Over the last years, some new sensors have been developed, for monitoring photovoltaic plants. This has been possible due to close co-operation, in research and development, between Ingenieurbüro Mencke & Tegtmeyer GmbH (M&T) and Institut für Solarenergieforschung Hameln/ Emmerthal (ISFH). The new PVIS reference irradiance sensor will be available later this year, once the final optimization and accelerated environmental testing is completed. Whilst we now concentrate on this sensor, which conforms to the IEC 61724-1:2017 standard as well as with WPVS (World Photovoltaic Scale), we will present the new BigRef sensor in the next issue of PES Solar. We would like to thank all colleagues, who have made this technique possible.