Automatic correction for drift in an integrator for phasic signals

Abstract

An electronic integrator for phasic signals has been designed that does not undergo slow changes in output voltage (drift). Output is stabilised by means of negative feedback using an active 5-pole lowpass filter. Accurate integration of phasic signals with frequencies above 0·1 Hz is obtained. The integrator has been used for continuous determination of cyclincal volume changes, with a pneumotachograph as an input source, in the plotting of respiratory pressure-volume loops.