Patent ID: 8773113

Claim:
A system for measuring a cyclic motion of at least one ferromagnetic part in an environment made noisy by at least one electric source with an A.C. component, comprising: a first magnetometer ( 42 ) sensitive to a first moving part and configured to provide a first measured signal (m); a second magnetometer ( 48 ) sensitive to a second moving part and configured to provide a second measured signal (m′); a sensor of an image of the current in said electric source; a first filter ( 8 ) configured to calculate a first estimate, based on the image of the current in the electric source, of noise due to the electric source on the first measured signal; a second filter ( 8 ′) configured to calculate a second estimate, based on the image of the current in the electric source, of noise due to the electric source on the second measured signal, the second filter having a transfer function different from the first filter; a first subtractor ( 46 ) configured to subtract the first estimate from the first measured signal to provide a first useful signal; and a second subtractor ( 46 ′) configured to subtract the second estimate from the second measured signal to provide a second useful signal.