Absolute property measurements using electromagnetic sensors
First Claim
1. A method for accounting for conductor thicknesses in a sensor having at least one conductor acting as a drive to create a field for interrogating a test material and terminals for conductor connection to electrical instrumentation, said method comprising:
- forming a layered model of a sensor conductor geometry and the test material proximate to the sensor, the model including mathematical expressions that describe the physical behavior of the sensor and interactions with the test material;
dividing cross-sectional thickness of the drive geometry into multiple layers;
assigning source values across each layer of the drive; and
relating the source values to terminal values that can be measured with the instrumentation.
1 Assignment
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Accused Products
Abstract
Methods and apparatus are described for absolute electrical property measurement of materials. This is accomplished with magnetic and electric field based sensors and sensor array geometries that can be modeled accurately and with impedance instrumentation that permits accurate measurements of the in-phase and quadrature phase signal components. A dithering calibration method is also described which allows the measurement to account for background material noise variations. Methods are also described for accounting for noise factors in sensor design and selection of the optimal operating conditions which can minimize the error bounds for material property estimates. Example application of these methods to automated engine disk slot inspection and assessment of the mechanical condition of dielectric materials are presented.
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Citations
41 Claims
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1. A method for accounting for conductor thicknesses in a sensor having at least one conductor acting as a drive to create a field for interrogating a test material and terminals for conductor connection to electrical instrumentation, said method comprising:
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forming a layered model of a sensor conductor geometry and the test material proximate to the sensor, the model including mathematical expressions that describe the physical behavior of the sensor and interactions with the test material;
dividing cross-sectional thickness of the drive geometry into multiple layers;
assigning source values across each layer of the drive; and
relating the source values to terminal values that can be measured with the instrumentation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for measuring electrical impedance comprising:
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passing an excitation signal having a frequency, amplitude, and phase set by a signal generator controlled by a master microcontroller into a test circuit;
creating a first reference signal with a second signal generator that has the same frequency as the excitation signal;
combining said reference signal with at least one electrical signal from the test circuit using a data acquisition channel that contains a microcontroller; and
transmitting acquired measurement data to a host computer for processing and storing measured values. - View Dependent Claims (11, 12, 13)
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14. A method for calibrating a sensor comprising:
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placing a sensor proximate to a reference material; and
measuring the response of the sensor as the sensor is moved over the surface of the reference material for one or more operating conditions. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26-32. -32. (canceled)
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33. A method of using an eddy current sensor array comprising:
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(a) placing an engine disk on a turntable having a pneumatic cylinder;
(b) placing a shuttle inside an engine disk slot, the shuttle containing a flexible eddy current sensor array that conforms to the slot material surface and a balloon behind the sensor;
(c) measuring the sensor array response as the shuttle is scanned through the slot;
(d) rotating the engine disk to the next slot position after scanning the slot;
(e) using a single motor to control both the disk rotation and shuttle scanning;
(f) deflating the balloon prior to entry into the slot;
(g) repeating steps (b) through (f) for each slot;
(h) timing operation so that all of the data is recorded automatically, (i) converting the sensor array response into electrical conductivity and lift-off data; and
(j) displaying the conductivity and lift-off data. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40)
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41-93. -93. (canceled)
Specification