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DCP200 Profile Controller & Recorder - Product Manual
51-52-25-150, Issue 1 – April 2009 Glossary Page 135
Alarm Inhibit
Alarm Inhibit prevents unwanted process or deviation alarm activation at power-up or when
the controller setpoint is changed. The alarm activation is inhibited until a ‘Safe’ condition is
present. The alarm operates normally from that point onwards. E.g. if inhibited, a low alarm
will not activate at power-up, until the process has first risen above the alarm point and then
falls back below.
Settings = Inhibit or not inhibited for each alarm. Default value = None Inhibited.
Also refer to: Alarm Types and Alarm Operation.
Alarm Types
There are four basic alarm types, Process Alarms, Control Deviation Alarms, Rate of Signal
Change Alarms and Event Based Alarms.
Process Alarms are based on the absolute value of the Process Variable. If the PV rises
above a high alarm value, or falls below a low alarm value, the alarm will become active.
Deviation Alarms are based on the value of the Control Deviation error. If the PV is more
than the high deviation alarm value above setpoint, or more than the low deviation alarm
value below setpoint, the alarm will become active.
Rate Of Signal Change Alarms are based on the rate of change of the PV. If the rate of
change is greater than the alarm value for longer that the Minimum Duration time, the alarm
will activate.
Event based alarms activate when the condition for that alarm type is true. These can be
Signal Break, Low Memory Or Loop Alarms.
Also refer to: Alarm Operation, Band Alarm Value, Control Deviation, Deviation Alarm, Loop
Alarm, Process High Alarm, Process Low Alarm, Process Variable, Rate Of Change Alarm,
and Setpoint.
Alternative Setpoint
The instrument can have up to two setpoints. Local Setpoint 1 and/or an Alternative Setpoint.
The Alternative Setpoint can be chosen from Local Setpoint 2 or a remote setpoint input from
Auxiliary Input A or B if either of these are fitted. One setpoint can be chosen as the active at
using the Setpoint Selection.
Also refer to: Auxiliary Input, Local Setpoints, Remote Setpoints; Setpoint and Setpoint
Select.
Auto Pre-Tune
When the Auto Pre-Tune is enabled, a Pre-Tune activation is attempted at every power-up
(standard Pre-Tune activation rules apply). Auto Pre-Tune is useful when the process to be
controlled may vary significantly each time it is run. Auto Pre-Tune ensures that the process
is tuned correctly each time the process is started. Self-Tune may also be engaged to fine-
tune the controller.
Settings = Enabled or Disabled. Default value = Disabled.
Also refer to: Pre-Tune, Self-Tune, PID and Tuning.
Automatic Reset
- Refer to Integral Action