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C-9
PID Function Block
RemoteOutput (Rout)—The OUT IS provided by a host computer that
writes to the ROUT_IN parameter
Local Override (LO)—The track function is active. OUT is set by
TRK_VAL. The BLOCK_ERR parameter shows Local override.
Initialization Manual (IMan)—The output path is not complete (for
example, the cascade-to-slave path might not be open). In IMan mode,
OUT tracks BKCAL_IN.
Out of Service (O/S)—The block is not processed. The OUT status is
set to Bad: Out of Service. The BLOCK_ERR parameter shows
Out of service.
You can configure the Man, Auto, Cas, and O/S modes as permitted
modes for operator entry.
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 0 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.
8-15 Alarm conditions of priority 8 to 15 are critical alarms of increasing priority.