A self-compensated ceramic strain gage for use at elevated temperatures

A ceramic thin film strain gage has been developed for static strain measur ements at temperatures up to 1400 degreesC. These thin film sensors are ide ally suited for in situ strain measurement in harsh environments, such as t hose encountered in the hot sections of gas turbine engines. However, the w ide bandgap semiconductor used as the active strain elements in these devic es also exhibited a large temperature coefficient of resistance (TCR). Thus , to reduce the apparent strain or thermally induced strain in these static strain sensors to an acceptable level, a novel self-compensation scheme wa s demonstrated using thin film platinum resistors placed in series with the active strain element. A mathematical model was developed and design rules were established for the self-compensated circuitry using this approach. C lose agreement between the model and actual static strain results have been achieved using this approach, and reliable static strain measurements have been made over an extended temperature range. (C) 2001 Elsevier Science B. V. All rights reserved.