This International Standard is applicable to fluorometric oxygen analyzers used for the continuous determination of dissolved oxygen partial pressure or concentration. It applies to fluorometric oxygen analyzers suitable for use in water containing liquids, ultrapure waters, fresh or potable water, sea water or other aqueous solutions, industrial or municipal waste water from water bodies (e.g. lakes, rivers, estuaries) as well as for industrial process streams and process liquids. Whilst in principle fluorometric oxygen-analyzers are applicable in gaseous phases, the expression of performance in the gas-phase will not be subject of this standard. The sensor unit of a fluorometric oxygen analyzer being in contact with the media to be measured contains a luminophore in a polymer-membrane permeable for oxygen or within other oxygen permeable materials (or substrates). This standard specifies the terminology, definitions, requirements for statements by manufacturers and tests for fluorometric oxygen analyzers. This standard is in accordance with the general principles set out in IEC 60359 and IEC 60770 series. This standard is applicable to analyzers specified for permanent installation installation in any location (indoors or outdoors) utilizing an on-line measurement technique. Safety requirements are dealt with in IEC 61010-1. Standard range of analogue d.c. current signals used in process control systems are dealt with in IEC 60381-1. Specifications for values for the testing of influence quantities can be found in IEC 60654 series. Requirements for documentation to be supplied with instruments are dealt with in IEC 61187. Requirements for general principles concerning quantities, units and symbols are dealt with in ISO 80000-1:2009. The object of IEC 62703 is: – to specify the general aspects in the terminology and definitions related to the performance of fluorometric oxygen analyzers used for the continuous determination of dissolved oxygen partial pressure or concentration in liquid media; – to unify methods used in making and verifying statements on the functional performance of such analyzers; – to specify which tests should be performed in order to determine the functional performance and how such tests should be carried out; – to provide basic documents to support the application of standards of quality assurance within ISO 9001.