Inductive proximity switch
First Claim
1. An inductive proximity switch comprising:
- oscillator means for producing an oscillator output signal having a substantially constant frequency and a substantially constant amplitude;
sensor resonant circuit means adapted to be influenced by the approach of electrically conductive nonmagnetic nonferrous (NF) objects and ferromagnetic (FE) objects, and having a natural resonant frequency when it is uninfluenced by the approach of an object; and
coupling means for loosely coupling the oscillator output signal to the sensor resonant circuit means such that there is substantially no interaction between the oscillator means and the sensor resonant circuit means;
wherein the frequency of the oscillator output signal and the natural resonant frequency of the sensor resonant circuit means are set to deviate from each other by a predetermined frequency deviation.
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Accused Products
Abstract
An inductive proximity switch in which a quartz oscillator is connected to a sensor resonant circuit having a sensor coil which is adapted to be influenced by the approach of electrically conductive nonmagnetic nonferrous metal (NF) objects and ferromagnetic metal (FE) objects. A detecting circuit detects when the sensor resonant circuit has an impedance which is indicative of either an NF object or an FE object at a predetermined switching distance from the sensor coil, thus causing the proximity switch to exhibit the same switching distance for both NF and FE objects. The oscillator frequency and the impedance of the sensor resonant circuit at the oscillator frequency are respectively set to be equal to a critical frequency and a critical impedance value at a critical response point defined by a point where impedance-frequency characteristic curves of the sensor resonant circuit under the influence of NF objects and FE objects at the predetermined switching distance intersect. The oscillator frequency and the natural resonant frequency of the sensor resonant circuit when it is uninfluenced by an approaching object are set to be slightly different from each other.
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Citations
25 Claims
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1. An inductive proximity switch comprising:
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oscillator means for producing an oscillator output signal having a substantially constant frequency and a substantially constant amplitude; sensor resonant circuit means adapted to be influenced by the approach of electrically conductive nonmagnetic nonferrous (NF) objects and ferromagnetic (FE) objects, and having a natural resonant frequency when it is uninfluenced by the approach of an object; and coupling means for loosely coupling the oscillator output signal to the sensor resonant circuit means such that there is substantially no interaction between the oscillator means and the sensor resonant circuit means; wherein the frequency of the oscillator output signal and the natural resonant frequency of the sensor resonant circuit means are set to deviate from each other by a predetermined frequency deviation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification