Glossary

ARC

Advanced Regulatory Control; An Advanced Process Control algorithm built primarily using commonly available building blocks (or “function blocks”) within DCS and PLC controllers. Despite the use of the term “Regulatory”, there is no restriction of the use of ARC to regulatory functions at all; However it is the only common term used to distinguish control implemented in these types of DCS and PLC platforms.

ARIMA

Auto-Regressive-Integrating-Moving-Average difference-equation dynamic model.

CO

Controller Output; the value of the output of a feedback controller. Also known as a Manipulated Variable (MV).

Control Selection Table

See Control Selection Table.

loop

Generally refers to a combination of the controlled system (input to output), connected with a feedback controller in a closed-loop or path, with system output connected to the controller’s PV input and the controller’s output (CO) connected to the system input.

MA filter

Moving-Average filter; Usually used to reduce the amplitude of unwanted noise on a signal.

PI controller

A PID controller without derivative action, usually resulting in comparatively lower performance.

PID controller

A Proportional-Integral-Derivative feedback controller algorithm, commonly available within Distributed Control System (DCS), Programmable Logic Controllers (PLC) and Programmable Automation Controllers (PAC).

PV

Plant Variable, Process Value or Present Value; the value of a measurement from the process plant or a calculated variable; also known as a Controlled Variable (CV). A PV is commonly designated as an input of a feedback controller.

SP

Set-Point; the value of an operator or automatically determined target for a controller to drive a PV towards. An alternate name is Reference Variable (RV). A SP is commonly designated as an input of a feedback controller.