviation high (DV_HI_LIM)
• Deviation low (DV_LO_LIM)
In order to avoid alarm chattering when the variable is oscillating around the
alarm limit, an alarm hysteresis in percent of the PV span can be set using the
ALARM_HYS parameter. The priority of each alarm is set in the following
parameters:
• HI_PRI
• HI_HI_PRI
• LO_PRI
• LO_LO_PRI
• DV_HI_PRI
• DV_LO_PRI
Alarms are grouped into five levels of priority:
Priority Number Priority Description
0 The priority of an alarm condition changes to after the condition that
caused the alarm is corrected.
1 An alarm condition with a priority of 1 is recognized by the system, but is
not reported to the operator.
2 An alarm condition with a priority of 2 is reported to the operator, but does
not require operator attention (such as diagnostics and system alerts).
3-7 Alarm conditions of priority 3 to 7 are advisory alarms of increasing priority.
10-15 Alarm conditions of priority 8 to 15 are critical alarms of increasing priority.
Status Handling
If the input status on the PID block is Bad, the mode of the block reverts to
Manual . In addition, you can select the Target to Manual if Bad IN status
option to direct the target mode to revert to manual. You can set the status
option in
Manual or Out of Service mode only.
NOTE
Target to Manual if Bad IN
is the only status option supported by the PID
function block. Unsupported options are not grayed out; they appear on the
screen in the same manner as supported options.