Sensors & Hardware
How Magnetometers Work and the Key Products — Bosch, ST, Honeywell
The magnetometer, which senses the direction of Earth's magnetic field to derive heading, is the one sensor that keeps returning an absolute-direction external reference as long as it has power — from a smartphone's electronic compass, to yaw-angle correction on a drone, to attitude control on a CubeSat. This article lays out the four underlying physical principles — the Hall effect, AMR, GMR, and fluxgate — compares real chip specs across the Bosch BMM150, STMicroelectronics LIS3MDL, and Honeywell HMC5883L, covers hard-iron/soft-iron error and its calibration, AHRS sensor fusion with an IMU, and the technology's history from ore prospecting through WWII submarine hunting and lunar exploration to today's CubeSat attitude control.