Inductive or capacitive detector
AssigneeSchneider Electric Industries SAS
InventorsChristian Charneau, Christophe Guichard
Life of this patent
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Abstract
A proximity detector including a reference oscillator and a measurement oscillator, the frequency of which depends on the proximity of an object, particularly a metal object. A detection counter value A, which is controlled by the frequency F of the measurement oscillator, is compared to a set point counter value B to create the output signal. The set point counter value B0, which is determined during the calibration operation, is corrected by a quantity C that depends mainly on the difference of the measured temperature θ compared to the calibration temperature θ0. The proximity detector may find particular application to the detection of ferrous or nonferrous objects by universal or selective, inductive or capacitive detecting elements.
Claims8
A proximity detector comprising:
- a measurement oscillator configured to transmit a pulsed signal having a frequency that is a function of a proximity of an object to be detected;
- a reference oscillator configured to transmit a pulsed signal having a frequency that does not depend on the object to be detected;
- a digital processing circuit that transmits an output signal that is a function of the signal transmitted by the measurement oscillator and a set point counter value, said digital processing circuit including a counter, wherein:
- the counter calculates a detection counter value that is a function of a number of pulses received from one of the measurement oscillator and the reference oscillator measured in a counting timing window, the counting timing window being dependent on the frequency of the other oscillator,
- the detection counter value is compared with the set point counter value by the digital processing circuit to create the output signal,
- the set point counter value is stored in a memory associated with the digital processing circuit, and is correctable depending on a temperature, and
- a calibration counter value is introduced into the memory when the detector is calibrated using an object located within a nominal range, the set point counter value being obtained by correcting the calibration counter value as a function of the temperature.
Dependencies are inferred from the claim text.