This standard provides a technical specification for the measurement of material thickness using the ultrasonic pulse echo method, applicable to a Temperature range not exceeding 93 ° C (200 ° F). This method is suitable for thickness measurement of various materials, without touching the back surface, and can be used to evaluate the basic shape of the material and the thickness of precision machined parts, as well as to detect changes in wall thickness due to corrosion or erosion. This standard guides the user to select the appropriate Ultrasonic Thickness Gauge in various applications and to ensure the accuracy of the measurement results.