Steel Health Monitoring Device Based on Hall Sensors

Abstract A new, portable device is presented, which can be used to monitor changes in the magnetic properties of a ferromagnetic material, such as steel, due to stresses or other effects, through measurements of magnetic flux density. The device consists of a yoke, formed of a permanent magnet, which provides a constant flux density, and two high permeability soft ferromagnetic poles. The yoke is placed above the material under test, forming a magnetic circuit. Two Hall sensors placed at the ends of the yoke’s poles measure the magnetic flux density. Through this arrangement, the ambient magnetic field is cancelled and the changes in the magnetic flux density values depend only on the changes in the magnetic properties of the sample’s material participating in the magnetic circuit. The optimal parameters of the device, such as the lift-off distance between the yoke and the sample, were selected based on simulation results. The device includes the above-mentioned sensing element, a microcontroller, a temperature sensor, an Analog-to-Digital converter, an RF transmitter, a Bluetooth module and a battery. The collected data are wirelessly transmitted to a receiving device, consisting of a microcontroller, an RF receiver, an LCD and a battery. The output information can be viewed either on the dedicated device or on any other Bluetooth-compatible device (e.g. smartphone, tablet, laptop etc).