PdCr based high temperature static strain gage

The program at NASA Lewis Research Center to develop a high temperature static strain gage system for the hypersonic vehicle and turbine engine research has emphasized a palladium-13 wt pct chromium (PdCr) alloy. Gages made from this alloy are being developed in both fine wire and thin film form. The wire gage system had platinum wire as a temperature compensator and was coated with a special alumina and zirconia mixture overcoat. This PdCr compensated wire gage responded linearly to the imposed strain to at least 1000 microstrain. The apparent strain varied within 300 microstrain from room temperature to 800 C with a reproducibility within 50 microstrain between thermal cycles to 800 C. The sputtered thin film PdCr strain gage, whose size was 8 x 8 mm and 10 microns thick, has demonstrated the possibility of extending the use of the PdCr strain gage to a temperature of approximately 1000 C.