Oscillating cavity paint meter

A method for measuring paint coating thickness on graphite-epoxy composites comprising the steps of:

• utilizing an operating frequency at X-band;
• and,
• utilizing a choke flange to create a non-circulating current distribution on the surface under test which responds to the top layer of unidirectional graphite.

A method for determining the thickness of a coating on metal and graphite-epoxy composites without destroying the film, the dry film layer comprising the steps of:

• utilizing a measurement cavity that oscillates at a fixed microwave frequency on the apparent length of the cavity;
• and,
• converting the frequency changes due to the apparent length of the cavity into a thickness measurement.

An electrical instrument for measuring dry paint and coating thickness on conductive and poorly conductive substrates non-destructively comprising:

• a five-walled measurement cavity that oscillates at a frequency dependent on the apparent length of the cavity when the sixth wall comprising the surface under test formed by the conductive substrates is brought into position;
• and,
• a reference cavity connected to said five-walled measurement cavity for converting frequency changes to dc level changes.

An electrical instrument for measuring dry paint and coating thickness on conductive and poorly conductive substrates non-destructively comprising:

• a five-walled measurement cavity that oscillates at a frequency dependent on the apparent length of the cavity when the sixth wall comprising the surface under test formed by the conductive substrate is brought into position;
• and,
• a microwave counter for reading cavity oscillator frequency directly.

In combination in a system for measuring the thickness of a dry film applied to a graphite/epoxy composite having graphite fibers:

• a multiwalled cavity coupled to a choke flange;
• and,
• 90-degree orientation of said coke flange with respect to the top layer of the underlying graphite fibers.