Conveyor belt having magnetic linear encoder readable magnetic markers

A conveyor comprising

• a) an endless conveyor belt with a belt periphery, an outer conveying surface, an inner pulley-facing surface, magnetic markers along the entire belt periphery except for one or more blank zone(s) each of a length Lj, wherein j is the index of the blank zone, the magnetic markers being arranged in belt travel direction such that in alternating manner the north pole or the south pole of a magnetic marker points to the outer conveying surface, adjacent such north and south poles being spaced apart from each other by a pole pitch DP, producing thereby an alternating magnetic field of a default maximum intensity:
• wherein in each of said blank zone(s) the magnetic markers are absent or produce a magnetic field of lower maximum intensity than said default maximum intensity;
• b) at least 2 position sensing units arranged along the belt periphery and in spatial proximity of the magnetic markers, each one being capable, when the conveyor belt runs in travel direction, of detecting the magnetic field from magnetic markers not being in the blank zone(s) and to produce thereby when the belt runs in travel direction, 1) a sinusoidal voltage signal about the orientation of the magnetic flux density B sensed from the magnetic markers and thus corresponding to the angular position of the position sensing unit with respect to the pattern;
• and 2) a corresponding cosinusoidal voltage signal corresponding to the angular position of the position sensing unit with respect to the pattern:
• wherein among said at least 2 position sensing units there are at least 2 spaced position sensing units of which each one is spaced apart from any one of the remaining spaced position sensing units by a peripheral distance in belt travel direction which is greater than any length Lj of any blank zone;
• c) means capable of generating a blank zone entering signal when the maximum intensity of the magnetic field detected by a position sensing unit drops, or is about to drop, down to or below a threshold intensity lower than said default maximum intensity and means capable of generating a blank zone leaving signal for that position sensing unit when the maximum intensity of the magnetic field detected by that same position sensing unit rises, or has risen, to or above said threshold intensity;
• and
• d) a control unit that derives, when the conveyor belt runs in travel direction, belt position information from the sinusoidal and cosinuosoidal voltage signals of all position sensing units, provided that the control unit disregards the sinusoidal and cosinusoidal voltage signals from any position sensing unit as from the time point that it receives said blank zone entering signal for that position sensing unit and re-considers the sinusoidal and cosinusoidal voltage signals of that position sensing unit as from the time point that it receives said blank zone leaving signal for that position sensing unit.