West Control Solutions ProVU 4 - Manual (Page 139)

ProVU4 Controller, Profiler & Recorder/Controller - Product Manual
Page 138 Glossary 59407, Issue 1 – March 2008
Control Deviation
Control Deviation is the difference between the Process Variable value and the Actual
Setpoint. The Control deviation error is equal to PV – SP. This value can be monitored using
a Deviation Alarm.
Also refer to: Actual Setpoint, Alarm Types, Deviation Alarm, Process Variable and Setpoint
Control Action
The primary power output direction. Reverse action is typically used with heating applications
as it increases the correcting variable as the process variable falls. A secondary output’s
action is always the opposite of the primary output.
Settings = Reverse or Direct
Default value = Reverse.
Also refer to: Control Type, Correcting Variable, Direct Acting Control and Reverse Acting
Control.
Control Enable/Disable
The PID controller outputs can be temporarily turned off by disabling the control. All other
functions continue as normal. The control enable/disable function can be controlled from the
Control Configuration sub-menu or optionally from Operation Mode or via a digital input if one
is fitted.
Also refer to: Configuration Menu, Digital Input, Operation Mode and PID
Control Type
This defines if a controller has unidirectional (Single) or bidirectional (Dual) control outputs.
Single outputs have a Primary output only. This can drive the PV in one direction (e.g. heat
only, cool only, increase humidity etc). Dual outputs have both Primary and Secondary
outputs which can force the PV to increase or decrease (e.g heat & cool, humidify and
dehumidify etc).
Settings = Single or Dual
Default value = Single.
Also refer to: Control Action, PID, Primary Proportional Band, Process Variable, and
Secondary Proportional Band.
Controller
An instrument that controls a process variable to a target setpoint, by applying a correcting
variable. The controller uses proportional (P, PI, PD o PID) or On-Off control methods.
Also refer to: Correcting Variable, Indicator, Limit Controller, On-Off Control, PD Control, PI
Control, PID, Process Variable, Proportional Control, Profiler and Setpoint.
Controller Mode
The normal mode of operation of the instrument when profiling is not fitted or it is not being
used.
Also refer to: Controller. Profiler and Profiler Mode
Correcting Variable
The amount of output from a controller used to adjust the process variable value up or down,
to remove any control deviation. The correcting variable is commonly referred to as the
controller output power.
Also refer to: Control Deviation, PID, Primary Power Output Limit and Process Variable