Blake-Larsen Sun Recorder
At Millbank PWS we are using the Blake-Larsen Sun Recorder which has been developed as a sophisticated recorder by Alan Blake (UK) and Ole Jul Larsen (Denmark). The recorder unit and PC software produce a fully automated system to measure the duration of bright sunlight from dawn to dusk. The system can produce results which are far more accurate than, for example, the Campbell Stokes recorder which requires manual intervention and skilled interpretation.
A note from Millbank PWS owner. We highly recommend the Blake-Larsen Sun Recorder and in addition to being affordable and very easy to install, Both Alan Blake and Ole Jul Larsen were very helpful in providing advice and help with regards to positioning the recorder and setting  up the software.