US 6,714,023 B2 · Method for high-accuracy non-contact capacitive displacement measurement of poorly connected targets

Abstract

A non-contact capacitive displacement measurement gage that provides high accuracy displacement measurements of well-connected targets and poorly-connected targets. The capacitive displacement measurement gage includes a capacitive probe, first and second amplifiers, and a signal generator. The capacitive probe includes a sensor electrode, a guard electrode, and a compensating electrode. The signal generator provides a predetermined voltage signal directly to the sensor electrode, to the guard electrode through the first amplifier having unity gain, and to the compensating electrode through the second amplifier having a predetermined transfer function. The second amplifier assures that substantially zero current is driven into the target element by the probe during gage operation, thereby allowing highly accurate displacement measurements of target elements having unknown or poorly controlled impedance.

Claims29

Dependent claims

A capacitive displacement measurement system, comprising:

at least one capacitive probe including a sensor electrode, the capacitive probe being configured to detect a capacitance between the probe and a target element, the detected capacitance corresponding to a displacement of the target element;
a first excitation signal generator configured to provide a first excitation signal to the sensor electrode, the sensor electrode producing a first drive signal in response to the first excitation signal;
and
a compensating subsystem including a second excitation signal generator and a compensating electrode,
wherein the second excitation signal generator is configured to provide a second excitation signal to the compensating electrode, the compensating electrode producing a second drive signal in response to the second excitation signal, and
wherein the second drive signal produced by the compensating electrode is operative to compensate for the first drive signal produced by the sensor electrode to assure that substantially zero current is driven into the target element.

3 more elements

A method of operating a capacitive displacement measurement system, comprising the steps of:

providing a first excitation signal to at least one capacitive probe by a first excitation signal generator, the capacitive probe including a sensor electrode;
producing a first drive signal in response to the first excitation signal by the sensor electrode;
detecting a capacitance between the capacitive probe and a target element by the capacitive probe, the detected capacitance corresponding to a displacement of the target element;
producing a second drive signal by a compensating subsystem, the compensating subsystem including a second excitation signal generator and a compensating electrode, wherein the second producing step includes providing a second excitation signal to the compensating electrode by the second excitation signal generator, and producing the second drive signal in response to the second excitation signal by the compensating electrode, and
compensating for the first drive signal produced by the sensor electrode by the second drive signal produced by the compensating electrode to assure that substantially zero current is driven into the target element.

2 more elements

Dependencies are inferred from the claim text.

Method for high-accuracy non-contact capacitive displacement measurement of poorly connected targets

Life of this patent

Method for high-accuracy non-contact capacitive displacement measurement of poorly connected targets

Life of this patent

Abstract

Claims29