Series of actions resulting in a change or change of state
Process
changes the state of fluid inside a system
Process System
Measures a process system variable and causes an action to maintain the process system variable at the desired value
Process Control System
Condition, property or quantity that is being measured
Measured Variable
Process system variable that is controlled at a desired value
Controlled Variable
Process system variable that is acted on directly by the control action.
Manipulated Variable
Information collected by control system
Control System Input
Signal produced by control system to adjust the controlled variable.
Control System Output
Desired value/setting for controlled variable.
Setpoint
Difference between setpoint and measured variable.
Error Signal
System response monitored in a closed loop system.
Feedback
Measure and indicate process parameters without any conversion.
Direct Measurement
Measuring devices that sense a physical property of the system and convert a change in that property into an indication.
Indirect Measurement Instrument
Limits in which a quantity can be measured. It’s expressed by the lowest and highest quantity the device can measure.
Range
Algebraic difference between highest and lowest values of quantity.
Span
Ability of an instrument to measure the actual parameters value.
Accuracy
Degree of agreement between repeated results.
Precision
Slow changing of the displayed indication without changes in the system parameter.
Drift
Measure of how well it can detect and indicate small changes in input.
Sensitivity
Typically a numerical display of an instantaneous value of the measured variable.
Digital Display
Continuous display representative of the process, has a range and span. Displayed in two ways: pointer moves on a fixed scale or pointer is fixed and scale moves.
Analog Display
Apparent change in position of an object resulting from a change in position or direction from which object is viewed.
Parallax
Do not ______ an analog display reading into specification. Record actual reading, contact supervisor.
Round off
Indicator has input signal greater than 0 when it is indicating 0. Gives operator indication that instrument has failed.
Live Zero