This standard is applicable to transmission-type instruments designed for the measurement of the density (i.e. the density of the irradiated material being measured) of liquids, slurries or fluidized solids. Safety aspects are not included in this standard but should fulfil the requirements of all relevant internationally accepted standards. Lays down definitions and test methods for the above desity meters, in detail: definitions relating to the measurement or control function, definitions relating to the apparatus, test methods for instability, mean response time, mean settling time, recovery time, linearity, supply voltage changes, humidity and temperature, moreover some special tests. Appendix A gives extracts from IEC Publication 359.