A magnetic sensor for measuring plastic pellet flow

The measurement of the flow of a granular material is an important task in several engineering fields. The ability to carry out such measurement in adverse conditions is also required, especially in industrial environments, when it is necessary to work on complex plants and it is important to obtain data about the process without affecting it. This may impose the development of specific sensors and the use of sophisticated signal processing techniques to obtain the required information. This article deals with the design, development, building and characterisation of a magnetic sensor useful for estimating the material flow of granular plastic pellets, based on magnetic marking of the reacting material and analysing the signal obtained by a detection coil while the pellets pass through a suitable magnetic field.