The ISO TS 19397 standard specifies a method for measuring coating film thickness using an ultrasonic instrument. The method is based on ultrasonic technology, which calculates the thickness of coatings by measuring the propagation time of ultrasonic waves between coatings and substrates. The standard describes in detail the operation procedures, equipment requirements, Measurement principles and error control of ultrasonic instruments, which are suitable for different types of coatings, including metals, Non-metallic and composites. This non-destructive measurement technology allows users to obtain coating film thickness data efficiently and accurately, providing a reliable basis for Coating production, quality control and engineering applications.