JB/T 13939-2020 "eddy current thickness gauge for nondestructive testing instruments" specifies the terms and definitions, technical requirements, test equipment, test methods, inspection rules, signs, Encasement, transportation and storage of eddy current thickness gauges. This standard applies to eddy current thickness gauges for measurement of the thickness of non-metallic coatings on the surface of metal substrates, and their performance is tested after newly manufactured and neutralized maintenance. The standard refers to a number of relevant specifications, such as Encasement Storage and Transportation Illustration Marks, General Technical Requirements for Testing Machines, General Specifications for Electronic Measuring Instruments and Nondestructive Testing Term eddy current testing, to ensure that eddy current thickness gauges meet the standard requirements in all aspects and ensure measurement accuracy and Reliability.