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1. (WO1988003640) TRANSDUCTEURS DE DEPLACEMENT
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

CLAIMS :

1. A displacement transducer comprising an
oscillator (10,50); a coil (30,32); an element (34) movable in relation to the coil to vary the inductance of the coil; a network (15,56,58,76) configured around the coil and having an input terminal (14,52,54) connected to receive the output of the oscillator, the network being arranged to pass the frequency of the output of the oscillator but to give it a phase shift dependent on the position of the element; and means (18) connected to an output terminal (16,72,74) of the network for detecting the phase shift,
characterised in that the network includes two coils or two sections of a coil (30,32), and movement of said element (34) varies their mutual inductance, the two coils or two sections of a coil (30,32) being connected in series between the input terminal
(14,52,54) and the output terminal (16,72,74) of the network .

2. A displacement transducer according to claim 1, wherein the network (15,56,58,76) constitutes an all-pass filter.

3. A displacement transducer according to claim 1 or claim 2, wherein the network (15,56,58) includes a capacitor (36) connected between a common point (35) of the two coils or two sections of a coil (30,32), and ground.

4. A displacement transducer according to claim 1 or claim 2, wherein a common point (35) of the two coils or two sections of a coil (30,32) is connected to ground, and the network (15,56,58) includes a capacitor (38,40) connected in parallel with each coil or section of a coil (30,32).

5. A displacement transducer according to claim 3 or claim 4, wherein the inductance L of each coil or section of a coil (30,32) when said element (34) is in a null position is related to the capacitance C of the or each capacitor (36,38,40) and the angular frequency W of the oscillator (10) by the formula

tf = 1
LC

6. A displacement transducer according to any one of the preceding claims, wherein the means (18) for detecting the phase shift is connected to detect the difference in phase between the output of the network (15) and the output of the oscillator (10).

7. A displacement transducer according to any one of claims 1 to 5, including two said networks (56,58) configured around respective said coils (44a, 44b) having respective said movable elements (34a, 34b), the mechanical arrangement being such as to produce respective phase shifts of opposite sense in the two networks in response to an input displacement.

8. A displacement transducer according to claim 7, wherein the means (18) for detecting the phase shift is connected to receive the outputs (72,74) of the two said networks (56,58) and detect the phase difference between them.

9. A displacement transducer according to claim 1 or claim 2, wherein the network (76) includes two sets of coils or coil sections (30a, 32a; 30b , 32b) in a differential arrangement, each set comprising two said coils or coil sections and a respective said movable element (34a, 34b), the network producing two outputs" (72,74) phase shifted in opposite senses.

10. A displacement transducer according to claim 9, wherein the means (18) for detecting the phase shift is connected to receive said two outputs (72,74) and detect the phase difference between them.

11. A displacement transducer comprising an
oscillator (10,50); a coil (30,32); an element (34) movable in relation to the coil to vary the inductance of the coil; a network (15,56,58,76) configured around the coil and having an input terminal (14,52,54) connected to receive the output of the oscillator, the network being arranged to pass the frequency of the output of the oscillator but to give it a phase shift dependent on the position of the element; and means (18) connected to an output terminal (16,72,74) of the network for detecting the phase shift,
characterised in that the network (15,56,58,76) constitutes an all-pass filter, including two coils or sections of a coil (30,32), movement of said element (34) varying the mutual inductance of the coils or coil sections .