ASTM E797-05

1.1 This practice² provides guidelines for measuring the thickness of materials using the contact pulse-echo method at temperatures not to exceed 200°F [93°C].

1.2 This practice is applicable to any material in which ultrasonic waves will propagate at a constant velocity throughout the part, and from which back reflections can be obtained and resolved.

1.3 The values stated in either inch-pound or SI units are to be regarded as standard. The values given in brackets are for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

The techniques described provide indirect measurement of thickness of sections of materials not exceeding temperatures of 200°F [93°C]. Measurements are made from one side of the object, without requiring access to the rear surface.

Ultrasonic thickness measurements are used extensively on basic shapes and products of many materials, on precision machined parts, and to determine wall thinning in process equipment caused by corrosion and erosion.

Recommendations for determining the capabilities and limitations of ultrasonic thickness gages for specific applications can be found in the cited references.^{5 ,6}