Definitions Flashcards
PROCESS CONTROL
THE AUTOMATIC HOLDING OF CERTAIN PROCESS VARIABLES WITHIN GIVEN LIMITS.
TRANSDUCER
A DEVICE THAT CHANGES ENERGY FROM ONE FORM TO ANOTHER.
FINAL CONTROL ELEMENT
THE PART OF THE CONTROL LOOP THAT RECEIVES A SIGNAL FROM THE CONTROLLER AND CONVERTS IT INTO AN ACTION THAT CAUSES THE MANIPULATED VARIABLE TO CHANGE.
TRANSMITTER
A DEVICE THAT CONDITIONS THE SIGNAL RECEIVED FROM A TRANSDUCER SO THAT IT CAN BE SENT SOME DISTANCE AWAY.
ANALOG
A CONTINUOUS OPERATING SIGNAL.
SENSOR
THE PART OF A CONTROL LOOP THAT SENSES THE VALUE OF A PROCESS VARIABLE.
ACTUATOR
THE PART OF THE FINAL CONTROL ELEMENT THAT CONVERTS AN INPUT SIGNAL INTO AN ACTION.
CONTROLLED VARIABLE
THE VARIABLE MEASURED TO INDICATE THE CONDITION OF THE OUTPUT OF THE PROCESS.
SPAN
THE DIFFERENCE BETWEEN THE LOWEST AND HIGHEST READING OF AN INSTRUMENT.
SET POINT
THOSE VALUES OVER WHICH A TRANSMITTER IS INTENDED TO MEASURE.
PROCESS VARIABLE
THE VARIABLE MEASURED TO INDICATE THE CONDITION OF THE OUTPUT OF THE PROCESS.
MODULATION
A COMPONENT, SUCH AS A VALVE, THAT THAT IS CAPABLE OF OPERATING AT ANY POSITION BETWEEN FULLY OPEN AND FULL CLOSED.
MANIPULATED VARIABLE
THE VARIABLE MANIPULATED BY THE FINAL CONTROL ELEMENT.
CONTROLLER
PROCESS CONTROL LOOP ELEMENT THAT DETERMINES WHAT ACTION NEEDS TO BE TAKEN.
MEASURED VARIABLE
THE VARIABLE MEASURED TO INDICATE THE CONDITION OF THE OUTPUT OF THE PROCESS.
RANGE
THE DESIRED VALUE WHERE THE PROCESS SHOULD BE MAINTAINED.
DEVIATION
THE DIFFERENCE BETWEEN THE MEASURED SIGNAL VALUE AND THE SET POINT.
INSTRUMENT
A DEVICE USED TO MEASURE AND/OR CONTROL A PROCESS VARIABLE.
ERROR
THE DIFFERENCE BETWEEN THE MEASURED SIGNAL VALUE AND THE SET POINT OR DESIRED VALUE.
LAG TIME
THE TIME REQUIRED TO RETURN A PROCESS VARIABLE TO ITS SET POINT FOLLOWING A DISTURBANCE.
DISTURBANCE
THE DEPARTURE FROM A DESIRED VALUE, USUALLY THE RESULT OF AN UNEXPECTED LOAD CHANGE.
SIGNAL
INFORMATION IN THE FORM OF A PNEUMATIC PRESSURE, AN ELECTRIC CURRENT, OR MECHANICAL POSITION THAT CARRIES INFORMATION FFROM ONE CONTROL COMPONENT TO ANOTHER.
LOOP
A SIGNAL PATH. A COMBINATION OF TWO OR MORE INSTRUMENTS OR CONTROL FUNCTIONS ARRANGED SO THAT SIGNALS PASS FROM ONE TO ANOTHER FOR THE PURPOSE OF MEASUREMENT OR CONTROL.
CLOSED LOOP
A COMBINATION OF CONTROL UNITS IN WHICH THE PROCESS VARIABLE IS MEASURED, COMPARED WITH THE SETPOINT, AND CORRECTED IF NECESSARY.
