Phase difference detection device for an inductive position detector

A phase difference detection device for an inductive position detector, said position detector being excited by a predetermined reference signal to generate first and second A.C. output signals, said first A.C. output signal having been amplitude-modulated using, as an amplitude coefficient, a first function value corresponding to a position-to-be-detected, and said second A.C. output signal having been amplitude-modulated using, as an amplitude coefficient, a second function value corresponding to the position-to-be-detected, said phase difference detection device comprising:

• a phase shift circuit operatively coupled to said position detector to shift an electric phase of said first A.C. output signal by a predetermined angle;
• an addition circuit operatively coupled to said phase shift circuit and to said position detector to perform an addition operation between an output signal of said phase shift circuit and said second A.C. output signal so as to synthesize a first data signal having an electric phase angle shifted in one of positive and negative directions in correspondence to the position-to-be-detected;
• a subtraction circuit operatively coupled to said phase shift circuit and to said position detector to perform a subtraction operation between the output signal of said phase shift circuit and said received second A.C. output signal so as to synthesize a second data signal having an electric phase angle shifted in other of the positive and negative directions in correspondence to the position-to-be-detected;
• a first operation circuit operatively coupled to said addition circuit to measure an electric phase difference between said predetermined reference signal and said first data signal to obtain first phase data;
• a second operation circuit operatively coupled to said subtraction circuit to measure an electric phase difference between said predetermined reference signal and said second data signal to obtain second phase data;
• and
• a third operation circuit operatively coupled to said first and second operation circuits to calculate position detection data corresponding to the position-to-be-detected on the basis of said first and second phase data.