Pressure mapping system with capacitive measuring pad

Abstract

A pressure distribution measuring system includes a pad of insulating material disposed between two linear arrays of electrodes to form a matrix of capacitive nodes. A capacitance related output signal that is obtained from a node of interest is used as a feedback signal and applied to other capacitors that are connected in common with the node of interest. The feedback signal inhibits the flow of current through these commonly connected capacitors, and thereby isolates the measured signal from any changes in the capacitance of these other capacitors. The pad includes a cental array of linear electrodes sandwiched between two layers of dielectric foam material. Two outer, aligned linear electrode arrays, oriented perpendicular to the central array, are respectively disposed on the outside surfaces of the dielectric layers. In a preferred form, alternating electrodes in each outer array are located on opposite sides of a support substrate. This construction increases the amplitude of the measured signal, isolates the measured signal from the ambient environment, and reduces the susceptibility of the measuring process to errors caused by wrinkling of the pad as a person lies on it, or the like.