Development of an Autonomous Magnetic Permeability Sensor

In our days, there is an undeniable need for control over the quality of metals in machines, metal components, tools, and construction materials during production and maintenance. Nondestructive testing sensors have been proven to be the most effective way of determining the quality of the composition of materials since they can detect flaws, not only during their construction but also during maintenance, without interfering with, or obstructing, their use. This article focuses on the measurement of the magnetic permeability of ferromagnetic steels and alloys as a nondestructive method of correlating magnetic properties with residual stresses based on the use of a yoke-shaped sensor. Most importantly, an electromagnetic energy harvesting system has been designed and tested, based on the exploitation of mechanical vibrations. The combination of the sensor and the energy harvesting system can lead to an energy autonomous device, which can be placed in inaccessible locations for remote nondestructive testing where measurements can be taken and transmitted autonomously every 10 min. Said transmission is realized by a network of yoke sensors in multiplex configuration and sent to a central sensor, leading to an Internet of Things usable device.