Design enhancements of an ironless inductive position sensor

Abstract

The ironless inductive position sensor (I2PS) has been designed to substitute the linear variable differential transformer (LVDT) in environments characterized by an external constant or slowly varying magnetic field. These two sensors are being used at the European Organization for Nuclear Research Large Hadron Collider's collimators to measure the position of the jaws with respect to the particle beam. In such environments, the LVDT suffers from drifts; hence, the I2PS has been designed to address this issue and replace the LVDT. The aim of this paper is to simplify the I2PS's moving coil design and achieve a better linearity response in the sensor's characteristic curve. Furthermore, although the I2PS performs well with a thermal compensation algorithm, it still suffers some drifts. Therefore, the aim of this paper is also to investigate if the moving coil design can be modified to obtain a sensor that has a low thermal sensitivity. This paper presents the simulation and experimental results of two moving core design changes. The first is a modification from a coil to a solid core. Apart from the obvious benefits of higher structural integrity, reduction in manufacturing time, and costs, this option provides a better linearity response. The second is the change to moving coils wound with brass. Since the brass has a lower thermal coefficient, it exhibits a smaller change in its resistance due to temperature.