1. In a process control apparatus having input means for inputting a first signal representing a setpoint for a process and a second signal representing a process variable, means for generating an error signal representing a difference between said first and second signals, and control means for providing a control signal for controlling the process as a function of said first and second signals, the improvement comprising: filter means connected to receive said first signal for generating a filtered setpoint signal; said filter means including: first means using a setpoint weighting factor .beta. for converting said first signal to said filtered setpoint signal, and second means for varying the setpoint weighting factor .beta. in response to a difference between said setpoint and said process variable represented by said error signal.