Apparatus and Method for Ferromagnetic Object Detector

摘要

An apparatus is provided for compensating for the effect of a stray ferromagnetic object moving past but not through a sensing region of a ferromagnetic object detector. The ferromagnetic object detector is of a type to produce a plurality of sensor signals, each sensor signal being influenced by the presence of a genuine ferromagnetic object moving through the sensing region but also liable to be influenced by the presence of the stray object. The apparatus comprises: an input for receiving the plurality of sensor signals and first means for analysing the received signals to determine whether there is a substantially same time-varying component present in each of the signals. The apparatus also comprises second means for determining whether the plurality of signals without the contribution of that time-varying component are each or collectively below a predetermined level of significance. The apparatus also comprises third means for indicating, if the respective determinations from the first and second means are both positive, that the received signals are likely to relate to a stray object and not to a genuine ferromagnetic object moving through the sensing region.