Use of diaphragm transducers in the measurement of pressures on soft materials.

Diaphragm pressure transducers are designed to measure pressures in fluids, but have also been applied to measuring pressures on soft materials, such as at the interface between the residual limb of a lower-limb amputee and the supporting surface defined by the prosthetic socket. The reliability and accuracy of Kulite XTM-190 transducer as a pressure monitor on soft materials, such as silicone and Pelite was evaluated in three physical model set-ups. The evaluations included the uniform loading of solid disks of silicone and Pelite, the application of air pressure to the core of a contained thick-walled cylinder made of silicone, and the dynamic indentation of a contained solid silicone cylinder. Sensor measurements in all situations were similar to analytical, iterative or finite element solutions when certain conditions were met. These conditions include: (i) lubricating the interface between the soft material and the supporting structure; (ii) calibrating the transducers under surface and material conditions used during measurements; and (iii) using compatible soft materials (e.g. silicone but not Pelite).