Glossary
LabWindows/CVI PID Control Toolkit User Manual G-4 ni.com
O
output limiting Preventing a controller’s output from traveling beyond a desired maximum
range.
overshoot The maximum excursion beyond the final steady-state value of output as
the result of an input change.
P
P Proportional.
PD Proportional, derivative.
PI Proportional, integral.
PID Proportional, integral, derivative.
PID control A common control strategy in which a process variable is measured and
compared to a desired setpoint 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.
PSI Pounds per square inch.