Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1998-11-30
2001-02-20
Strecker, Gerard (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S234000, C324S236000, C324S327000, C331S065000, C307S116000
Reexamination Certificate
active
06191580
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an inductive proximity detector that can be configured to selectively detect ferrous or non-ferrous metal objects.
2. Description of the Related Art
There are many inductive detectors comprising:
a coil forming part of an LC oscillating circuit that generates an oscillation and the inductance of which is sensitive to the presence of a metal object, such that the natural frequency of the oscillating circuit varies as this type of object is brought close,
an oscillator generating a fixed oscillation independent of whether or not the object is present, that forces the oscillating circuit through coupling means, and,
a processing circuit with two inputs, firstly the fixed oscillation signal output from the oscillator, and secondly the variable oscillation signal output from the oscillating circuit and which outputs a detection signal in the presence of the object.
This type of detector, capable of selectively detecting ferrous and non-ferrous metal objects, is described in patent FR-2 716 979.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a simple detector capable of detecting ferrous and non-ferrous objects.
It is another object of the present invention to provide a detector that can be configured on the manufacturing site, or even on the usage site, depending on the nature of the metals to be detected.
In other words, the purpose of the invention is to be able to easily configure inductive proximity detectors to assign them to ferrous or non-ferrous metal detection.
According to the invention, in an inductive proximity detector of the type described above, the frequency f of the oscillation generated by the oscillator is less than the critical frequency fc of the oscillating circuit; the processing circuit comprises a phase detector provided with a first input and a second input, the fixed oscillation signal being applied to the first input and the variable oscillation signal being applied to the second output, or vice versa by means of a configuration inverter device.
The proximity detector can thus be configured in ferrous or non-ferrous mode by an inverter device with mechanical or electronic control; the simplicity of this configuration is due firstly to the fact that the invariable frequency output by the oscillator is very much lower than the critical frequency of the oscillating circuit, and that the direction of the variation of the inductance is therefore significantly different depending on whether the object is ferrous or non-ferrous; and secondly due to the fact that it is very easy to changeover signals at the phase detector input.
The configuration inverter device also makes it easy to configure the detector output, into a normally open or a normally closed output.
REFERENCES:
patent: 5519317 (1996-05-01), Guichard et al.
patent: 5767672 (1998-06-01), Guichard et al.
patent: 0 678 759 (1995-10-01), None
patent: 2 716 979 (1995-09-01), None
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Schneider Electric SA
Strecker Gerard
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