Method of detecting steady-state convergence of a signal

A method for detecting steady-state convergence of a signal compares a filtered version of the signal or its derivative to a threshold over a given time interval, and a measure of the signal variability is used to tune the filter behavior. In one implementation, the signal is filtered with a high-pass filter, and the cut-off frequency of the filter is adjusted inversely with respect to the measured variability of the signal. In another implementation, the signal derivative is filtered with a low-pass filter, and the cut-off frequency of the filter is adjusted in proportion to the measured variability of the signal. In each case, the variability of the signal is measured by computing a differential of the signal and then smoothing the differential.