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Glossary
PID control
A common control strategy in which a process variable is measured and
compared to a desired set point to determine an error signal. A proportional
gain (P) is applied to the error signal, an integral gain (I) is applied to the
integral of the error signal, and a derivative gain (D) is applied to the
derivative of the error signal. The controller output is a linear combination
of the three resulting values.
PID controller
A controller that produces proportional plus integral (reset) plus derivative
(rate) control action.
process gain (K)
For a linear process, the ratio of the magnitudes of the measured process
response to that of the manipulated variable.
process variable (PV)
The measured variable (such as pressure or temperature) in a process
to be controlled.
proportional action
Control response in which the output is proportional to the input.
proportional band (PB)
The change in input required to produce a full range change in output due
to proportional control action. PB = 100 /Kc.
proportional kick
The response of a proportional controller to a step change in the setpoint
or process variable.
PSI
Pounds per square inch.
Q
Quarter Decay Ratio
A response in which the amplitude of each oscillation is one-quarter that
of the previous oscillation.
R
ramp
The total (transient plus steady-state) time response resulting from a sudden
increase in the rate of change from zero to some finite value of the input
stimulus. Also called ramp response.
rate action
Control response to the time rate of change of a variable. Also called
derivative control action.
reentrant execution
Mode in which calls to multiple instances of a subVI can execute in parallel
with distinct and separate data storage.
© National Instruments Corporation
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PID Control Toolkit User Manual