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Measuring system for the visualization of magnetic fields

Johannes Wöß

The measurement of magnetic fields is used in a wide range of applications, for example in nondestructive evaluation of metallic structures or in detecting currents (contactless).
The aim of this master thesis is to measure the z-component of the magnetic field over an area of a few centimeters in each direction. A good compromise between accuracy and speed will be found. Additionally, a low-cost design has been sought.
Beginning with the NVE magnetometer AA002-02 that was placed on its own "sensor-board", a "measuring-board" was then designed and produced. This board is connected to the analog ports of an ATxMega32a4 controller board. Together, these three components are responsible for ensuring that digitised measurements can be send to a computer.
In order to measure the z-component of the magnetic field on an area, the sensor must be moved over it. The first movement was accomplished with the aid of a brushless DC motor utilized from an old hard disk drive, an eccentric and a rocker arm on which end the sensor board is attached. The sensor oscillates every 200 ms over a circle segment with a secant length of 120 mm.
In order to measure an area, this circle segment is moved with a linear axis.
This consists of a linear guide NW27 from Igus and a stepper motor with pinion gear, spur gear and rack.
A board connected to the digital ports of the controller board was made for the electronics of the entire sequence of movements.
The ATxMega32a4 controller board has been programmed so that various control commands can be sent from a PC, with the measured values then transmitted back to the PC.
A Matlab GUI was written for the computer which controls the measuring system and plots the measurement data.

Figure 1: measuring system

Figure 1: measuring system

Keywords: GMR, magnetometer, magnetic field measurement, ATXMega, BLDC motor, ...

October 14, 2014