Fluid flow measuring device and armature comprising a fluid flow measuring device

A fluid flow measuring device, comprising:

• a rotatable magnetic element positioned in a fluid flow, wherein the rotation of the rotatable magnetic element depends on the fluid flow, and wherein the rotatable magnetic element has a positive pole and a negative pole and generates a magnetic field;
• at least one sensing coil pair each having a first sensing coil and a second sensing coil;
• wherein the respective sensing coils of each of the at least one sensing coil pairs are arranged in such a way that the magnetic field generated by the fluid flow dependent rotation of the rotatable magnetic element has a first phase in the region of the respective first sensing coil and a second phase in the region of the respective second sensing coil, wherein said first phase and second phase differ from each other;
• wherein, for each of the at least one sensing coil pairs, the first sensing coil is positioned at a first circumferential position relative to the rotatable magnetic element and the second sensing coil is positioned at a second circumferential position relative to the rotatable magnetic element, wherein an angle between the first circumferential position and the second circumferential position is in the range of 180°±5°;
• and
• wherein for each of the at least one sensing coil pairs, the first sensing coil and the second sensing coil are connected in series to provide a subtraction of their signals thereby reducing noise caused by a disturbing magnetic field.

A fluid flow measuring device, comprising:

• a rotatable magnetic element positioned in a fluid channel and thus in a fluid flow, wherein the rotation of the rotatable magnetic element depends on the fluid flow, and wherein the rotatable magnetic element has a positive pole and a negative pole and generates a magnetic field;
• at least one sensing coil pair each having a first sensing coil and a second sensing coil;
• wherein the respective sensing coils of each of the at least one sensing coil pair are arranged in such a way that the magnetic field generated by the fluid flow dependent rotation of the rotatable magnetic element has a first phase in the region of the respective first sensing coil and a second phase in the region of the respective second sensing coil, wherein said first phase and second phase differ from each other;
• the respective first sensing coil of each of the at least one sensing coil pairs is positioned around a respective first ferromagnetic core that is positioned at a first circumferential position relative to the rotatable magnetic element, wherein the first ferromagnetic core guides the magnetic field generated by the rotatable magnetic element to the first sensing coil;
• the respective second sensing coil of each of the at least one sensing coil pair is positioned around a respective second ferromagnetic core that is positioned at a second circumferential position relative to the rotatable magnetic element, wherein the second ferromagnetic core guides the magnetic field generated by the rotatable magnetic element to the second sensing coil;
• wherein an angle between the corresponding first circumferential position and the corresponding second circumferential position is 180°±5° and wherein the respective first sensing coil and the respective second sensing coil are connected in series to provide a subtraction of their signals thereby reducing noise caused by a common mode magnetic field;
• and
• wherein the respective ferromagnetic cores are positioned within corresponding recesses in the housing outside of the flow channel and thereby outside the fluid flow.