Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Patent
1995-04-06
1996-07-30
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
32420716, 32420726, 324225, 324227, 324229, 324234, G01R 3312, G01N 2772, G01B 706, G01B 714
Patent
active
055415105
ABSTRACT:
This invention uses a single eddy current coil to measure multiple parameters of conductive target simultaneously using a single fixed frequency. For example, the system consisting of the sensor coil, connecting cable, and signal conditioning electronics, can measure the thickness of a target and the distance of the target from the coil. Alternatively, it could simultaneously measure the distance of the target to the coil, i.e. lift-off, and one of the electrical properties of the target, such as the resistivity. The present system is useful in material characterization of targets where the lift-off information can be used to correct for any lift-off induced error in the apparent resistivity. In general, it can determine any pair of two characteristics of the target/sensor relationship simultaneously. This invention provides significant improvement in accuracy and flexibility of eddy current sensors and can be manufactured at a low cost due to the use of a single coil and a single fixed frequency in the signal conditioning electronics. An alternative sensor configuration utilizing two sensors differentially to produce a cladding insensitive--displacement measurement is also contemplated by the present invention.
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Kaman Instrumentation Corporation
Strecker Gerard R.
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