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A MEMS Variable Reluctance Sensor for Contactless Detection of a Ferrous Rotating Target.

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Summary

This study introduces a microelectromechanical systems (MEMS) variable reluctance induction sensor for noncontact detection of rotating ferromagnetic targets. The MEMS sensor reliably measures rotational speed, proximity, and shape, demonstrating potential for compact motion sensing applications.

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micromachined coilspeed and proximity detectionvariable reluctance sensor

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Area of Science:

  • Sensor Technology
  • Microelectromechanical Systems (MEMS)

Background:

  • Variable reluctance sensors are crucial for robust, contactless motion detection in challenging environments.
  • Existing sensors often face limitations in space-constrained or harsh conditions.

Purpose of the Study:

  • To present a novel MEMS-based variable reluctance induction sensor for characterizing rotating ferromagnetic targets.
  • To investigate the sensor's capability for noncontact measurement of rotational speed, proximity, and target geometry.

Main Methods:

  • Development of a MEMS sensor featuring a micromachined planar micro-coil and an external permanent magnet.
  • Utilized lumped-element modeling and finite-element magnetostatic simulations to analyze sensor operation.
  • Experimental validation using rotating drill bits and a high-gain amplification circuit.

Main Results:

  • The sensor generates a voltage signal modulated by the target's rotation, encoding speed, proximity, and shape information.
  • Demonstrated reliable detection up to 1500 rpm for targets as small as 5 mm in diameter and at distances up to 8 mm.
  • Measured voltage waveforms varied consistently with target geometry, proximity, and speed.

Conclusions:

  • MEMS variable reluctance induction sensors offer a promising solution for compact and noncontact speed sensing.
  • The developed sensor technology shows potential for effective target shape detection in various applications.