An accelerometer incorporating a laser microencoder for a wide measurable range

A small, highly accurate accelerometer that can measure a wide range of accelerations has been developed. The accelerometer incorporates an optical linear microencoder that measures displacement relative to a long, linear grating scale attached to a movable seismic mass with a restoring force. As a result, there is virtually no limit on the measurable range. A wire-cut two-parallel-plate cantilever and a silicon stage suspended by a monolithically integrated spring have been investigated as seismic masses. The accelerometer developed has a high design freedom in terms of both resolution and measurement range. By incorporating a microencoder, we achieved a resolution of 6.4 μg for a range of 0-1.8 g with the parallel two-plate cantilever, and 0.45 mg for a range of 0-1 g with the Si stage. If cut-filtering at more than 2 kHz is used, the resolution is improved further by one order of magnitude for both types of seismic mass.