Combination coating thickness gauge using a magnetic flux density sensor and an eddy current search coil

USRE35703E · kind E · reissue

Assignee

• DeFelsko Corporation · US

Inventors

• Frank Koch · Osterode, DE
• Leon C. Vandervalk · Brockville, CA
• David Beamish · Mississauga, CA

Key dates

• Filing date: Aug 28, 1996
• Grant date: Dec 30, 1997
• Expiry date: Aug 28, 2016

Classification

• Technology area (CPC —): General

Abstract

A gauge probe for a handheld combination coating thickness gauge allows the combination coating thickness gauge to measure both nonferrous coatings on ferrous substrate and nonconductive coatings on conductive nonferrous substrate. The gauge probe enables the combination coating thickness gauge to determine automatically, with a single probe, the substrate characteristics, and to effect a measurement of the coating thickness on that substrate. The technique used to measure coatings on a ferrous substrate utilizes a permanent magnet to provide a constant magnetic flux and a Hall sensor and thermistor arranged to measure the temperature-compensated magnetic flux density at one of the poles of the permanent magnet. The flux density at the magnet pole can be related to a nonferrous coating thickness on a ferrous substrate. The technique used to measure nonconductive coatings on a conductive nonferrous substrate utilizes eddy current effects. A coil near the gauge probe tip is excited by an alternating current oscillating between about 6 MHz and about 12 MHz. The coil sets up eddy currents on the surface of the conducting substrate. The resulting eddy currents set up an opposing magneti…