Owner's manual

9-9
Proportional/Integral/Derivative (PID) Function Block
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:
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.
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.