Design of a portable, two dimensional magnetometer, using 2 dimensional quantum Hall effect sensor array, optimised for low magnetic field applications

The use of Hall effect sensors is always accompanied by the problem of the large amount of unwanted offset voltage. A tremendous effort has taken place in the last decades to reduce the offset voltage as much as possible. This work reports the application of the technique of the full mode of spinning current-and-averaging technique for offset reduction to enhance the performance of a low magnetic field (<1 μT), 2D AlGaAs-InGaAs-GaAs Hall sensor, which was designed and optimised at UMIST. The design requirements of a portable, LabVIEW-based, low field magnetometer based on a new programmable switching network (PSN), and data acquisition system (DAQ), that can perform different modes of spinning current-and-averaging techniques for offset reduction, with the principle of reverse magnetic field reciprocity being applicable if required, is presented. Experimental results of a full mode of the technique showed the lowest offset voltage reported so far in semiconductor Hall devices, with an average value of the offset magnetic field of 5 μT; this is about half of the best reported so far. We also present experimental results of the offset dependence on both the bias frequency and the preamplifier circuitry, which led to the careful selection of the system parameters for the lowest possible offset voltage. The proposed design of the (PSN) and the (DAQ) is easily modifiable to acquire a magnetic signal from a 2D quantum Hall effect sensor array.