An new eddy current based magnetic position encoder structure is proposed and
studied in this thesis. The encoder is composed of one read head and one scale with
metal plates placed periodically on a substrate. The read head contains one emitter
and two receiver pairs which are all rectangular planar coils. The electromagnetic
coupling between the emitter and receivers were affected by the relative position of
the scale. A system level analytical model of the proposed encoder structure has
been derived, from which three different encoder signals forms were generated.
An amplification and synchronous demodulation circuit has been designed and
fabricated. The circuit board was used successfully to process the encoder output
signals in the measurement.
Four PCB encoder prototypes were fabricated. These encoder structures were
studied using the ANSYS MaxwellTM software package. The simulated and measured
results were compared. The best accuracy performance of the PCB encoder is -15 μm to 15 μm from the simulation results and -35 μm to 25 μm from the corresponding measurement.
An alternative manufacturing process of the magnetic encoder based on multilayer
Low Temperature Co-fired Ceramic (LTCC) technology has also been presented. The
fabrication process of the LTCC encoder and equipment used were described. Two
different methods were used to characterise the LTCC encoder with good agreement
between all approaches attempted. The best accuracy performance of the LTCC encoder was -30 μm to 25 μm and after lookup table correction the improved accuracy ranged from -10 μm to 10 μm
