Patent US 4,675,804

A variable gain integrator for controlling the response time of a controlled device so as to control a condition. The condition is sensed and compared to a set point to determine an error representing the difference therebetween. The difference is integrated by the variable gain integrator, the output of which is used to control the controlled device. The control system monitors the rate of change of the sensed condition. When the rate of condition change is less than a reference, the gain of the integrator is increased to decrease the response time of the controlled device.