Interference-tolerant proximity sensor system having a resonance-tracking impedance analyzer
AssigneeHoneywell International Inc.
InventorNick Anthony Demma
Life of this patent
Estimating the term…
Abstract
A system to analyze the impedance of interference-tolerant proximity sensors. A lock-in amplifier (LIA) is implemented as a resonance-tracking oscillator. The control loop of the amplifier monitors the response of sensor in relation to the output of a local oscillator to adjust the oscillator's frequency to resonance. The nature of the sensor acts as a pre-filter of noise for a synchronous demodulator, which demodulates the sensor's response with the local oscillator's driving signal. The output of the system is a filtered version of this demodulated signal. This system is effective in sensing objects in the presence of electromagnetic noise that is many times stronger than the signal produced by the local oscillator.
Claims21
A proximity sensor system having a resonance-tracking impedance analyzer for eliminating effects of interfering signals, comprising:
- a voltage controlled oscillator;
- a voltage-to-current converter connected to said voltage controlled oscillator;
- a resonant circuit connected to said voltage-to-current converter;
- a first demodulator connected to said resonant circuit and to said voltage controlled oscillator;
- a second demodulator connected to said resonant circuit and to said voltage controlled oscillator;
- a first filter connected to said first demodulator;
- an integrator connected to said first filter and to said voltage controlled oscillator;
- and
- a second filter connected to said second demodulator.
An interference tolerant proximity sensor system comprising:
- a voltage controlled oscillator having an input, and first and second outputs;
- a voltage-to-current converter having an input connected to the first output of said voltage controlled oscillator, and having an output;
- a resonant circuit having a terminal connected to the output of said voltage-to-current converter;
- a first multiplier having a first input connected to the second output of said voltage controlled oscillator, a second input connected to the terminal of said resonant circuit, and having an output;
- a first filter having an input connected to the output of said first multiplier, and having an output;
- an integrator having an input connected to the output of said first filter and having an output connected to the input of said voltage controlled oscillator;
- a second multiplier having a first input connected to the first output of said voltage controlled oscillator, a second input connected to the terminal of said resonant circuit, and having an output;
- and
- a second filter having an input connected to the output of said second multiplier, and having an output.
A means for interference tolerant proximity sensing, comprising:
- means for providing a first waveform at a first frequency;
- means for providing a second waveform in a quadrature phase relationship with the first waveform;
- means for converting the first waveform into a current waveform;
- means for target sensing, having a resonant circuit with a resonant frequency, which has an impedance that varies relative to a distance of a target from the resonant circuit;
- feeding the current waveform into the resonant circuit, wherein the resonant circuit converts the current waveform into a voltage waveform across the impedance and at the resonant frequency;
- means for multiplying the first waveform and the voltage waveform to provide a first resultant waveform having AC and DC components;
- and
- means for filtering out the AC component from the first resultant waveform to provide a first DC signal, which is indicative of the impedance of the resonant circuit.
A method for interference tolerant proximity sensing comprising:
- generating a first waveform at a first frequency;
- operating a second waveform having a quadrature phase relationship relative to the first waveform;
- converting the first waveform into a current waveform;
- converting the current waveform into a voltage waveform that varies in magnitude in response to an impedance in a resonant device that changes relative to distance of a target from the resonant device, wherein the voltage waveform has a resonant frequency;
- multiplying the first waveform and the voltage waveform to produce a first resultant waveform having AC and DC components;
- and
- filtering out the AC component from the first resultant waveform to produce a first DC signal that indicates an amount of impedance in the resonant circuit.
Dependencies are inferred from the claim text.