Patent ID: 6191580
Filing Date: 2001-02-20
Classification: G01V

Abstract:
An inductive proximity detector configurable to detect ferrous and non-ferrous objects, comprising:an oscillating circuit configured to generate a first signal at a frequency dependent on the proximity of a metal object to said oscillating circuit;an oscillator coupled to said oscillating circuit and configured to generate a second signal at a fixed oscillator frequency below a critical frequency of said oscillating circuit;a processing circuit configured to receive said first and second signals and to generate a detection signal;wherein said processing circuit comprises,a phase detector having a first input and a second input, said phase detector being configured to measure a phase difference between said first and second signals and to output a third signal based on said phase difference, said detection signal being based on said third signal; andan inverter device configured to provide,a first input configuration for said phase detector, wherein said first input of said phase detector receives a signal corresponding to said first signal and said second input of said phase detector receives a signal corresponding to said second signal, anda second input configuration for said phase detector, wherein said first input receives a signal corresponding to said second signal and said second input receives a signal corresponding to said first signal,whereby said processing circuit provides two phase detections, a first phase detection based on said first input configuration and a second phase detection based on said second input configuration, one of said two phase detections corresponding to a detection of ferrous objects and another one of said two phase detections corresponding to a detection of non-ferrous objects.