This International Standard describes procedures for evaluating the following performance characteristics of ultrasonic pulse-echo examination instruments:  horizontal limit and linearity;  vertical limit and linearity;  resolution-entry surface and far surface;  sensitivity and noise;  accuracy of calibrated gain controls. Relevant terminology can be found in ASTM Terminology E 1316 and IEEE Standard 100. Evaluation of these characteristics is intended to be used for comparing instruments or, by periodic repetition, for detecting long-term changes in the characteristics of a given instrument that may be indicative of impending failure, and which, if beyond certain limits, will require corrective maintenance. Ultrasonic examination instruments using pulsed-wave trains and A-scan presentation (rf or video) may also be evaluated. The procedures are applicable to shop- or field-conditions and additional electronic measurement instrumentation is not required. This International Standard establishes no performance limits for examination systems; if such acceptance criteria are required, these must be specified by the using parties. Where acceptance criteria are implied herein they are only for the sake of example and are subject to more or less restrictive limits imposed by customer's and end user's controlling documents. The specific parameters to be evaluated, conditions and frequency of test, and report data required, must also be determined by the user. This International Standard may be used for the evaluation of a complete examination system, including transducer, instrument, interconnections, fixtures and connected alarm and auxiliary devices, primarily in cases where such a system is used repeatedly without change or substitution. This International Standard is not intended to be used as a substitute for calibration of a system to inspect any given material. Required test apparatus includes selected reference blocks and a precision external attenuator (where specified) in addition to the instrument to be evaluated. Precautions relating to the applicability of the procedures and interpretation of the results are included. Alternate procedures, such as examples described in this International Standard, or others, may only be used with customer approval.