The Model 40366 from Endevco Corp., San Juan Capistrano, CA, is a variable capacitance silicon MEMS device designed for use in implantable devices such as rate-responsive heart pacemakers and defibrillators. The sensor is hermetically sealed with a shear bond strength of 1 kg and has <0.035 pF repeatability, 40 Hz frequency response, <1% linearity, <1% transverse sensitivity, and over-range stops to eliminate electrostatic sticking when the accelerometer is over ranged. The SMT footprint is 2.05 by 2.90 mm. The sensor is configured as a 3-terminal half-bridge; acceleration through the oblate axis causes one capacitor to increase in value as the other decreases, and air damping creates an over-damped inertial system.
Implantable Accelerometer from Endevco