Device for converting the amount of a mechanical displacement into electrical signal

Claim 1

A transducer for converting the amount of mechanical displacement of a member (1) into an electrical signal, comprising: first coil means (9) driven by an a.c. signal (L1); second means (11, 12) disposed adjacent to said first coil means (9) for generating an induction current (L3) that varies as the change of a magnetic field produced by said first coil means (9), said second means comprising two coils (11, 12) opposite in winding direction to each other, said two coils (11, 12) being connected in series and spaced apart from each other by a predetermined distance; a movable member (8) moved by said member (1) for changing the spatial relations between said first coil means (9) and said second coil means (11, 12) by making said first and second coil means move relative to each other; means (23, 24, 25, 26) for converting the amplitude of said induction current (L3) into the duty ratio of a pulse (L6), said means comprising: a first comparator (25) for comparing said a.c. signal (L1) with a reference potential; a delay circuit (23) for delaying said a.c. signal (L1) by a predetermined angle in phase; a second comparator (24) for comparing an output signal (L2) from said delay circuit (23) with said induction current (L3); and an exclusive OR gate (26) for inputting the output signals from both comparators (25, 24); and means (27) for smoothing and converting said pulse (L6) into a d.c. current.