Resistive sensor for position detection of manifold failures

Abstract

An elongate resistive sensor useful as an element of a pneumatic manifold failure detecting and locating system. A sensing loop is based on a coaxial cable having a core of known resistance per unit length. A eutectic salt impregnated insulant separates the core and sheath but has a temperature breakdown characteristic which provides the sensing function. Upon a pneumatic manifold failure, the sensing cable is heated, the eutectic salt insulator breaks down, a core-to-sheath short occurs, and currents in the sensing cable are substantially altered as a result. The cable is connected as a loop, and differential currents into the ends of the loop are detected and processed to determine the position of the short. Terminating resistors are associated with connectors which connect multiple cable sections into a single loop, and the terminating impedance is further sensed to determine an open circuit condition at any connector.