The model 40366 accelerometer is a variable capacitance, silicon MEMS device designed to meet the demanding requirements for use in implantable devices, such as rate responsive heart pacemakers and defibrillators. High reliability, repeatability, and a very small package size are key criteria for acceleration sensors in these critical quality-of-life medical applications. Hermetically sealed with shear bond strength of 1.0 kg, the model 40366 delivers repeatability of less than 0.035 pF in an SMT footprint of only 2.05 × 2.90 mm configured as a three-terminal half-bridge. Acceleration through the oblate axis causes one capacitor to increase in value as the other decreases, while air damping creates an inertial system that is over damped.