Automated Controls - Glossary Flashcards
How an indicated value conforms to an accepted standard value or true value.
Accuracy
Analog to digital converter
ADC [A/D]
A signal representing a variable which may be continuously observed and continuously represented.
Analogue signal
A decrease in signal magnitude. Also, the reciprocal of gain.
Attenuation
A signal path which includes a forward path, a feedback path, and a summing point, and forms a closed circuit.
Closed loop
The parameter that is desired to be controlled. e.g. temperature, flow rate, pressure, liquid level.
Controlled/process variable
A device which operates automatically to regulate a controlled variable.
Controller
Digital to analogue converter
DAC
Digital control system
DCS
Distributed (Direct) Digital Control - A building automation system in which a microprocessor based control system performs building automation digitally.
DDC
The range through which an input can be varied without initiating an observable response.
Dead-band
Control action in which the output is proportional to the rate of change of the input.
Derivative (rate) control action
Information represented by a set of binary numbers.
Digital signal
In a control loop, it is the variable which is sensed to originate a feed-back signal.
Directly controlled variable
Information represented by a set of separate and distinct numbers or values.
Discrete signal
A component of a device or system
Element
This is the signal derived in a closed loop control system from the difference between the set-point signal and the feed-back signal.
Error signal
The return signal which is generated from the measurement of the directly controlled variable.
Feed-back signal
It is the forward controlling element which directly changes the value of the manipulated variable.
Final control element
The ratio of the change in output due to proportional control action to the change in input.
Proportional gain
Control action in which the output is proportional to the time integral of the input.
Integral (reset) control action
A quantity of condition which is varied as a function of the actuating error signal so as to change the value of the directly controlled variable.
Manipulated variable
Resistance and temperature are inversely proportional.
NTC - Negative temperature coefficient
A signal path without a feedback.
Open loop
Physical or chemical change of matter or conversion of energy. e.g. change in temperature, pressure, temperature, electrical potential, speed, etc.
Process
Control action in which there is a continuous linear relation between the output and the input.
Proportional control action
Resistance and temperature are directly proportional.
PTC - Positive temperature coefficient
The region between two limits within a quantity is transmitted, measured or received.
Range
The smallest interval between sequential discrete values. e.g. the number of degrees per address produced by an absolute encoder.
Resolution
The element which directly responds to the measured variable.
Sensor (sensing element)
An input variable which determines the desired value of the controlled variable. It may be manually set, automatically set or programmed.
Set-point
The algebraic difference between the upper and the lower range values.
Span
A device element which converts energy from one type to another.
Transducer
A transducer which responds to a measured variable by means of sensor (sensing element) and converts it to a standardized transmission signal.
Transmitter
