Method and apparatus for measuring a thickness of a nonconductive coating and calibrating a thickness measurement gauge

A method of calibrating a thickness measurement gauge including an eddy current sensor to measure a thickness of a nonconductive coating over a first surface and a second surface intersecting at an intersection angle, the first and second surfaces having a first conductivity and a second conductivity, respectively, the method comprising:

• placing the eddy current sensor at a predetermined angular orientation with respect to third and fourth surfaces intersecting at the intersection angle, wherein the third surface has a third conductivity corresponding to the first conductivity, and the fourth surface has a fourth conductivity corresponding to the second conductivity;
• positioning the eddy current sensor at a predetermined distance with respect to the third and fourth surfaces;
• and
• calibrating the thickness measurement gauge to a calibration output based on the third and fourth conductivities.

A method of measuring a thickness of a nonconductive coating over portions of a first surface and a second surface intersecting at an intersection angle with a thickness measurement gauge including an eddy current sensor, the first surface and second surface having a first conductivity and a second conductivity, respectively, the method comprising:

• placing the eddy current sensor at a predetermined angular orientation with respect to third and fourth surfaces intersecting at the intersection angle, wherein the third surface has a third conductivity corresponding to the first conductivity, and the fourth surface has a fourth conductivity corresponding to the second conductivity;
• positioning the eddy current sensor at a predetermined distance with respect to the third and fourth surfaces;
• calibrating the thickness measurement gauge to a calibration output based on third and fourth conductivities;
• placing the eddy current sensor in contact with at least a portion of the coating at the predetermined angular orientation between first and second surfaces;
• determining a measurement output of the thickness measurement gauge based on first and second conductivities;
• and
• comparing the measurement output of the thickness measurement gauge to the calibration output to determine a thickness of the nonconductive coating.

A thickness measurement gauge, comprising:

• a sensor housing;
• an eddy current sensor disposed in the housing;
• a pressure enclosure hermetically sealed to permit a pressure within the enclosure to exceed an ambient pressure;
• and
• an electronic analyzer disposed in the pressure enclosure and electrically interconnected to the eddy current sensor and adapted to analyze an electrical signal from the sensor.

A calibration stand for calibrating a thickness measurement gauge including an eddy current sensor for measuring a thickness of a non-conductive coating over portions of a first surface and a second surface intersecting at an intersection angle, the first and second surfaces having a first conductivity and a second conductivity, respectively, the calibration stand comprising:

• an eddy current sensor holder for holding the sensor;
• a calibration block having third and fourth surfaces intersecting at the intersection angle, wherein the third surface and fourth surfaces lie opposed to the eddy current sensor holder at a predetermined angular orientation, and wherein the third surface has a third conductivity corresponding to the first conductivity, and the fourth surface has a fourth conductivity corresponding to the second conductivity;
• and
• a positioner to linearly translate the eddy current sensor holder toward and away from the calibration block.

A calibration stand for calibrating a thickness measurement gauge including an eddy current sensor for measuring a thickness of a non-conductive coating over portions of a first surface and a second surface intersecting at an intersection angle, the first and second surfaces having a first conductivity and a second conductivity, respectively, the calibration stand comprising:

• an eddy current sensor holder for holding the sensor;
• a calibration block having third and fourth surfaces intersecting at the intersection angle, wherein the third surface and fourth surfaces lie opposed to the eddy current sensor holder at a predetermined angular orientation, and wherein the third surface has a third conductivity corresponding to the first conductivity, and the fourth surface has a fourth conductivity corresponding to the second conductivity;
• and
• a positioner to linearly translate the calibration block toward and away from the eddy current sensor holder.