Design of a Multiturn RVDT with Flat-Helix Coils

Measuring angular displacement is a common demand for many industries. In this setting, sensing technologies that minimize or eliminate measurement friction are preferable in such environments since the device’s robustness to mechanical wear reduces the need for maintenance and its costs. That includes rotary variable differential transformers (RVDTs), which stand out for their recognized good resolution and reliability. However, despite measurement quality and vast applicability, these devices present some significant drawbacks regarding their size and working range limitations. In this context, this work investigates the feasibility of a novel RVDT design. We use flat-helix coils and an amorphous alloy core as the sensor, providing a piece-wise linear angular displacement measurement without restricting rotor movement. By performing experiments with the developed prototype, it was possible to analyze, qualitatively and quantitatively, instrumentation aspects related to the proposed arrangement. Besides the capacity to perform a multiturn measurement, an average linearity coefficient of 98.75% and a mean standard deviation between experiments of approximately 1.7% were obtained, reinforcing measurement uniformity and linearity even with handmade windings and experimental setup limitations.