Portable paint thickness gauge for composite materials using resonant cavities at x-band

摘要

A measuring instrument and method for measuring paint and coating thickness on conductive and poorly conductive substrates. The instrument uses a microwave amplifier, a measurement cavity, and a reference cavity with supporting electronics to measure the apparent changes in the length of the measurement cavity due to the changes in the paint and coating thickness. The measurement cavity resonates when the measurement cavity is set upon the test surface. The oscillating signal is sent through a reference cavity tuned to give the desired filtered response to cover the paint and coating thickness range allowed. The filtered response of the reference cavity is converted to a dc level signal that serves as input to a data acquisition circuit. The data acquisition circuit converts the input signal to digital form so that the calibration method may be used to associate a given response with the corresponding paint and coating thickness.