High-accuracy teslameter with thin high-resolution three-axis Hall probe

Abstract

The new digital teslameter system (also called Gaussmeter) incorporates a 3-axis Hall probe, analog electronics based on the spinning-current technique, 24-bit analog-to-digital converter, computer, and 7-digit touch-screen display. The Hall probe is a single silicon chip with monolithically integrated horizontal and vertical Hall magnetic sensors and a temperature sensor. The Hall sensor chip is encapsulated in a robust ceramic package, a version of which is only 250 μm thick. The spinning-current eliminates most of the Hall probe offset, low-frequency noise, and the planar Hall voltage. The errors due to the Hall element non-linearity and the variations in the probe electronics temperatures are eliminated by a calibration procedure based on a three-variable second-order polynomial. The errors due to the angular errors of the Hall probe are eliminated by a calibration of the sensitivity tensor of the probe. These new developments resulted in a teslameter that can measure magnetic field vectors from about 1 μT to 30 T, with the spatial resolution 100 μm, magnetic resolution ±2 ppm of the range, the accuracy ±0.0001% of reading +0.001% of range, temperature coefficient less than 5 ppm/°C, and angular errors less than 0.1 deg.