Patent ID: 7414530
Filing Date: 2008-08-19
Classification: G05B

Abstract:
1. A monitoring circuit for monitoring a position of a target, comprising: an inductive system having a plurality of air core inductors and a plurality of capacitors, the inductive system being operable to change its frequency response depending on a distance between the target and the inductive system; and an evaluation unit having a plurality of band filters, a center frequency of a first band filter corresponding to a first frequency and a center frequency of a second band filter corresponding to a second frequency, a threshold value of the first frequency corresponding to a lower frequency of the inductive system at a first target position, the second frequency corresponding to a resonating frequency of the inductive system at a second target position, the first band filter being operable to allow through a first signal having the first frequency and the second band filter being operable to allow through a second signal having the second frequency, wherein the monitoring circuit monitors an opened state and a closed stated of a door of an aircraft constituting said target.