A sensor which conveys a displacement of an object into a change of inductance with which associated circuitry can be used for monitoring the displacement of the object. The sensor includes a coil maintained about a housing in which is disposed a ferromagnetic core about which is disposed a sleeve made of a conductive material and movable between the core and the coil with the induction of the coil variable in accordance with a predetermined relationship to the displacement of the sleeve with respect to the core with the monitoring of the change in induction indicative of displacement of the object. The sensor can be designed for determining both axial or rotational displacements of an object.
An angle-of-rotation sensor comprises a coil, a magnetically conductive element within the coil which is rotatable around an axis of rotation, the axis of rotation of the magnetically conductive element being at least partially within the coil, and a single winding for the coil. The angle-of-rotation of the magnetically conductive element is determined by measuring the change in self-inductance in the coil when the magnetically conductive element is caused to rotate.
The relative displacement of two bodies is measured by moving an electrically conducting, non-ferromagnetic wall means in proportion to the relative movement of the bodies in order to increase its overlapping, telescoping relationship to a first current conducting coil while simultaneously decreasing its overlapping, telescoping relationship to a second current conducting coil. Each of the coils are excited with an AC signal at a frequency which is at least high enough that the skin depth of the wall means is less than the physical depth of the wall means. A signal is detected which is proportional to the difference in the amplitude of the voltages across the two coils which results in improved sensitivity while improving linearity and substantially reducing temperature dependence.
A linear displacement transducer has an elongated current conducting, tubular coil which is mounted to an end cap in a hydraulic or pneumatic cylinder and extends into a hole bored in the piston/piston rod unit within the cylinder. An electrically conducting, nonferromagnetic tube lines the wall of the bore and reciprocates axially with the piston/piston rod unit varying its overlap of the coil and thereby varying the inductance of the coil at an applied frequency. An AC electrical energy source is connected to apply an AC signal to the coil, the frequency of this signal being at least high enough that the skin depth in the tubular wall is less than the physical depth of the tubular wall. A detector circuit means is connected to the coil for detecting a signal which is proportional to the coil inductance and therefore is proportional to the displacement of the piston/piston rod unit within the cylinder.
A displacement measuring apparatus including a variable inductance coil formed of a pair of coils, on a core of predetermined length made of a material having high magnetic permeability. The pair of coils are disposed on a core adjacent to each other in their axial directions and are covered by a metal sleeve of substantially the same length of one of the coils. A detecting circuit is provided including a high frequency oscillator and a rectifier and is connected to the variable inductance coil, wherein when the metal sleeve is slidably moved, the detecting circuit generates a direct current voltage in correspondence with the displacement of the metal sleeve.
A travel sensor for measuring mechanical quantities of motion, in particular for determining the brake pedal position, comprising a transmission unit axially slidable in a housing and comprising a measuring apparatus for generating an electric signal representative of the travel of the transmission unit. The transmission unit is formed of two mechanical transmissions elements (12, 13 and 3, 6, respectively) corresponding with each other and effecting a reduction of the introduced quantity of motions that the test signal is tapped by a reduced test travel. This provides a travel sensor of particularly short dimensions which permits to use of Hall-effect sensors.
