Development of temperature-compensated resistance strain gages for use to 700°C

This paper describes the development and evaluation of temperature-compensated resistance strain gages for use to 700°C (1292°F). These gages included single-element gage and double-element gages. The filament of single-element gages was fabricated from specially developed Fe?Cr?Al?V?Ti?Y alloy wire. When bonded to high-temperature Ni-based alloy GH30, the apparent strain from room temperature to 700°C was less than 1800 μm/m. Active grids of double-element gages were fabricated from specially developed Pt?W?Re?Ni alloy wire and Pt-W9.5 wire. The compensating elements were fabricated from Pt?Ir20 alloy wire. When bonded to different high-temperature alloys, by proper adjustment of the ballast resistor in series with the low-resistance Pt?Ir element, apparent strain in the related temperature range was less than 1000 μm/m. Equations to compute the allowable deviation of resistance of compensating element and of ballast resistor for the purpose of attainment of certain measurement accuracy were derived. This paper should be of particular interest to those involved in strain measurement at temperatures to 700°C.