Drift compensation of oscillatory signals

When the mean level of a random oscillatory signal is subject to low-frequency fluctuation or drift, accurate measurement of the amplitude of the individual positive and negative peaks is difficult. An inexpensive drift compensating circuit is described, which effectively removes drift, dc offset, and low-frequency fluctuation of the mean of such signals permitting measurement of the individual maxima with acceptable accuracy. One example of a random oscillatory signal, which is subject to drift, is the strain induced in a ship's hull due to bending in waves. The drift compensation circuit described has been used as the basis for a “Zero Tracking” Extreme Strain Recorder. It is capable of recording the positive and negative maxima of eight drift-compensated signals every hour for over one year unattended on board ship.