Instruction Manual
Instruction Manual
D103434X012
Blocks
November 2014
91
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 [47] parameter. The priority of each alarm is set in the following
parameters:
D HI_PRI [50]
D HI_HI_PRI [48]
D LO_PRI [52]
D LO_LO_PRI [54]
D DV_HI_PRI [56]
D DV_LO_PRI [58]
Alarms are grouped into five levels of priority, as shown in table B‐10.
Table B‐10. PID Function Block Alarm Priorities
Priority Number Priority Description
(1)
0 The alarm is disabled
1
An alarm condition with a priority of 1 can be recognized by the system. The device monitors the alarm but does not report it
until requested by the host system.
2
An alarm condition with a priority of 2 is reported to the operator, but generally 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.
1. The priority classes “advise” and critical” have no relationship to Plant Web Alerts.
Application Information
The PID function block is a powerful, flexible control algorithm that is designed to work in a variety of control
strategies. The PID block is configured differently for different applications.
Block Errors
Table B‐11 lists conditions reported in the BLOCK_ERR [6] parameter. Conditions in italics are not applicable for the PID
block and are provided only for your reference.
Table B‐11. BLOCK_ERR Conditions
Condition Number Condition Name and Description
0 Other (NA)
1 Block Configuration Error—SHED_OPT or BYPASS set to 0
2 Link Configuration Error (NA)
3 Simulate Active (NA)
4 Local Override—The actual mode is LO and Track Enable is set.
5 Device Fault State Set (NA)
6 Device Needs Maintenance Soon (NA)
7 Input failure/process variable has Bad status—The parameter linked to IN is indicating a Bad status.
8 Output Failure (NA)
9 Memory Failure (NA)
10 Lost Static Data (NA)
11 Lost NV Data (NA)
12 Readback Check Failed (NA)
13 Device Needs Maintenance Now (NA)
14
Power Up—Set if devices was powered up with this block in Out of Service (OOS) mode. Cleared on first change of mode to
other than OOS.
15 Out of Service—The actual mode is Out of Service (OOS).