Magnetic protection device

A fluid meter comprising a measurement chamber and an enclosure containing a totalizing counter separating by at least one wall made of non-magnetic material, and axial spinner situated in said measurement chamber being immersed in said fluid, and a shaft in coaxial alignment with said spinner and mechanically connected to said totalizing counter, a rotary drive system magnetically coupling together the axial spinner and the shaft of the counter and comprising at least two axially magnetized elements comprising two parts of magnetic material which are secured respectively to said axial spinner and to said shaft of the totalizing counter, characterized in that said fluid meter includes a protection device for protecting said drive system against an external magnetic field and includes an additional wall cooperating with at least one wall in contact with the enclosure to define an additional chamber disposed between the enclosure and the measurement chamber, wherein the two parts of magnetic material are situated in the additional chamber and are separated from each other.