Motion Induced Eddy Current Sensor for Non-Intrusive Vibration Measurement

When implementing temporary vibration monitoring of mechanical equipment, it is hoped that the installation and disassembly of the sensor will not change the original structure of the equipment. In that case, non-intrusive vibration sensors are preferable. This paper presents a motion induced eddy current sensor that can non-intrusively acquire vibration signal from the surface of metal objects. The sensor consists of a cylindrical permanent magnet and a pancake coil coaxially placed under it. The permanent magnet is used to generate a static magnetic field and the coil is used to pick up the eddy current signal induced by vibration. The results of principle experiments indicate that the output signal of the sensor has a linear relationship with the vibration acceleration/velocitywhen the measured object is a non-ferromagnetic/ferromagnetic metallic specimen. Two application measurement experiments are also done. When the sensor is placed on the metallic panel of a weighting scale, the ballistocardiogram (BCG) of the human body can be effectively obtained. Another experiment is carried out on a rotor test bed. When the sensor is placed above the bearing support with a fixed lift distance, satisfying vibration signals can be obtained compared with that from the conventional piezoelectric accelerometer. The present works show that the simple-structure, low-cost, non-intrusive vibration sensor (MIECS) can be applied in various fields.