LCSR Method to Verify the Attachment of Temperature Sensors and Strain Gauges to Solid Material

Abstract

Resistance Temperature Detectors (RTDs) and thermocouples in some applications are attached to solid surfaces or imbedded in solid material for measurement of temperature of the solid material or the material within the solid boundary. For example, thermocouples are imbedded in the nozzle of Solid Rocket Motors (SRMs) to measure the temperature of the lining material of the nozzle. These thermocouples must remain intact during SRM firing tests to provide an accurate temperature profile especially under transient temperature conditions. This paper describes the Loop Current Step Response (LCSR) method that was developed for this and a number of other applications. This method is based on heating the thermocouple with an electric current to characterize the heat transfer condition around the measuring tip of the thermocouple. The same principle can also be used to verify the attachment of RTDs and strain gauges to solid surfaces. This is important in such applications as fuel leak detection in space shuttle engines, measurement of fluid temperatures within pressure sensing lines in nuclear power plants, and diagnostics of problems in instrumentation which involve strain gauges.