Portable signal conditioning system of a MEMS magnetic field sensor for industrial applications

Abstract

We present a portable signal conditioning system of a micromachined magnetic field sensor. This system, implemented on a printed circuit board, includes a new algorithm for two sinusoidal signal generators, which bias the magnetic field sensor. This algorithm uses the direct digital synthesis technique for two embedded peripheral interface microcontrollers. The magnetic field sensor consists of a resonant silicon structure (600 µm × 700 µm × 5 µm), an aluminum loop (1 µm thickness), and a Wheatstone bridge of four type-p piezoresistors. The two signal generators have a frequency stability of ±100 ppm and a resolution of 1 Hz. With this system, the magnetic field sensor has a linear approximately response in voltage mode as well as experimental sensitivity and resolution of 0.32 V Tź1 and 35 nT at atmospheric pressure, respectively. A virtual instrument is designed to visualize the output voltage of the magnetic field sensor. The signal conditioning system of the sensor could be used as industrial portable equipment to detect residual magnetic fields of ferromagnetic materials.