West Control Solutions Pro-EC44 - Manual (Page 233)

Pro-EC44 2-Loop Graphical Profile Controller & Recorder
Pro-EC44 Product Manual - 59540-1 October 2013 Page 226
Profiler
A profiler controls the value of the actual setpoint over time; increasing, decreasing or
holding its value as required. This is used in applications where the rate of rise or fall of the
process variable must be closely controlled, or where a value must be maintained for a
period before moving to the next value. If the Profiler is fitted, up to 64 profiles can be
created with 255 segments shared amongst them. These profiles can control the setpoints
for loop 1 only or both loops. Each segment can activate/deactivate the five events.
Refer to the Profiler Option section.
Also refer to: Actual Setpoint; Controller Mode; Profile Events; Profile Control Menu; Profile
Header; Profile Segments; Profile Setup Menu and Profiler Mode.
Profiler Mode
This mode is entered when a profile is selected or run. The instrument will remain in profiler
mode when the profile finishes or is aborted, unless the segment end type/profile abort action
is set to “Use Controller Setpoint”.
Also refer to: Controller Mode; Profile Control Menu; Profile Segments; Profile Setup Menu;
Profiler and Setpoint.
Proportional Control
Proportional control gradually changes the correcting variable applied from 0 to 100% of the
available power
as the process moves through the “Proportional Band”. If the control type is
dual, both primary & secondary outputs available, equating to -100 to +100%. When the
proportional bands are correctly tuned, the process is maintained at a steady value, avoiding
the oscillation characteristic of on-off control. Proportional control is commonly used in
conjunction with integral and derivative action to give PI. PD or PID control.
Also refer to: Control Type; Correcting Variable; Derivative Action; Integral Action; PD; PI;
PID; Primary Proportional Band; Process Variable; Secondary Proportional Band; and
Tuning.
Rate
- Refer to Derivative Action.
Rate of Change Alarm
An alarm based on the rate of change in the measured process variable. If the PV changes
at a rate greater than the alarm level, the alarm will activate. The rate of change must be
above the alarm threshold for longer than the alarm minimum duration time before the alarm
will change state (from on to off, or off to on).
Caution: If the duration is less than this
time, the alarm will not activate no matter how fast the rate of rise.
Also refer to: Alarm Hysteresis; Alarm Minimum Duration; Alarm Operation; Alarm Types and
Process Variable.
Ratio Control
Ratio control is where part of the process is controlled in proportion to another part. For
example, it could mix two materials at a desired ratio by adjusting the flow of input 1 in
relation to the flow measured by input 2. The flow of input 2 may be controlled separately, but
not by the ratio loop. If two process inputs are fitted, this instrument can be configured for
stoichiometric combustion control, where the fuel-air ratio is controlled for a burner.
Refer to the Ratio Control section of this manual for full details.
Also refer to: Controller; PID and Process Variable.