## 2 Materials and Methods
### Measurement Chain  
The measuring workstation is designed as a modular system intended to measure the magnetic properties of long open-ended samples. The output of the measurement, using workstation algorithms, is given as the typical magnetic hysteresis curve, the reconstruction process of which consists of four consecutive parts--magnetization of the investigated  
Figure 2: Magnetic dipole moment represented by a pole model using hypothetical magnetic point charges: distribution of the magnetic stray field components at the measurement point. sample, measurement of the stray magnetic field, pre-processing and post-processing of the measured value, and a real-time graphical representation of processed data. These are implemented by individual functional modules forming a measurement chain of the measuring workstation, which consists of the following hardware and software equipment:  
* Relax-type fluxgate magnetometer VEMA 04 developed at the Department of Aviation Technical Studies at the Faculty of Aeronautics of the Technical University of Kosice. The total range and sensitivity of the VEMA magnetometer are up to \(\pm\)50,000 nT and 3.5 nT, respectively. The sample rate of a used model is about 500 Hz [47]. * Measuring stand with integrated magnetizing (excitation) and compensation coils, between which a sensing probe holder is located. The total length and radius of the coils are 290 mm and 50 mm, respectively. Both coils can generate a relatively identical but opposite magnetic field with a magnitude of 3896.55 A/m per ampere at their midpoint, from which the magnetic field drop is at a distance of 50 mm less than 2% (Note that the magnetized sample should be during the measurement process constantly exposed to a homogenous magnetic field). A skeleton of the measuring stand was made by an additive manufacturing process based on fused depositing modeling technology. * Evaluation board with high precision 20-bit AD5791 digital to analog converter enables to generate bipolar supply up to \(\pm\)15 V.
* Arduino Mega 2560 microcontroller unit (MCU) based on the ATmega2560 microprocessor with an integrated program intended for control and configuration of the D/A controller. * A personal computer with application software [48] that defines and controls the measuring process, statistically processes the measured data in order to reduce measurement uncertainties, calculates the magnetization characteristics according to the integrated mathematical apparatus, and provides its real-time visualization using a graphical user interface. * Constant-current power supply with input ranges up to \(\pm\)3 V.  
The start of the measuring process is initiated by the application software after the measuring workstation is configured. During the measurement, data in the form of binary digits, which corresponds to a desired current level, are continuously emitted by the application software and transferred to an input of the microcontroller unit. Once the microcontroller unit processes the acquired data, communication with the D/A converter is initiated. As a result, the D/A converter can receive digital information about the desired current value, which is subsequently converted into an analog voltage signal necessary for further processing. From this point, the voltage signal needs to be transformed to the corresponding current level since the excitation magnetic field is the function of the current, not the voltage. Therefore, the current power supply is included in the measurement chain to generate the direct current with a value equivalent to the magnitude of the voltage signal from the D/A converter output. The generated current then supplies the compensation and excitation coils. Within the excitation coil, the investigated ferromagnetic core is placed. As the current runs through both coils, the excitation magnetic field is produced, in consequence of which the stray magnetic field arises around the magnetized core.