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TAU - APMonitor Option

 Type: Floating Point, Input
 Default Value: 1.0
 Description: Time constant for controlled variable response

The time constant is a tuning parameter for the speed of response of a reference trajectory. When the set point is stepped to a new value, the time constant (TAU) adjusts the speed of response with

$$SP_{tr} = \left(1-\exp{\left(-\frac{t}{TAU}\right)}\right) (SP_{new} - SP_{old}) + SP_{old}$$

where SPold is the prior set point, SPnew is the new set point, t is the time, TAU is the time constant, and SPtr is the resultant trajectory.

See also SP, SPHI, SPLO