Applies to electrical measuring instruments incorporating a radioactive sealed or non-dispersible unsealed source for self-calibration or for measurement, but excepting instruments used for the control of nuclear reactors for the medical diagnostic or therapeutic purposes. Recommendations concerning false indications and ease of decontaminations apply specifically to health physics instruments irrespective of whether the instruments incorporate a radioactive source. Do not apply to instruments in which the generation of ionizing radiation by the acceleration of electrons is essential to the measurement function of the instrument, e.g. X-ray sets, and radioactive sources used for measurement but not incorporated in the instruments. Concern only personal*protection against ionizing radiation, excepting precautions against the hazards of luminising compounds. Object of the standard is to specify intrinsic constructional requirements and to specify tests for showing compliance with these requirements.