Abstract

In this talk, a novel micromachined magnetic field sensor was designed and fabricated. The sensor operation is based on fundamental electromagnetic laws to produce a mechanical stress proportional to the strength of the present magnetic field. The exerted stress modifies the resonant frequency of an electrostatic resonator, and hence, the sensor output is a frequency shift proportional to the magnitude and direction of the present field. Operation of the sensor involves interaction of multiple physical domains including: magnetostatic, electrostatic, static, dynamic, and electro-thermo-mechanical. A comprehensive model of the sensor behavior is derived and verified by finite element simulations and experiments. The sensor was fabricated in a standard bulk micromachining process without the need for any additional processing steps. Custom signal processing electronics were designed and used to analyze the sensor data. A novel configuration is proposed for employing the resonator in an oscillator loop as well as the circuitry for measuring the frequency shifts. Experimental results for the measurements of magnetic fields and performance of the electronic circuitry are also presented. The noise behavior of the sensor is also investigated and the minimum detectable signal for each device is found. The measured resolution of the fabricated sensors in self-oscillating configuration using off-the shelf discrete electronics is about 77uT. A linear response to a wide range of magnetic fields makes this design suitable for applications where large fields need to be measured with high resolution