Dual Resonator MEMS Magnetic Field Gradiometer

Accurate knowledge of the spatial magnetic field distribution is necessary when measuring field gradients. Therefore, a MEMS magnetic field gradiometer is reported, consisting of two identical, but independent laterally oscillating masses on a single chip. The sensor is actuated by Lorentz force and read out by modulation of the light flux passing through stationary and moving arrays of the chip. This optical readout decouples the transducer from the electronic components. Both phase and intensity are recorded which reveals information about the uniformity of the magnetic field. The magnetic flux density is measured simultaneously at two points in space and the field gradient is evaluated locally. The sensor was characterised at ambient pressure by performing frequency and magnitude response measurements with coil and various different permanent magnet arrangements, resulting in a responsivity of 35.67 V/T and detection limit of 3.07 µT/Hz (@ 83 Hz ENBW). The sensor is compact, offers a large dynamic measurement range and can be of low-cost by using conventional MEMS batch fabrication technology.

[1]  Jaume Esteve,et al.  A New Single-Sensor Magnetic Field Gradiometer , 2009 .

[2]  Takahito Ono,et al.  Resonant magnetic sensor using magnetic gradient field formed by permalloy concentrator , 2017, 2017 19th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS).

[3]  Nor Hisham Hamid,et al.  Optical Characterization of Lorentz Force Based CMOS-MEMS Magnetic Field Sensor , 2015, Sensors.

[4]  Jean-Pierre Raskin,et al.  A MEMS-based magnetic field sensor with simple resonant structure and linear electrical response , 2015 .

[5]  Andrew Sunderland,et al.  Optimizing a direct string magnetic gradiometer for geophysical exploration. , 2009, The Review of scientific instruments.

[6]  S. Pourkamali,et al.  Amplitude modulated Lorentz force MEMS magnetometer with picotesla sensitivity , 2016 .

[7]  Héctor Vázquez-Leal,et al.  Recent Advances of MEMS Resonators for Lorentz Force Based Magnetic Field Sensors: Design, Applications and Challenges , 2016, Sensors.

[8]  Franz Keplinger,et al.  Novel MOEMS Lorentz Force Transducer for Magnetic Fields , 2016 .

[9]  D. Horsley,et al.  Dual-resonator MEMS magnetic sensor with differential amplitude modulation , 2017, 2017 19th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS).

[10]  L. Bottura,et al.  FIELD MEASUREMENTS , 2004 .

[11]  Franz Keplinger,et al.  Extremely low resonance frequency MOEMS vibration sensors with sub-pm resolution , 2014, IEEE SENSORS 2014 Proceedings.

[12]  Thilo Sauter,et al.  Robust Precision Position Detection With an Optical MEMS Hybrid Device , 2012, IEEE Transactions on Industrial Electronics.

[13]  Franz Keplinger,et al.  MEMS cantilever based magnetic field gradient sensor , 2017 .

[14]  Toshio Hamada,et al.  Detection of unexploded ordnance (UXO) using marine magnetic gradiometer data , 2005 .

[15]  F. Kohl,et al.  Receiver and amplifier optimization for hybrid MOEMS , 2012, 2012 IEEE Sensors.

[16]  T. Gabrielson.  Mechanical-thermal noise in micromachined acoustic and vibration sensors , 1993 .

[17]  Giacomo Langfelder,et al.  A 3-D Micromechanical Multi-Loop Magnetometer Driven Off-Resonance by an On-Chip Resonator , 2016, Journal of Microelectromechanical Systems.

[18]  Pavel Ripka,et al.  Advances in Magnetic Field Sensors , 2010, IEEE Sensors Journal.

[19]  Sebastian Luber,et al.  Topologically protected vortex structures for low-noise magnetic sensors with high linear range , 2018, Nature Electronics.

[20]  C. Shafai,et al.  Lorentz force based resonant MEMS magnetic-field sensor with optical readout , 2016 .

[21]  N. Simonne,et al.  Temperature influence on Hall effect sensors characteristics , 2012, 2012 20th Telecommunications Forum (TELFOR).

[22]  Thilo Sauter,et al.  MEMS Micro-Wire Magnetic Field Detection Method at CERN , 2016, IEEE Sensors Journal.

[23]  L. Belguerras,et al.  Calibration and non‐orthogonality correction of three‐axis Hall sensors for the monitoring of MRI workers' exposure to static magnetic fields , 2018, Bioelectromagnetics.