Sensor system for an impressed cathodic protection circuit

Claim 1

A surveillance apparatus for instantaneously sensing a cathodic protection current flowing in a cathodic protection circuit, comprising: an energizing circuit including a regulator network connected to a primary source of energy, said network converting the receiving energy to a useful, direct-current potential for impressing a sufficient cathodic protection current to a conductor subject to corrosion; a potentiometer connected in parallel with a branch of said cathodic protection circuit, said potentiometer having a pair of output terminals and an adjustable center tap for developing an adjustable potential difference between said output terminals; a comparator having an output terminal and a pair of input terminals connected to said output terminals of said potentiometer for instantaneously sensing the potential difference therebetween; a storage battery; a switching network having a first input connected to the output of said comparator, and a second input connected to said energizing circuit and to said storage battery; and a signaling device having a pair of input terminals connected through said switching network to said energizing circuit and to said storage battery, said signaling device becoming energized either by said energizing circuit or by said storage battery depending on the condition of said switching means, said signaling device having a non-signaling state when said potential difference is above a threshold level, and a signaling state when said potential difference drops to said threshold level.