Integrated system development of a MEMS Pendulum Gravimeter

<p>Gravimetry has many valuable applications from volcanology to water resource management; being a method able to infer density variations beneath the ground. Therefore, it can be used to provide insight into subsurface processes such as those related to the hydrothermal and magmatic systems of volcanoes.&#160;Existing gravimeters are costly and heavy, but this is changing with the utilisation of a technology most notably used in mobile phone accelerometers: MEMS &#8211; (Microelectromechanical-systems). A team at the University of Glasgow has already developed a MEMS relative gravimeter. A second generation of the MEMS sensor is now being designed and fabricated in the form of a semi-absolute pendulum gravimeter.&#160;Pendulum gravimetry was one of the prominent methods for gravimetric measurements up until the 20^th century. However, scientists and engineers reached the limit of fabrication tolerances and readout accuracy approximately 100 years ago. With micro/nanofabrication and modern electronics techniques, it is now feasible to create a competitive pendulum gravimeter again.&#160;The research presented here will focus on the testing of an integrated semi-absolute gravimeter system. This encompasses a MEMS pendulum device that&#8217;s encapsulated within a thermal enclosure and stationed on a horizontal isolation platform. Micro/nanofabrication processes have been used to create the pendulum device. An optical shadow-sensor has been developed to monitor its oscillation. This optical readout can provide measurements to sub-nanometre precision. Data collected from laboratory testing will be presented to demonstrating the progression being made towards a prototype field device.&#160;This data will include measurements of the influence of tilt-sensitivity and the seismic and shadow sensor noise floors. Altitude tests of the free-air effect will also be presented to demonstrate the current sensitivity of the device. If semi-absolute values of gravity can be measured, then instrumental drift concerns are reduced. With the high cost of current absolute devices then this device could provide the technological advancement required to realise large scale array gravimetry.</p> <div> <div> <div>&#160;</div> </div> <div> <div>&#160;</div> </div> <div> <div>&#160;</div> </div> </div>