Electrical metrological characterization of ironless inductive position sensors with long cables

Abstract

The ironless inductive position sensor (I2PS) is an air-cored, high-precision linear position sensor, which is designed to be immune from external magnetic fields and to work in radioactive environments. It can thus be used as a valid alternative to the linear variable differential transformer (LVDT), which unfortunately exhibits a position error in magnetic environments. These two sensors are used to determine the position of the European Organization for Nuclear Research Large Hadron Collider collimator's jaws with respect to the particle beam. Because of radiation presence in CERN accelerators, the I2PS has been designed to have no on-board electronics, the raw signal has to be carried through long cable lengths, and this may lead to performance degradation. This paper focuses on the electrical metrological characterization of the I2PS with long cables. A set of experimental measurements are conducted to assess the I2PS' sensitivity to cable capacitance change. To gain a better understanding, a comparison with a commercial off-the-shelf LVDT is presented where required. This paper also presents a novel spice simulation that models the I2PS sensor and its electronics. Furthermore, a novel countermeasure circuit is presented to rectify the effects of capacitance change.