Magnetic flux sensor for control of thick steel plates

Abstract

This paper presents a novel rugged magnetic flux sensor that can measure the thickness of steel plates and can operate reliably in the poor environment of a warehouse for thick steel plates. The sensor, consisting of a sensing plate and a sensing coil, is embedded inside the core of a lifting magnet and can be installed easily on an existing lifting magnet with minor modifications to the core. Depending on the thickness of steel plates attached to the lifting magnet, the magnetic permeability of the core and the sensing plate changes. The thickness of steel plates is indirectly measured by measuring the changes in the magnetic permeability with the sensing coil. Compared to other sensors for steel-plate control, the proposed sensor shows little hysteresis and drift problems and better dynamic responses. With a proper procedure for securing measurement reliability, it is demonstrated that the sensor can measure steel plates up to a total thickness of 30 mm with resolution better than 1 mm. (C) 1998 Elsevier Science S.A.