A Hall-effect based sensor for the detection of concentrations of ferromagnetic materials in water

In this paper, the authors propose a novel sensing architecture for the detection of ferromagnetic materials suspended in water. These materials have a high magnetic permeability and are thus easily attracted by magnets and belong to the broader family of heavy metals. Their presence in water can be harmful for human health and for ecosystems as well: however, currently the only way to detect their presence is by means of laboratory analysis. The solution presented in this paper is based on the usage of a Hall effect sensor exploited to measure the magnetic field generated by a permanent magnet. Dispersed ferromagnetic particles in water are attracted by the permanent magnet, causing a change in the overall magnetic field strength which is detected by the Hall effect sensor. The sensor provides a voltage output with characteristic suitable to be easily acquired by a simple microcontroller. Laboratory tests were performed with different quantities of different types of ferromagnetic materials. The results of these tests suggest the feasibility of a measurement system able to detect small quantities of ferromagnetic contaminants in, laying the ground to the development of an integrated system to be employed for real-time field measurements.