Industrial Control Vocabulary Flashcards
Industrial control system
Receive data from remote sensors measuring process variables, compare these with desired set points, and derive command functions which are used to control a process through the finite control elements such as control valves
Discrete controller
Single control loop, panel mounted which allows direct viewing of the front panel and provides means of manual intervention by operator, either to manually control the process or to change control set points
Process variables
The current measured value of a particular part of a process which is being monitored or controlled
Set point
The desired target value for an essential variable or a process value of a system. Departure of such a variable from its set points t is one basis for error-controlled regulation using negative feedback for automatic control
Control valve
A valve used to control fluid flow by varying the size of the flow passage as directed from a signal from a controller. This enables direct control of the flow rate and the consequential control of process quantities such as pressure temperature and liquid level
Distributed Control System (DCS)
A digital control system for a process or plant wherein controller functions and field connection modules are distribute throughout the entire system
SCADA
Supervisory control and data acquisition system
A control system architecture that uses computers networked data communications and graphical user interfaces for high level supervisory management but uses other peripheral devices such as programmable logic controllers and discrete PID controllers to interface to the process plant or machinery. The operator interfaces enabling monitoring and the issuing of process commands, such as controller set point changes, are handled through a SCADA supervisory computer system
PLC
Programmable logic controller
An industrial digital computer which has been ruggedized and adapted for the control of manufacturing processes
PID Controller
Proportional-integral-derivative controller
A control loop feedback mechanism widely used in industrial control systems. A PID controller continuously calculates an error value as the difference as the difference between a desired set point and a measured process variable and applies a correction based in proportional, integral, and derivative terms.
It automatically applies accurate and responsive correction to a control function
Ladder logic
A written method to document the design and construction of relay racks as used in manufacturing and process control
Ladder logic has evolved into a programming language that represents a program by a graphical diagram based on the virus diagrams of relay logic hardware.
Ladder logic is used to develop software for programmable logic controllers used in industrial control applications
P-Proportional
Term P is proportional to the current value of the set point-process value error e(t). Using proportional control alone in a process with the compensation, such as temperature control, will result in an error between the set point and the actual process value, because it requires an error to generate the proportional response.
If there is no error, there is no response
I-Integral
Term I accounts for past values of the SP-PV error and integrates them over time to produce the I term. For example, if there is a residual SP-PV error after the application of proportional control, the integral seeks to eliminate the residual error by adding a control effect due to the historic cumulative value of the error.
When the error is eliminated, the integral term will cease to grow.
D-Derivative
Term D is a best estimate of the future trend of the SP-PV error, based on its current rate of change. It is sometimes called “anticipatory control” as it is effectively seeking to reduce the effect of the SP-PV error by exerting a control influence generated by the rate of error change.
