Analysis on Gas Film Damping of Capacitive Micro Accelerometers

Based on the rarefied gas dynamics theory and the squeeze film Reynolds equation amended with slip flow boundary condition, the gas film damping effect on the sensitive proof mass, moving along its axial direction, is analyzed for capacitive micro accelerometers. Simplified analysis solutions are obtained for damping force and damping coefficient. It shows that gas film damping force has relations not only with the accelerometer dimensions and velocity of the sensitive proof mass, but also with the factors, such as solid wall material, surface roughness, smooth finish, and so on. Three methods have been proposed to decrease the gas film damping of capacitive micro accelerometers through sample analysis. Finally, it is pointed out that accomodation coefficient is an key factor for gas film damping, especially for squeezed film damping.