Patent ID: 6417771
Filing Date: 2002-07-09
Classification: G01V,G08B

Abstract:
A method for remote detection of objects, each object being provided with a sensor comprising at least two magnetic elements arranged in a predetermined mutual relationship representing an identity of the sensor, wherein electromagnetic signals are generated for exciting the sensor elements to produce electromagnetic reply signals, an amplitude of the electromagnetic reply signal from each sensor element being modulated by a first magnetic field (Hmod) having a magnitude-variant (AC) and a magnitude-invariant (DC) component, comprising the steps ofgenerating a second magnetic field (Hbias) with rotating field vector; detecting a frequency shift in a component of said reply signal occurring when a magnitude-invariant component of said second magnetic field balances the magnitude-invariant component of said first magnetic field (Hmod), wherein the respective sensor element is momentarily exposed to a resulting magnetic field with essentially no magnitude-invariant component; and determining an orientation of the respective sensor element from the orientation of the magnitude-invariant component of said second magnetic field, when said frequency shift occurs.