Automated Controls Flashcards
A part of the final control element that converts output signal into a force or energy that alters the process variable.
Actuator
Analog to Digital conversion
A to /D
An indication that some measured or controlled variable has exceeded some preset limit.
Alarm
Pertaining to a mechanism that represents data by measurement of a continuous physical variable, as voltage or pressure.
Analog
A pressure sensing element that converts a variable pressure input to a proportional force or displacement output.
Bellows
Representation of the control system in the simplest manner with each component shown by a block with input and output connections.
Block Diagram
A somewhat flatten tube which straightens out as more pressure is applied converting the pressure input into mechanical displacement.
Bourdon Tube
A controller produces a change in output signal in response to the error detected (difference between the desired value and actual value).
Closed Loop
Software or hardware which operates automatically to regulate a controlled variable. Compares the feedback signal to the set point signal and makes adjustments.
Controller
The function of measuring, transmitting and storing electrical signal information from sensors, transducers, and position indicators. Typically includes conversion into computer compatible format.
Data Acquisition
Distributed Control System, a microprocessor based system similar to a PLC but typically with multiple components distributed through the system and each of its components is controlled by a separate controller or controllers. This system of controllers is interconnected to each others for monitoring and communication.
DCS
The range in which an input may be changed without initiating any observable change in the output.
Dead Band
A component of a device or system.
Element
The difference between the desired value and the actual value of the process being controlled.
Error
Taking the error signal and sending it back to the controller for comparison to the set point.
Feedback
The component or equipment that converts the controller output signal into a type of energy that makes adjustments to the process variable.
Final Control Element
A method of expressing the sensitivity of magnitude of response to an input.
Gain
Human Machine Interface, used to allow operators to monitor or control a process, also called MMI (Man Machine Interface) or GUI (Graphic User Interface).
HMI
An instrument or control equipment in which electrical energy is limited or contained so that it is incapable of creating a spark or otherwise igniting a flammable mixture.
Intrinsically Safe
A sensor for the measurement of force or weight usually based on strain gauges.
Load Cell
Linear Variable Differential Transformer, an AC device which measures displacement and converts it to a linear output voltage.
LVDT
A restriction used to create a pressure drop proportional to the flow rate.
Nozzle
Control action in which the measured variable is compared to the desired value to produce a signal which is acted on to reduce the magnitude or the error.
Negative feedback
Difference between the desired value and the controlled variable when no changes are taking place.
Offset
No feedback is used. Human completes the loop.
Open loop
A simple type of restriction that creates a pressure drop proportional to the flow rate.
Orifice Plate
The amount that a controlled variable exceeds it’s desired variable after an adjustment.
Overshoot
Piping and Instrumentation Drawing or Diagram.
P + ID
Proportional Integral Derivative Control
PID
Feedback in which the error is added to the control signal resulting in a “runaway” condition.
Positive Feedback
First element in a system that responds quantitatively to the measured variable.
Primary Element
The variable that is controlled (temperature of an oven, level of a tank).
Process Variable
The difference between the stated maximum and minimum measurements values.
Range
The minimum amount that can be measured or controlled by a system or instrument.
Resolution
Resistance Temperature Detector
RTD
Remote Transmitter Unit
RTU
Supervisory Control and Data Acquisition, refers to centralized computer based systems which monitor and control entire sites or complexes of systems spread out over large areas (anything between an industrial plant and a country). The Process can be industrial, infrastructure or facility based.
SCADA
The change in output in response to a given input.
Sensitivity
A device that converts a physical, electrical, or chemical variable into a useful proportional signal. It (senses) the process variable and usually provides feedback to a controller.
Sensor
A control system primarily dedicated to position or velocity control.
Servo (Servomechanism)
Provides information to the controller about the desired value of the process.
Set Point
The condition where a balance is reached between the inputs of mass or energy to a system and the outputs of mass or energy from the system.
Steady State
A sensor made from semiconductor material which changes it’s electrical resistance with temperature : generally known for its negative co-efficient response to temperature change.
Thermistor
Two dissimilar wires used to create a millivolt thermoelectric temperature transducer.
Thermocouple (T/C)
An element or device which converts one form of quantity or energy into another.
Transducer
A device that converts a process variable measurement (temperature, flow, etc) into a suitable signal to be sent to a remote receiver (controller, recorder, etc).
Transmitter
