An RTD (resistance temperature sensor or detector) sensing device which is a long, thin, unitary device adapted to be distributed across an extended field for the continuous, uninterrupted sensing or interrogation of such field, avoiding the inaccuracy, unreliability, and excessive expense of conventional "point" RTD and thermocouple sensors currently employed for this purpose. According to the invention, a very long, thin, ductile protective metal outer sheath houses a coextensive body of insulation material, which in turn supports and electrically insulates one or more coextensive RTD filaments and in most forms of the invention one or more heater filaments. Distributed RTDs of the invention may, along their lengths, have continuous linear function sensitivity, continuous variable function sensitivity, or step function sensitivity. Distributed RTDs of the invention have particular utility for gauging liquid level, measuring average mass flow velocity of fluids in large ducts, and sensing the average temperature of an extended nonisothermal field.
An electrical resistance temperature sensor (11) contained in a stainless steel, tubular jacket (12), which has a very small diameter of approximately 1 mm, a platinum resistance coil (18) running between two joining bolts (14, 19). The resistance coil with a positive temperature characteristic of the resistance is placed in an embedding medium (17), which comprises a mixture of magnesium oxide or aluminium oxide and cerium dioxide. For use as an integrating temperature sensor for a catalytic converter, said adequately flexible temperature sensor can be wound into a roll of smooth and corrugated metal sheets and fixed by soldering in vacuo.
A thermal dispersion switch/transmitter for determining flow rate and liquid level in a non-contacting apparatus. A special preparation of one or more small spots in the outside surface of the wall of the conduit, standpipe or container enables one or more thermally sensitive elements to reside very close to the fluid on the opposite side of the wall. A temperature sensor is formed of a raster pattern electrical conductor deposited on a thin, electrically insulative, thermally conductive flat chip. One temperature sensor is time-shared and is periodically self heated and functions as the reference as well as the active or heated sensor of the invention. One alternative is to employ two temperature sensors, one being a reference sensor and the other being the active sensor. An alternative embodiment employs the same construction of one or more small, very thin membrane surfaces to which multiple detectors are mounted inside a probe inserted into the conduit. A second alternative embodiment employs the same construction of a very thin, small area spot on the outside of a probe inserted into a conduit or vessel for flow rate, liquid level, or interface sensing. Other embodiments are shown and described. All of the embodiments employ a miniature temperature sensor with the sensing element being self heated, the switch/transmitter being configured to operate at intrinsically safe, 24 VDC, 4-20 mA input power.
A temperature sensor. The sensor comprises a wire comprising a resistance temperature detector (RTD) sensing material wrapped around a flexible insulated metal core wire to form an assembly. A first end of the sensing wire is electrically connected to a first end of the core wire. The second end of the core wire provides a first lead, and an insulated lead wire is electrically connected to a second end of the sensing wire to provide a second lead. Shrink tubing encapsulates the assembly.
A thermal dispersion switch/transmitter for determining flow rate and liquid level in a non-contacting apparatus. A special preparation of one or more small spots in the outside surface of the wall of the conduit, standpipe or container enables one or more thermally sensitive elements to reside very close to the fluid on the opposite side of the wall. A temperature sensor is formed of a raster pattern electrical conductor deposited on a thin, electrically insulative, thermally conductive flat chip. One temperature sensor is time-shared and is periodically self heated and functions as the reference as well as the active or heated sensor of the invention. One alternative is to employ two temperature sensors, one being a reference sensor and the other being the active sensor. An alternative embodiment employs the same construction of one or more small, very thin membrane surfaces to which multiple detectors are mounted inside a probe inserted into the conduit. A second alternative embodiment employs the same construction of a very thin, small area spot on the outside of a probe inserted into a conduit or vessel for flow rate, liquid level, or interface sensing.
An improved heated junction thermocouple cable arrangement for use with a nuclear reactor heated junction thermocouple having sensors with an unheated thermocouple, a heated thermocouple, and a heater coil, shares power conductors between multiple heater coils. The thermocouple conductors are separated from the power conductors to eliminate the possibility of interference with the thermocouple conductor signals. The heater coils are ganged in parallel and if one heater coil fails, power is still supplied to the remaining heater coils connected to a pair of power conductors.
