The output of a UV lamp is measured in W/cm. It describes the electrical input, i.e. the electrical power input per centimetre of lamp length. The output of a UV LED, however, is given in W/cm². This represents the optical output, i.e. the light output per square centimetre.
The measurements carried out using LED UV systems are not currently standardised and thus cannot be compared for users. There are currently no standard measurement devices available that are calibrated according to specific standards. At the moment, the measurement devices used are calibrated for mercury vapour lamps and have an insufficient spectral sensitivity.
For comparable measurement results, the place at which the output was measured is also important. Depending on whether the measurement takes place on the chip surface, at the exit window of the radiation or on the substrate level, there will be different values. The spatial and temporal distribution in the measuring field also needs to be taken into consideration.