A high-sensitivity MEMS gravimeter with a large dynamic range

Abstract

Precise measurement of variations in the local gravitational acceleration is valuable for natural hazard forecasting, prospecting, and geophysical studies. Common issues of the present gravimetry technologies include their high cost, high mass, and large volume, which can potentially be solved by micro-electromechanical-system (MEMS) technology. However, the reported MEMS gravimeter does not have a high sensitivity and a large dynamic range comparable with those of the present commercial gravimeters, lowering its practicability and ruling out worldwide deployment. In this paper, we introduce a more practical MEMS gravimeter that has a higher sensitivity of 8 μGal/√Hz and a larger dynamic range of 8000 mGal by using an advanced suspension design and a customized optical displacement transducer. The proposed MEMS gravimeter has performed the co-site earth tides measurement with a commercial superconducting gravimeter GWR iGrav with the results showing a correlation coefficient of 0.91.

Ultralow Mechanical Damping with Meissner-Levitated Ferromagnetic Microparticles

“…A second one is represented by mechanical sensing of weak signals. Well known examples are force microscopy [5], force-detected single spins [6], detection of small masses at molecular level [7], ultrasensitive accelerometry [8] and gravimetry [9,10], magnetometry [11] and tests of wavefunction collapse models [12].…”

Micromachined Accelerometers with Sub-µg/√Hz Noise Floor: A Review

“…Boom and Kamp et al [16] 2 ng/ √ Hz (at 28.1 Hz) -3-28.1 Hz #+M iddlemiss et al [18] 8 ng/ √ Hz (at 1 Hz) -2.31 Hz #+Ẑ hang et al [22] 51.8 ng/ √ Hz (at 1 Hz) -158 Hz #T ang et al [24] 8 ng/ √ Hz (at 1 Hz) +8 mg 0.5-3 Hz #+P ike et al [31] 0.25 ng/ √ Hz (at 0.1-10 Hz) -6 Hz + Wu et al [39] 10-50 ng/ √ Hz (at 1 Hz) ±1.4 g 13.2 Hz + Edalatfar et al [44] 350 ng/ √ Hz (at 1-5 kHz) 135 dB 4500 Hz + Yazdi and Najafi [45] 160 ng/ √ Hz -<1000 Hz + Aaltonen et al [9] 300 ng/ √ Hz (at 30 Hz) ±1.5 g 300 Hz +X u et al [11] 200 ng/…”

“…Tang et al [23,24] (2019) at Huazhong University of Science and Technology developed a MEMS accelerometer with a novel quasi-zero stiffness suspension, as shown in Figure 5. In this design, the negative spring constant of a curved bi-stable spring cancelled the positive spring constant of two folded springs, producing a low overall spring constant and thus a low resonant frequency of 3 Hz.…”

“…However, theoretically, levitated MEMS accelerometers can have a spring constant lower than any mechanical suspension system, making it a very promising suspension scheme to improve the resolution of such sensors below a 1 µg/ √ Hz noise floor. Most MEMS accelerometers with a noise floor lower than or equal to 10 ng/ √ Hz mainly achieved this by improving the mechanical design, most notably using a geometric antispring suspension (GAS) [16,18,24] or by simply increasing the proof mass weight [31,39,46,49,50]. Five MEMS accelerometers reached such a low noise floor used optical sensing schemes, including optical micro-grating sensing [87], morphology-dependent optical resonance sensing [74], optical FP sensing [81] or optical shadow sensor sensing [18,24].…”

“…Most MEMS accelerometers with a noise floor lower than or equal to 10 ng/ √ Hz mainly achieved this by improving the mechanical design, most notably using a geometric antispring suspension (GAS) [16,18,24] or by simply increasing the proof mass weight [31,39,46,49,50]. Five MEMS accelerometers reached such a low noise floor used optical sensing schemes, including optical micro-grating sensing [87], morphology-dependent optical resonance sensing [74], optical FP sensing [81] or optical shadow sensor sensing [18,24]. Only one MEMS accelerometer reached such a low noise floor using an electrochemical sensing scheme [122].…”