Patent attributes
The invention relates on an oval gear meter for volume flow measurement comprising a housing with an oval gear chamber with a fluid inlet and a fluid outlet, a pair of oval gear wheels positioned in the chamber and together forming an intermeshing or non-intermeshing involute toothing, and a contactless magneto-reactive sensor means positioned outside of the chamber. At least one of the oval gear wheels is provided with at least one permanent magnet to form a trigger wheel. The sensor means is positioned in an appropriate position relative to the trigger wheel so that the sensor means is adapted to measure the rotation of the oval gear wheels by measuring the rotation of the trigger wheel. The trigger wheel is provided with a permanent magnet that generates a generally homogeneous magnetic field along one axis of symmetry of the trigger wheel so that the magnetic field is generally symmetrical relative to the rotational axis of the trigger wheel. The sensor means is designed as a GMR-spin valve sensor means and is positioned generally concentrically relative to the rotational axis of the trigger wheel.
