Pulsed excited proximity sensor
AssigneeEaton Corporation
InventorTimothy A. Christensen
Life of this patent
Estimating the term…
Abstract
A proximity sensor has a transducer coil that is part of an oscillator circuit. The oscillating signal varies as a function of the presence or absence of a metallic object adjacent the transducer coil. By analyzing selected characteristics of that oscillating signal, the presence of and object and the distance to the object can be determined. Other analysis techniques enable the sensor to distinguish between ferrous and non-ferrous materials. A mechanism also is provided to automatically configure operation of the proximity to avoid interference from another adjacent proximity sensor.
Claims39
A proximity sensor for detecting presence of a metallic object, said proximity sensor comprising:
- a transducer coil;
- a drive circuit connected to the transducer coil to generate an oscillating signal having a waveform that varies in response to whether or not a metallic object is adjacent to the transducer coil;
- and
- a processing circuit connected to the drive circuit to measure a Q factor of the transducer coil in response to the characteristic of the waveform, and in response produce an indication of whether or not a metallic object is adjacent to the transducer coil.
A proximity sensor for detecting presence of a metallic object, said proximity sensor comprising:
- a transducer coil;
- a drive circuit connected to the transducer coil to generate an oscillating signal having a waveform that varies in response to whether or not a metallic object is adjacent to the transducer coil;
- a processing circuit connected to the drive circuit to detect a characteristic of the waveform selected from a group consisting of frequency and rate of signal decay, and in response produce an indication of whether or not a metallic object is adjacent to the transducer coil;
- and
- a detector connected to the transducer coil to determine whether a signal in the transducer coil is produced by another proximity sensor and if so, said detector configures operation of the drive circuit to avoid conflict between an oscillating signal resulting from the drive circuit and signals produced by another proximity sensor.
A proximity sensor for detecting presence of a metallic object, said proximity sensor comprising:
- a transducer coil and a capacitor connected in parallel to form a resonant circuit;
- a drive circuit connected to the resonant circuit to apply an electric pulse to the resonant circuit which causes the resonant to produce an oscillating signal;
- and
- a processing circuit connected to the drive circuit to measure a frequency of the oscillating signal, and having a comparator coupled to the resonant circuit and providing an indication when an oscillation of the oscillating signal exceeds a predefined voltage and in response thereto produce an indication of whether or not a metallic object is adjacent to the transducer coil.
A proximity sensor for detecting presence of a metallic object, said proximity sensor comprising:
- a transducer coil;
- a drive circuit connected to the transducer coil to generate an oscillating signal having a frequency that varies in response to whether or not a metallic object is adjacent the transducer coil;
- and
- a processing circuit connected to the drive circuit to detect a frequency of the oscillating signal and in response indicate whether or not a metallic object is adjacent the transducer coil, the processing circuit including a reference oscillator that produces a reference signal, a circuit connected to the transducer coil and the reference oscillator to produce an output signal that indicates a difference in frequency between the oscillating signal and the reference signal, and a counter connected to the circuit and providing a count of pulses of the output signal that occur during a given period of time.
A method for detecting presence of a metallic object, said method comprising:
- exciting a transducer coil to generate an oscillating signal having a waveform that varies in response to whether or not a metallic object is adjacent to the transducer coil
- measuring the frequency of the oscillating signal by counting cycles of the oscillating signal flowing through the transducer coil;
- and
- in response to the frequency of the oscillating signal producing an indication of whether or not a metallic object is adjacent to the transducer coil.
A method for detecting presence of a metallic object, said method comprising:
- applying an electrical pulse to a resonant circuit that has a transducer coil and a capacitor connected in parallel, which thereby generates a decaying oscillating signal;
- and
- analyzing the decaying oscillating signal to determine a Q factor;
- and
- in response to the analyzing, producing an indication of whether or not a metallic object is adjacent to the transducer coil.
A proximity sensor for detecting presence of a metallic object, said proximity sensor comprising:
- a transducer coil;
- a drive circuit connected to the transducer coil to generate an oscillating signal having a waveform that varies in response to whether or not a metallic object is adjacent to the transducer coil;
- a processor connected to the drive circuit to detect a characteristic of the waveform and in response produce an indication of whether or not a metallic object is adjacent to the transducer coil;
- and
- a detector connected to the transducer coil to determine whether a signal in the transducer coil was produced by another proximity sensor and if so said detector configures operation of the drive circuit to avoid conflict between an oscillating signal resulting from the drive circuit and signals produced by another proximity sensor.
Dependencies are inferred from the claim text.