On the Air Buoyancy Effect in MEMS-Based Gravity Sensors for High Resolution Gravity Measurements

• Published in: IEEE sensors journal 2021-10, Vol.21 (20), p.22480-22488
• Main Authors: Xu, Xiaochao, Wang, Qian, Tian, Ji'ao, Yang, Lujia, Fang, Yanyan, Wang, Qiu, Zhao, Chun, Hu, Fangjing, Tu, Liangcheng
• Format: Article
• Language: English
• Subjects: Acceleration measurement; Accelerometers; air buoyancy; Buoyancy; Earth tides; Gravimeters; Gravity; Gravity measurement; gravity sensor; High resolution; high-stability; MEMS devices; Micromechanical devices; Sensors; Temperature measurement; Temperature sensors; Vacuum chambers
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2021.3106667

In this paper, the air buoyancy effect on Micro-Electro-MechanicalSystem (MEMS)-based gravity sensors for high-resolution gravity measurements is investigated. The MEMS gravimeter is operated in an atmospheric environment without any vacuum chamber; thus significantly simplifying the design, implementation and maintenance, and reducing the cost of the instrument. It is experimentally observed that the measured acceleration signal shows a clear correlation with the air buoyancy, and consequently the air pressure. A detailed theoretical model of the air buoyant force acting on the MEMS gravity sensor is proposed, giving a gravity-air pressure coefficient of 501.5 \mu Gal/hPa for the silicon springmass system. After removing the error introduced by the air buoyant force, the MEMS gravity sensor exhibits an ultra-low self-noise floor of 1 \mu {\mathrm {Gal}}/\sqrt{\rm Hz} @1 Hz, as well as an excellent stability, with an Allan deviation of 3 \mu Gal (40 s integration time). The sensor is capable of measuring the Earth tides in a 16-day span. This discovery identified one major error source in high-resolution MEMS gravity sensors operating in atmosphere, which could potentially be useful for the development of future MEMS-based gravimeters.