A novel eddy current speed sensor is developed to measure the rotational speed of conductive objects. The sensor consists of one excitation coil and two pick-up coils around a rotating cylinder or rod. The sensor does not use magnetic yoke. For the analysis and experimental verification, we used 30 mm diameter non-magnetic aluminum and also magnetic solid iron cylinders. The calculated and measured speed ranges are up to 1200 r/min. A 2-D analytical method is developed to calculate sensor performance. A 2-D finite element is also used for simulations to compare results with the 2-D analytical method. A 3-D finite-element analysis is required to take into account significant 3-D effects due to the air coil configuration. The experimental results are presented at different steady-state speeds. The calculation results are compared with measurements to validate theoretical models and sensor performance. The eddy current speed sensor shows high linearity even at low speeds. For ferromagnetic rods, we suggest a novel double-layer configuration: non-magnetic conductive ring or shell on top of the iron rod minimizes the influence of the permeability changes. The main advantage of the novel sensor is that it has neither mechanical nor electrical contact to the rotating rod.

This letter presents a novel speed sensor based on the motion-induced eddy currents in conductive moving parts. The magnetic yoke is an E-shaped Ferrite core. The excitation coil is on the centre leg of the E-core, and two antiserially connected pick-up coils are on the side legs. Solid iron and aluminum materials are used for the moving part in the simulations and in the measurements. 2D and 3D finite element methods are used for a detailed analysis and for the parametric calculations of the eddy current speed sensor. Despite its simple structure, the proposed eddy current speed sensor shows high linearity. The analysis and the measurements are performed at various speeds and excitation frequencies for an evaluation of the performance of the eddy current speed sensor. The minimum linearity error is less than 0.5%.

This paper presents a novel structure of an eddy current sensor for the measurement of rotational speed. The sensor has a perpendicular configuration of the excitation coil and the pick-up coil. Its maximum nonlinearity error is 0.15%. The excitation coils and the pick-up coils are divided into two identical parts with a coil span of 180 degrees. Various solid iron cylinders with different electrical and magnetic characteristics, one solid aluminum cylinder and one solid copper cylinder, were used as the rotating shafts. A novel 2D analytical method in cylindrical coordinates has been developed for fast parametric analysis of this sensor. 2D and 3D time-stepping finite-element methods that take into consideration the shaft motion are used for a performance analysis of the eddy current sensor. The measurements of the speed sensor are performed at various frequencies and speeds and are compared with the calculations for detailed analysis. The effects of the rotating shaft materials are evaluated both in the measurements and in the calculations.

A novel position sensor for pneumatic and hydraulic cylinder applications is presented in this paper. The solid iron core conical in shape surrounded by axisymmetric coils is an essential part of the proposed position sensor. The axisymmetric coils are used for excitation and voltage measurements. The conical solid iron core is annealed to homogenize the magnetic properties and to increase the permeability of the conical solid iron core. This improves the performance of the position sensor in terms of sensitivity and linearity. Analytical and finite element analyses are utilized along with measurements in order to analyze the performance of the position sensor. The position sensor performs measurements of excitation coil inductance and pick-up coil voltages. Various frequencies are considered for the analysis and for the measurements. The measurement results show that the maximum linearity error is about 4% for the manufactured sensor, and is calculated to have a maximum value of 1% for the theoretical model. The achievable resolution of the proposed sensor is about 0.4 mm.

This article presents a novel configuration of the eddy current speed sensor to measure the rotating speed of iron rods and shafts up to 3000 r/min. The proposed eddy current speed sensor has an axial airgap structure with one excitation coil and two antiserially connected pick up coils. The speed sensor is mounted in the end shaft part region. Different solid iron materials for rotating shaft are considered in the measurements and calculations to evaluate solid iron material effect on the eddy current speed sensor performance. Two-dimensional (2-D) and 3-D finite element method is utilized for the performance analysis of the speed sensor. Also, a 2-D analytical method is developed for parametric analysis. A copper rod is also used to compare the speed sensor with the rotating iron shaft and copper shaft. Finally, two thin copper discs with different diameters are mounted on the solid iron shaft and their influences on the eddy current speed sensor were evaluated and measured to increase sensitivity and decrease sensor dependency on the permeability of the solid iron shaft. The achieved nonlinearity errors are about ±0.2%.

This paper presents the novel structure of an eddy current sensor for linear speed measurements. The sensor has one excitation coil and two pairs of antiserially connected pick-up coils, which are located inside and outside the excitation coil. The design and modeling of the sensor are considered with an air core and with a magnetic yoke (core) to compare their performances in terms of sensitivity and nonlinearity error. The experiments and the analysis are performed at different excitation frequencies and speeds. A novel 3D analytical method is developed and utilized for parametric analysis and for the design of this sensor. The simulation results are compared with measurements up to 16.7 m/s (60 km/h). The achieved nonlinearity error is as low as 0.3%.