Abstract: Apparatus for measuring the time integral of a signal between pairs of time points comprises a ramp voltage generator and a plurality of pairs of potentiometers. A comparator circuit is associated with each potentiometer to provide a switching signal at the time point when the ramp voltage becomes equal to the potentiometer voltage. The switching signals are applied to a gate which is held open between each pair of time points to allow the signal to be measured to be passed to a suitable measuring means. Such measuring means may comprise a voltage-to-frequency converter and a counter so that the output of the counter represents the time integral of the signal.