This document, while providing a basis for the development of future individual recommendations concerning constructional requirements for the various classes of instruments within the scope, is kept very general, to facilitate its application to the large family of instruments considered. It can also serve as a guide for the writing of contracts between manufacturers and users. Gives safety recommendations, mechanical recommendations, electrical recommendations, recommendations concerning the measured physical or chemical quantity, recommendations concerning the radiometry as well as test conditions and methods for the chracteristics to be measured and radiometric tests.