Corrosion Enhanced Capacitive Strain Gauge at 370°C

In this paper a silicon carbide passivated capacitive strain sensor is proposed which continuously and accurately measures strain in corrosive ambient and operates up to 370degC in air. The analytical model of this low-mechanical noise, high-resolution and high-gain capacitive SiC coated sensor predicts 45 aF/muepsiv sensitivity, which is in a good agreement with finite element analysis (within 12%) over the intended full-scale range of 1-1000 muepsiv. The gauge is fabricated using silicon-on-insulator and coated with a thin (~60 nm) pinhole-free 3C-SiC layer. The integrity of the passivation layer is tested using a hot KOH bath followed by SEM inspection which shows no defects or damage. A localized-heating, high-temperature testing setup has been built using an infra-red lamp to heat the gauge up to 370degC while maintaining the electronics at significantly reduced temperatures. Experimental results show the strain gauge successfully continues to operate at 370degC.