A differential displacement transducer for measuring relative movement in biological systems

This article describes a modified and improved version of the displacement transducer design originally presented by Sandeman (1968). The present design generates a high frequency electric field in the bathing solution. Relative displacement is detected within this field by measuring the differential voltage between two small diameter wire-sensing electrodes, which can be attached to different biological structures. By placing one of the sensing electrodes at a fixed point within the bath, absolute displacement can also be measured. A brief theoretical discussion and complete design are presented for the differential displacement transducer. The method presented here is more sensitive and versatile than the original approach.