Patent ID: 7323863

Claim:
An inductive displacement sensor comprising: first and second elements arranged to be movable relative to each other along at least a first measuring axis, the first element comprising a set of at least two respective windings arranged along the first measuring axis, the second element comprising a structure having electromagnetic characteristics that are spatially periodic along the first measuring axis, wherein the respective effective inductance of each respective winding varies periodically as a function of the relative displacement of the two elements along the first measuring axis; and a measurement circuit comprising a driver and at least two respective measurement signal capturing portions; wherein: a first end of each respective winding is connected to a first circuit node; a second end of each respective winding is connected to a respective measurement signal capturing portion and the first terminal of a respective series component; the second terminal of each respective series component is connected to a second circuit node; the driver is connected to the first circuit node and adapted to generate simultaneous time-varying signals at the second end of each respective winding; the respective signal capturing portions are adapted to capture respective measurement signals arising from the simultaneous time-varying signals; and the displacement sensor is configured such that a combination of values comprising a measurement period value of the measurement circuit, a nominal inductance value of the respective windings, and a non-inductive impedance value that acts in series with the nominal inductance value, cause a second spatial harmonic error component of the inductive displacement sensor to be suppressed.