Monolithic accelerometer

An investigation of the monolithic accelerometer was carried out to evaluate its potential for inertial navigation applications. The work included analysis and design studies, construction of a breadboard accelerometer, and laboratory testing. The approach used a suspension of two single-crystal silicon diaphragms joined to a frame of silicon or pyrex. Gold diffusion, thermoelectric, and optical contact bonds were used in the assembly. A differential capacitance pickoff was used to sense acceleration. Digital readout was obtained from the differential output of two oscillators, each slaved in frequency to its associated pickoff capacitor. Tests were conducted for bias, scale factor, scale factor linearity, and threshold. The tests showed that performance was limited by milli-g variations in bias and scale factor. The instabilities are attributed to residual stresses in the diaphragm suspension, resulting from the high-temperature bonding process. Recommendations are given for extending the concept to improved performance.