# Adaptive Algorithm for Fast 3D Characterization of Magnetic Sensors
## 4 Discussion
The conducted experiments were performed only with one sensor, which does not guarantee comparable results with other sensors. The system parametrization (e.g., EQ design) also incorporated a priori knowledge on this investigated sensor type. Further work could investigate the applicability of our findings to magnetic sensors in general. This would include a change of the EQ design to equalize the coil system in the range of the expected sensor bandwidth. Furthermore, other sensor technologies might need adapted parameter sets, e.g., with adjusted filter lengths for a different impulse response behavior, and additional readout electronics to match the devices' dynamic ranges to the operational ranges of the ADC and DAC components. Otherwise, different converters might also be employed. Generally, the proposed estimation is only expected to cover linear sensor behavior and not possible nonlinear operation points due to the linear nature of the FIR structure adapted by the NLMS algorithm. To estimate nonlinear behavior, a different adaptation structure of, e.g., a Volterra series would be necessary. The proposed equalization is limited in accordance with the generating coils and cross talk between coils cannot be ruled out entirely. Thus, there might be a deviation between the calculated, ideal excitation field direction and the field the sensor is practically exposed to. As the setup actively generates a field, it is not in a shielded environment and is thus limited to uses with magnetic sensors working in unshielded conditions. This relates to the additional impact of the potential influence of external fields, e.g., Earth's magnetic field or stray fields by nearby equipment, on the sensor's output. We do not assume a large impact due to the significantly higher strength of the applied fields. Further research is needed to assess possibly introduced low-frequency drifts and similar possible implications. However, this is beyond the scope of this proof-of-principle study. At the current stage, the resulting impulse and derived frequency response estimates give a qualitative insight into the sensor behavior. They do not contain explicit information about the sensor sensitivity as the goal for this contribution is focused on a qualitative (not quantitative) description. To convert this into absolute sensitivity measurements, a reference sensor with known sensitivity could be used with identical field actuation in one direction. From such knowledge of the absolute field, the arbitrary units could be related to quantitative sensitivity measures. A different approach could be the deviation of theoretical field strengths based on the Helmholtz coil equations (cf. (2)) with measured currents through the coils. The runtime of the multidimensional estimations of the algorithm and the estimated quality (given by the system distance) of the respective results depend on the chosen parameters. More investigated field directions and a smaller target system distance can lead to longer runtimes, with a possible gain of higher-quality results. A trade-off must be made depending on the individual objectives and overall conditions of a measurement. A quantitative analysis of the influence of different algorithm parameters could be studied with a potential investigation of optimization procedures for ideal parameter combinations for distinct objectives.