3-axis sensing

VTI's three axis accelerometer concept offers a single element solution to measure the low-g acceleration, the magnitude and the direction accurately. The three axis sensor element takes advantage of proven VTI single axis accelerometer element technology by utilising bulk micromachined inertial masses and the capacitive measurement principle.

The sensor design is based on multiple proof masses suspended asymmetrically with torsion springs attached close to the surface of the silicon wafer. An inertial mass with a relatively high thickness attached in this way is sensitive in vertical and horizontal directions of the wafer.

The resultant sensing direction depends on the location of the proof mass center of gravity with respect to the suspension points. The horizontal surfaces of the mass and metal electrodes on the capping wafers on both sides of the mass form a differential capacitor system. When the mass is excited, it will rotate. The movement changes the electrode distances and thus the capacitances.

The three orthogonal components of the acceleration vector can be calculated as linear combinations of the position signals of the proof mass-electrode systems. The concept enables very similar linear responses in all three measurement axes.