Temperature sensing cable device and method of making same

A method of remote overheat detection of an area for use with an elongate temperature sensing cable formed of a composition having at least one polymeric component and an amount of electrically conductive particles therein to promote a negative temperature coefficient characteristic of the composition when above an anomaly temperature and in a presence of an electric field sufficient to promote tunneling conduction current in said composition, the method comprising the steps of:

• extending a predefined length of the electrical temperature sensing cable into said area;
• applying said electric field to at least a portion of the composition in the area;
• detecting the tunneling conduction current flow through the composition in a presence of the overheat condition above said anomaly temperature;
• and,
• generating an alarm signal when the tunneling conduction current flow is detected.

An overheat alarm system for detecting an overheat condition in an area, the system comprising:

• an elongate temperature sensing cable extended over a first length in said area, the cable being formed of a composition having at least one polymeric component and an amount of electrically conductive particles therein to promote a negative temperature coefficient characteristic of the composition when above an anomaly temperature and in the presence of an electric field sufficient to promote tunneling conduction current in said composition;
• at least two electrical conductor means for conducting electrical current, the at least two electrical conductor means being electrically interconnected by said composition;
• supply means for applying said electric field through the at least two electrical conductor means to at least a portion of the composition in the area;
• tunneling current detecting means for detecting a tunneling conduction current flow through the composition in a presence of the overheat condition above said anomaly temperature in said area;
• and,
• alarm generating means for generating an alarm signal when the tunneling conduction current flow is detected.

An overheat alarm system comprising:

• a temperature sensing element having a negative temperature coefficient of electrical resistance above an anomaly temperature, the element comprising:
• a composition exhibiting reversible electrical behavior, the composition containing at least one polymeric component and an amount of blended electrically conductive carbon black and zinc oxide particles therein to promote a reversible negative temperature coefficient characteristic of the composition when above the anomaly temperature and in a presence of an electric field sufficient to promote conduction in said composition;
• and,
• at least two electrical conduction means, electrically interconnected through the composition, for conducting electric current in said temperature sensing element;
• supply means for applying said electric field to said at least two electrical conduction means;
• tunneling current detecting means for detecting a tunneling conduction current flow through the composition in a presence of the overheat condition above said anomaly temperature;
• and,
• alarm generating means for generating an alarm signal when the tunneling conduction current flow is detected.