Rotational Eddy Current Speed Sensor

Abstract

A novel eddy current speed sensor is develope d to measure rotational speed of conductive o bj e ct s. Th e s e nso r co ns ist s o f o n e e xcitation coil and two pick up coils around rotating cylinder or rod. The sensor does not use magnetic y o ke. Fo r t h e a n aly si s a n d e xperimental verification we used 30 mm diameter non-magnetic aluminum and also magnetic solid iron cylinders. The calculated and me asured speed range is until 1200 rpm. 2D analytical method is developed to calculate sensor performance. 2D finite element i s a l so use d for simulations to compare results with 2D analytical method. 3D finite elemen t a n a lys is i s requ ired t o t a k e i nt o a cco u nt significant 3D effects due to the air coils configuration. The experimental results are presented at different steady s t a te s pe eds. Th e calculations results are compared with measurements to validate theoretical models and sensor performance. The eddy current s pe ed se nsor shows high linearity even at low speeds. For ferromagnetic rods we suggest novel double-layer configura t io n: n on-m ag net ic conductive ring or shell on top of the iron rod minimizes the influence of the permeability changes. The main advantage o f t h e n o vel se nsor is that it has neither mechanical nor electrical contact to the rotating rod.

Eddy current speed sensor with magnetic shielding

“…It is shown that eddy current speed sensor sensitivity is highly dependent on the moving part material properties. Conductivity of aluminum and iron moving part and relat iv e permeability of iron moving part could change ed dy cu rren t speed sensor outputs [13]. Compensating moving part material properties on the eddy current speed sensor output is a challenging issue and it must be addressed.…”

“…The presented models in [5] - [11] had only nonmagnetic aluminum moving part, which is simpler for analysis but not practical for industry in comparison with solid iron moving part. The authors analyzed and tested similar eddy current speed sensors for solid iron rod lin ear [12] an d rotational configuration [13] without magnetic yoke and shield. These sensors suffered from sensitivity to magnetic interference and also to the presence of ferromagnetic materials from their vicinity.…”

Inductive Position and Speed Sensors

“…The limitation of this solution is again the temperature stability of the source field. An AC-excited rotational eddy current speed sensor consists of three stationary coils around the conductive shaft [24]. The sensor structure and magnetic field distribution are shown in Figure 7, while Figure 8 shows the prototype wound on a 3D printed bobbin.…”

A Novel Eddy Current Speed Sensor With a Ferrite E-Core

“…The authors recently developed different types of eddy current speed sensor with iron and aluminum moving parts for rotating and translational motions [Mirzaei 2019a, Mirzaei 2019b, Mirzaei 2020aand Mirzaei 2020b]. These sensors were designed and analyzed both with the air core and magnetic yoke.…”