National Instruments 371685C-01 User Manual
Glossary
G-4
ni.com
O
output limiting
Preventing a controller’s output from traveling beyond a desired maximum
range.
range.
overshoot
The maximum excursion beyond the final steady-state value of output as
the result of an input change.
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.
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.
(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.
response to that of the manipulated variable.
process variable (PV)
The measured variable (such as pressure or temperature) in a process to be
controlled.
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/K
to proportional control action. PB = 100/K
c
.
PSI
Pounds per square inch.