Method of making resistance thermometer sensors
AssigneeRosemount Engineering Company Limited
InventorKenneth George Rendle
Life of this patent
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Abstract
A resistance thermometer sensor is provided by forming a path of electrically conducting material secured on an insulating base. The path is shaped as a loop having two side-by-side portions. A shorting bar connecting across these portions to short circuit part of the loop is adjusted along their length to trim the ice point resistance of the sensor as required. When suitably adjusted, the shorting bar is fastened in position, for example by welding. In one example, the sensor comprises a bifilar helix of resistance wire wound and secured on a cylindrical former.
Claims10
A method of making a resistance thermometer sensor comprising the steps of providing a base of insulating material and, firmly attaching thereto a path of electrically conducting material with a temperature responsive coefficient of resistance, with at least a part of the length of the path configured as a loop, with two portions in side-by-side relationship and adjusting, along the length of the said portions, the position of a shorting bar connected across said two portions to provide a desired value of ice point resistance for the sensor and then fastening the shorting bar in this position.
A method of manufacturing a resistance thermometer sensor comprising the steps of providing an elongate cylindrical ceramic former, forming a bifilar helix of platinum wire in a U-shaped loop with the arms of the U extended and coated helically around the former in a side-by-side relationship, applying a coating of glaze to the helix and former to secure the wire to the former, the glaze coating being sufficiently thin to leave the outer surface of the wire substantially free from glaze material, bringing the sensor close to another sensor so that they are at substantially the same temperature, said other sensor being previously calibrated and trimmed to have a desired ice point resistance, comparing the resistances of the two sensors, adjusting along the length of said arms of wire, the position of a portion, connected across the arms, of a length of gold wire, until the resistances of the two sensors are substantially equal, thermocompression welding the portion of gold wire in position and then cutting the length of gold wire to leave said portion as a shorting bar connected across said arms.
Dependencies are inferred from the claim text.