DocumentCode :
2945973
Title :
MEMS heterodyne AMF detection with capacitive sensing
Author :
Stifter, Michael ; Sauter, T. ; Hortschitz, Wilfried ; Keplinger, F. ; Steiner, H.
Author_Institution :
Inst. for Integrated Sensor Syst., Wiener Neustadt, Austria
fYear :
2012
fDate :
28-31 Oct. 2012
Firstpage :
1
Lastpage :
4
Abstract :
A Lorentz-force actuated cantilever used as a magnetometer detecting alternating magnetic fields (AMF) is described. The device consists of a U-shaped single-crystal silicon cantilever manufactured in SOI technology. This micromachined cantilever features a length of 2mm, a base width of 90μm, and a thickness of 20μm, whereat the two 2mm cantilevers are hold together by a 1.5mm long bar at the free moving ends. The cantilever is placed in a vacuum chamber surrounded by a pair of coils configured as Helmholtz coil which generates the alternating magnetic field. The test structures are harmonically excited by the Lorentz force acting on the gold lead at the top surface of the cantilever carrying an alternating current. In the presence of a sinusoidal magnetic flux density, the resulting Lorentz force contains two alternating terms including the sum and difference of current and field frequencies. Therefore, the resonating cantilever is used as mixer in a heterodyne detector for alternating magnetic fields with variable frequency. Resonant excitation only occurs if one of these frequencies is close to a mechanical resonance that satisfies the selection rule imposed by the field configuration. In the experiments, emphasis is laid on the investigation of the first symmetric and first antisymmetric vibration mode, where the amplitude of the vibration is proportional to the exciting vector component of the magnetic field. For this work the harmonic deflection of the cantilever was measured with a capacitive readout system and additionally, with a laser-Doppler vibrometer. By changing the drive current, the operating range of the magnetometer can be varied from a few μT up to 1mT, whereas the sensitivity remains constant with an uncertainty of less than one percent, valid for both vibration modes. This operation principle of the prototype allows a further miniaturization leading to a spatial resolution of the magnetic field detection determined by t- e size of the cantilever.
Keywords :
Doppler measurement; cantilevers; capacitive sensors; digital readout; harmonics suppression; heterodyne detection; magnetic field measurement; magnetic flux; magnetometers; measurement by laser beam; measurement uncertainty; micromachining; microsensors; silicon-on-insulator; vibration measurement; Helmholtz coil; Lorentz force actuated cantilever; MEMS heterodyne AMF detection; SOI technology; alternating magnetic field; antisymmetric vibration mode; capacitive readout system; capacitive sensing; drive current; harmonic deflection measurement; laser Doppler vibrometer; magnetic field detection; magnetometer; measurement uncertainty; mechanical resonance; micromachined cantilever; mixer; resonant excitation; resonating cantilever; sinusoidal magnetic flux density; size 1.5 mm; size 2 mm; size 20 mum; size 90 mum; spatial resolution; symmetric vibration mode; vacuum chamber; Magnetic resonance; Magnetoacoustic effects; Magnetomechanical effects; Magnetometers; Micromechanical devices; Vibrations;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Sensors, 2012 IEEE
Conference_Location :
Taipei
ISSN :
1930-0395
Print_ISBN :
978-1-4577-1766-6
Electronic_ISBN :
1930-0395
Type :
conf
DOI :
10.1109/ICSENS.2012.6411171
Filename :
6411171
Link To Document :
بازگشت