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Alarm Types
There are three basic alarm types, Process Alarms,
Control Deviation Alarms and Event Based Alarms;
plus some special condition alarms. Process Alarms
are based on the absolute value of the Process Vari-
able. If the PV rises above a high alarm value, or falls
below a low alarm value, the alarm will become active.
Control 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. Event based alarms activate when the
condition for that alarm type is true. These can be Sig-
nal Break, Low Memory or Loop Alarms. Rate of Signal
Change Alarm is based on the rate of change of the PV.
If the rate of change is greater than the alarm value for
longer than the Minimum Duration time, the alarm will
activate. Control Power High and Control Power Low
alarms are based on the output power from the PID
control algorithm.
Also refer to: Alarm Operation; Band Alarm Value; Con-
trol Deviation; Control Power Alarm; Deviation Alarm;
Loop Alarm; PID; Process High Alarm; Process Low
Alarm; Process Variable; Rate Of Change Alarm; and
Setpoint.
Alternate Setpoint
The instrument can use one of two setpoints (Main or
Alternate). The alternate setpoint can be chosen from
Local Setpoint 2 or a remote setpoint input from Auxil-
iary Input A if fitted. One setpoint can be chosen as the
active at using the setpoint selection screen.
Also refer to: Auxiliary Input; Local Setpoints; Main
Setpoint; Profiler; Remote Setpoints; Setpoint and Set-
point Select.
Auto Pre-Tune
When the auto pre-tune is enabled, a pre-tune activa-
tion 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 signifi-
cantly 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.
Also refer to: Pre-Tune; Self-Tune; PID and Tuning.
Automatic Reset
- Refer to Integral Action
Auxiliary Input
A secondary linear input module can be installed in op-
tion slot A to provide a remote setpoint input. Signals
can be mA, or VDC. The 2nd Universal input can also
be used as an auxiliary input if fitted. Also refer to: Al-
ternate Setpoint; Digital Input; Linear Input; mADC; Re-
mote Setpoint and VDC
Auxiliary Input Lower Limit
When auxiliary input A is used to provide a remote set-
point (RSP), this setting defines the Alternate Setpoint
value when the auxiliary input signal is at its minimum
value (e.g. for 4 to 20mA, the value when 4mA is ap-
plied). However, the setpoint is always constrained by
the setpoint limits.
Also refer to: Alternate Setpoint; Auxiliary Input; Aux-
iliary Input Upper Limit; Auxiliary Input Offset; Remote
Setpoint; Setpoint and Setpoint Upper Limit and Set-
point Lower Limit.
Auxiliary Input Offset
Used to adjust the value of auxiliary input A if it pro-
vides a Remote Setpoint. Positive values are added
to the remote setpoint value, negative values are sub-
tracted, but the setpoint is still constrained by the set-
point limits.
Also refer to: Auxiliary Input; Remote Setpoint; Scaled
Input Upper Limit; Scaled Input Lower Limit Setpoint
Lower Limit and Setpoint Upper Limit.
Auxiliary Input Type
Defines the type and range of the linear input signal for
auxiliary input A. It can be mADC or VDC. This can be
used as a Remote Setpoint input.
Also refer to: Remote Setpoint and Setpoint.
Auxiliary Input Upper Limit
When the auxiliary input is used to provide a Remote
Setpoint (RSP), this setting defines the value of the
RSP when the auxiliary input signal is at its maximum
value (e.g. for 4 to 20mA, the value when 20mA is ap-
plied). However, the RSP value is always constrained
by the setpoint limits.
Also refer to: Auxiliary Input; Auxiliary Input Lower Lim-
it; Auxiliary Input Offset; Remote Setpoint; Setpoint and
Setpoint Upper Limit and Setpoint Lower Limit.
Band Alarm Value
The amount of control deviation that is acceptable be-
fore a Band Alarm is activated. If the process variable
is more than the value of this band from the actual set-
point, the alarm will be active.
Also refer to: Actual Setpoint; Alarm Operation; Alarm
Types; Control Deviation; Input Span; LSD and Process
Variable.
Bar Graphs
The instrument displays uni or bi-directional bar-graphs
in the operation mode for loop 1 & 2 PID power (single
control = 0 to 100%, dual control = -100% to +100%),
control deviation (-5% to +5%) and % Recorder Mem-
ory Used (0 to 100%). In Profiler Mode, profile & current
segment bar-graphs are shown (0 to 100%).
Also refer to: Control Deviation; Data Recorder; Display
Configuration; Operation Mode; Main Menu; PID & Profiler.
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