Systems and methods for detection of dielectric change in material and structure
AssigneeSouthwest Research Institute
InventorsRobert Martinez, Stephen Cerwin, Todd Goyen
Life of this patent
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Abstract
Methods and systems are described for efficiently detecting an object. The system includes at least one electrode for measuring a displacement current. The at least one electrode is coupled to a floating ground configuration provided by an op-amp, where the inverting node of the op-amp is coupled to electrode and the non-inverting node is coupled to a signal generator. The system may include a single capacitance sensor for detecting an object. Systems may include a plurality of capacitance sensors in an array configuration for detecting an object.
Claims36
A system comprising:
- a first electrode;
- a signal generator;
- an op-amp coupled to the signal generator, the op-amp comprising:
- an inverting node coupled to the first electrode;
- and
- a non-inverting node coupled to the signal generator;
- where the first electrode is indirectly driven by the op-amp and where the op-amp provides a floating ground.
The system of claim 7, the feedback connection comprising a resistor network configured for achieving a current-to-voltage gain of approximately 108 Ohms.
The system of claim 9, the buffer amplifier comprising a differential amplifier for subtracting an AC drive from the output of the op-amp.
A system comprising:
- a plurality of capacitance sensors configured for measuring displacement currents and detecting an object, each of the plurality of capacitance sensors comprising a sensor electrode;
- and
- a floating ground circuitry coupled to each sensor electrode.
The system of claim 12, where each sensor of the plurality of capacitance sensors measures displacement currents with a detection sensitivity of less than 1 picoamp.
The system of claim 16, where the guard electrode is further configured to shield the floating ground circuitry from stray electric fields.
The system of claim 18, the floating ground circuitry further comprising a buffer amplifier coupled to an output of the op-amp, the buffer amplifier configured for subtracting an AC drive from an output of the op-amp.
The system of claim 19, where the buffer amplifier references the output of each sensor electrode of the plurality of capacitance sensors to a true circuit ground.
A method comprising:
- determining displacement currents from each pixel of a plurality of pixels;
- determining an average displacement current from the displacement currents;
- comparing the average displacement current with any one of the displacement currents;
- and
- detecting an object using the comparison between the average displacement current and any one of the displacement currents.
The method of claim 25, where each pixel comprises an electrode and where the step of determining a displacement current comprises measuring the displacement current with the electrode.
The method of claim 25, further comprising providing the displacement currents to a multiplexer.
The method of claim 27, the step of comparing the average displacement current further comprising selecting a displacement current from the multiplexer.
The method of claim 28, the step of comparing the average displacement current further comprising subtracting the average current from the selected displacement current.
The method of claim 28, further comprising providing the result of the comparing step to adjusting circuitry configured for adjusting the amplitude and phase of the result.
A method comprising:
- providing a reference signal;
- comparing a displacement current to the reference signal;
- determining a difference between the reference signal and the displacement current;
- adjusting the phase and gain of the displacement current to nullify the difference;
- using the difference between the reference signal and the displacement signal to detect an object.
The method of claim 31, where the reference signal may be an average displacement current of a plurality of displacement currents.
The method of claim 31, where comparing a displacement further comprises comparing a displacement current from each pixel in an array of pixel.
A method comprising:
- receiving a displacement signal;
- determining the voltage of the displacement signal;
- setting a voltage of a reference signal to a range similar to the voltage of the displacement signal;
- determining a difference between the reference signal and the displacement current;
- amplifying the difference;
- and
- using the difference between the reference signal and the displacement signal to detect an object.
The method of claim 34, where the voltage of the reference signal is greater than the voltage of the displacement signal.
Dependencies are inferred from the claim text.