1. An electrical circuit useful in determining the value of a capacitor including: a first bilateral switch for flowing a charging current through a resistive element to an initially-depleted first capacitor of known value, thereby charging said first capacitor to the potential of a voltage reference over a resulting first time; a second bilateral switch for flowing a charging current through said resistive element to an initially depleted second capacitor, thereby charging said second capacitor to said potential over a resulting second time, and; means for determining said times.