Instrument for determining a quantity associated with a force exerted on a rotor

Method of determining a quantity associated with a force exerted on a rotor,

• wherein the rotor is mounted by at least one bearing so as to allow at least limited displacement relative to a stator, the bearing including opposing bearing surfaces, held generally fixed in position relative to the rotor and stator, respectively
• wherein at least one bearing has an adjustable stiffness in a direction normal to the bearing surfaces, the method including
• determining a value of a quantity associated with a second force exerted between the rotor and the stator and opposing the force associated with the quantity to be determined, and
• correcting the determined value of the quantity associated with the second force by a bias value, obtained using a mapping having as a parameter a variable representative of the parameter for adjusting the stiffness.

Method of producing an instrument for determining a quantity associated with a force exerted on a rotor, including:

• providing an instrument which includes:
• a rotor;
• a stator;
• at least one bearing for mounting the rotor to allow at least limited displacement relative to the stator, the bearing including opposing bearing surfaces, arranged to be kept generally fixed in position relative to the rotor and stator, respectively,
• at least one bearing having an adjustable stiffness in a direction normal to the bearing surfaces;
• and
• a system for determining a value of a quantity associated with a second force exerted between the rotor and the stator and opposing the force associated with the quantity to be determined, and
• obtaining data representative of a mapping between a bias value of the quantity, tending to oppose a direction of displacement of the rotor relative to the stator, and at least a variable representative of a parameter at least partly determining the stiffness of the at least one bearing.