The GB/T 7991.5-2014 Glass-lined layer test method, Part 5: Electromagnetically measurement Film thickness standard specifies an electromagnetic measurement method for the measurement of Film thickness of Glass-lined layers on magnetic substrates. The method is based on the principle of measurement of the change in the magnetoresistance of the covering layer to the magnetic circuit of the base metal to determine the Film thickness of the Glass-lined layer. This standard applies to the testing of Glass-lined film thickness of various magnetic substrate Glass-lined equipment, providing an effective and nondestructive measurement technique to ensure the reliability and performance of the equipment during use.