Abstract: A probe for measuring heat includes an elongate rod fitted within a sheath, and a plurality of annular recesses are formed on the surface of the rod in a spaced-apart relationship to form annular chambers that are resistant to heat flow. A longitudinal bore extends axially into the rod and within the cylinders defined by the annular chambers, and an integrated heater and thermocouple pack is dimensioned to fit within the bore. In construction, the integrated pack includes a plurality of wires disposed in electrical insulation within a sheath and a heater cable. These wires include one common wire and a plurality of thermocuple wires. The common wire is constructed of one type of conductive material while the thermocouple wires are each constructed of two types of materials so that at least one thermocouple junction is formed therein. All of the wires extend the length of the integrated pack and are connected together at their ends.

Abstract: A method and apparatus are disclosed for detecting leaks in a liquid-containing tank. The method and apparatus employ an internal reference cell immersed in the liquid in the tank which contains a volume of the liquid isolated from flow communication with the liquid in the tank while having a surface which is exposed to the ambient conditions above the surface of the liquid in the tank. The level of the fluid in the tank and in the reference cell are monitored over a period of time. Level changes in the tank which do not correspond to level changes due to the temperature and evaporative effects observed in the reference cell are indicative of a leak in the tank.

Abstract: A measuring instrument includes a U-shaped probe that senses temperature and is useful for sensing the level of a liquid in a tank. A main probe unit has first and second legs disposed in a side-by-side, parallel relationship and a heater cable is contained within and along the length of the first leg. Heated sensors are disposed inside the first leg in positions proximate to the heater cable for sensing temperatures at a plurality of positions along the first leg, and non-heated sensors are disposed in the second leg for sensing temperatures at a plurality of positions along the second leg. An electrical circuit is connected to the heated temperature sensors and the non-heated temperature sensors for producing at least one signal indicating the temperatures of the heated sensors and preferably indicating the temperatures of the heated sensors relative to the non-heated sensors.

Abstract: A method and apparatus are disclosed for detecting leaks in a liquid-containing tank. The method and apparatus employ an internal reference cell immersed in the liquid in the tank which contains a volume of the liquid isolated from flow communication with the liquid in the tank while having a surface which is exposed to the ambient conditions above the surface of the liquid in the tank. The level of the fluid in the tank and in the reference cell are monitored over a period of time. Level changes in the tank which do not correspond to level changes due to the temperature and evaporative effects observed in the reference cell are indicative of a leak in the tank.

Abstract: The specification discloses a boundary detector for locating the boundary between two substances having different thermal absorption characteristics. In one embodiment, the detector monitors the level of a coolant in a vessel in which case the upper surface of the coolant constitutes the detected boundary. An elongate sensor is constructed of a plurality of segments of different material connected end-to-end to form a series of thermocouple junctions. This sensor is disposed across the boundary in the two substances, and a segmented heater cable is used to heat selected ones of the thermocouple junctions. The sensor and the heater cable are electrically insulated by thermally conductive material that will transfer heat to the substances in which the sensor is disposed, and because of this heat transfer, the temperatures of the heated junctions are, in part, dependent upon the substance in which it is located. By monitoring the voltage potential across the sensor, the boundary may be detected and located.