A novel micromachined accelerometer without proof mass, based on the buoyancy of a heated fluid around a polysilicon heater, has previously been developed and reported. Significant features of this class of accelerometer include low cost and the combination of high sensitivity with high survivability. However, one of its big disadvantages is thermal drift: the sensitivity changes rapidly as the ambient temperature changes. A recent numerical and experimental study has shown that the sensitivity of the convective accelerometer is a function of the Rayleigh number of the working fluid. Using this criterion, a few liquids were selected as potential working fluids to improve the sensitivity of the accelerometer. The CFD program ‘FLOTRAN’ was used to model accelerometer performance using each of these fluids. Based on FLOTRAN modeling, some fluids were selected for experimental investigation. The thermal drift of the accelerometer using different working fluids was documented and the reasons for this thermal drift were discovered. Based on this observation, some possible solutions were proposed to reduce or eliminate the thermal drift.

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