Refractory monitoring temperature sensor and refractory erosion location measuring device

A sensor for simultaneously monitoring temperatures of a plurality of regions within a tube, and providing a signal indicative of the temperature in a hottest one of said plurality of regions, comprising:

• first and second metal electrodes, both electrodes having a first length and essentially consisting of the same metal, which are parallel and spaced apart at a fixed distance, each electrode extending over the regions to be monitored within the tube;
• wherein said first electrode (27-1) extends along a central axis of said tube and said second electrode (27-2) extends parallel thereto;
• a third electrode (27-3) having a second length which is shorter than said first length and extending parallel to the first electrode within the tube;
• a fourth electrode (27-4) having a third length which is shorter than said second length and extending parallel to said first electrode within said tube;
• wherein said second, third and fourth electrodes define a radial array surrounding said first electrode;
• an insulating substance (2) filling the volume between said electrodes and extending over the regions to be monitored, said insulating substance having a resistivity which continuously decreases with increasing temperature, within a temperature range to be monitored which is between 800.degree. C. and a melting point of the electrodes, said substance remaining solid over said range;
• and
• wherein current flowing from one electrode, through the insulating substance, to another electrode, is shunted to the region having a highest temperature, due to a lower resistance of the insulating substance in said region having the highest temperature, thereby providing an output signal corresponding to resistance of said region having the highest temperature.