A Linear Capacitive Gravimeter with Pseudo-Differential Electrodes Capable of Measuring Earth Tides

This paper discusses a new design for a new pseudo-differential electrode arrangement that is employed to develop a highly sensitive gravimeter. Unlike the earlier reported micromachined gravimeters, this device utilizes a set of linear springs. A dicing-free fabrication process with a high-yield is developed that allows for the retention of a portion of the handle wafer letting the device have a large proofmass in a relatively small chip area of 1cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. The gravimeter has undergone extensive characterization and has a sensitivity of 86pF/g when measuring 1g, a resonance frequency of 445Hz, and a noise floor of better than $350ng/\sqrt {Hz} $. The device was used to track the variations in gravitational forces over a period of two weeks and could detect the effect of earth tides after removing the temperature interferences.