Abstract: An improved non-contact capacitive displacement sensor that may be employed for accurately measuring small distances between the sensor and shaped targets. The non-contact capacitive displacement sensor includes a probe having a sensor element and a guard element. The guard element substantially surrounds the sensor element. At least the sensor element has a shape that substantially matches the shape of a target element.

Abstract: An improved non-contact capacitive displacement sensor that may be employed for accurately measuring small distances between the sensor and shaped targets. The non-contact capacitive displacement sensor includes a probe having a sensor element and a guard element. The guard element substantially surrounds the sensor element. At least the sensor element has a shape that substantially matches the shape of a target element.

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.

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.

Abstract: A method for facilitating field replacement of sensors is presented. The replacement sensor's transfer function need only be measured, not adjusted, and the signal-processing unit's transfer function need only be adjusted, but not measured, to achieve simple field-replacement of sensors. With this method simple calculations and adjustments, typically expedited by means of a computer program, can be made in the field when sensor replacement is required. By way of the presently disclosed method sensor cost and size are not increased since no normalization techniques or components are required.

Abstract: A process for obtaining the periodic component in a data vector of data taken of a sensed property of an element driven by one or more rotary components over several rotations. The procedure comprises first forming the data vector asynchronously with respect to rotation of said one or more rotary components. A series of marker signals representing the rotation of the one or more rotary components is also established. From these the periodic component of data in said data vector is determined as a function of the data in the data vector and the marker signals.

Abstract: A mechanism to provider a bootstrapped power source for a differential operational amplifier includes a three-winding transformer having a first winding disposed between a positive voltage and a plus power input to the amplifier, yielding an initial plus voltage, a second winding disposed between a negative voltage and a minus power input to the amplifier yielding an initial minus voltage, and a third winding disposed between a ground and a plus input to the amplifier providing a feedback path. The differential operational amplifier output is connected to ground. The said amplifier minus input is connect to a signal and when the signal is displaced a first amount from a first voltage, the plus and minus power inputs are displaced approximately the same amount from the initial positive and negative voltages.

Abstract: A process for obtaining the periodic component in a data vector of data taken of a sensed property of an element driven by one or more rotary components over several rotations. The procedure comprises first forming the data vector asynchronously with respect to rotation of said one or more rotary components. A series of marker signals representing the rotation of the one or more rotary components is also established. From these the periodic component of data in said data vector is determined as a function of the data in the data vector and the marker signals.

Abstract: A capacitive displacement sensor for measuring thin targets is presented. The plate of the measurement probe is designed to take into account the thin target shape and to provide accurate measurements of the thin target by reducing lateral movement sensitivity of the plate. The probe may also include a guard to reduce capacitive coupling of the plate with other structures which would affect the accuracy of the measurement.

Abstract: A nonlinear current mirror for loop-gain control incorporates a resistor in one section of a current mirror which produces a nonlinear transfer function for the current mirror. When the nonlinear current mirror is included as part of a capacitive displacement gauge the gain of the gauge varies as a function of the input to the current mirror which compensates for the change in gain caused by the probe capacitance. Accordingly, the distance range and/or frequency response of the capacitive displacement gauge is increased.

Abstract: An apparatus for bootstrapping an amplifier of a capacitive displacement transducer. The apparatus replaces a transformer with two capacitors and two resistors configured to provide biased supply voltages to the positive and negative power supply connections of an amplifier configured as a high impedance unity gain buffer in the transducer. The replacement of the transformer with a pair of standard capacitors and resistors provides for similar performance at a reduced size and cost.

Abstract: A capacitive gaging system comprising a capacitive displacement sensor and an interface circuit is used to replace a Linear Variable Differential Transducer (LVDT). An output of the capacitive displacement sensor is modified by the interface circuit which provides an output signal or signals representative of different types of LVDT outputs. The capacitive displacement sensor and the interface circuit can then be used to replace the LVDT in an LVDT measurement system. Accordingly, the capacitive displacement sensor and the interface circuit replace the LVDT without replacing the rest of the measurement system.

Abstract: A measurement station which rotates a wafer in a vertical plane and moves a scanning sensor linearly along an axis which is parallel to the wafer rotation plane, thus providing a spiral, or other, scan path across the wafer. The vertical orientation reduces errors from weight induced sagging, especially of large, e.g. 300 mm wafers. The measurement station includes wafer grippers which move in the wafer's plane for securing the wafer in position for rotation. The measurement station also includes master calibration gauges which simplify calibration and obviate the need for calibration test wafers. A technique for reducing vibration and assuring scan repeatability includes coasting of the wafer in rotation and coordinated linear probe motions for scanning. Probe measurement data obtained is digitized early and calibration, demodulation, filtering and other processing is done digitally.

Abstract: An edge detection system for measuring lateral position in the presence of height variations such as found in gauging the edge position of a wafer uses first and second capacitive probes formed of passive elements with the active components kept outside the probe and at a distance that permits a smaller, stabler and more economical probe to be located at the location of the wafer. The probes are instrumented in an electronic circuit having plural operational amplifiers that drive the probes to compensate the edge detection for wafer height effects.