Specifies the performance requirements of instruments as used in the non-invasive measurement of X-ray tube voltage up to 150 kV and the relevant compliance tests. Describes the method for calibration and gives guidance for estimating the uncertainty in measurements performed under conditions different from those during calibration. This standard is not concerned with the safety aspect of such instruments. The requirements for electrical safety applying to them are contained in IEC 61010-1. THIS CONSOLIDATED VERSION CONSISTS OF THE FIRST EDITION (2002) AND ITS AMENDMENT 1 (2008). THEREFORE, NO NEED TO ORDER AMENDMENT IN ADDITION TO THIS PUBLICATION.