I’m pretty happy with my UVN800, even if it might be reading a tad high. First two attachments show OS UV (integer values) and Davis solar for 28 June 2018, a cloudless day, as recorded on WU by me and a neighbour about half-a-mile away respectively (his solar sensor is in shadow until 0845).
Next two show “cloud enhancement” on a day with “fair-weather” cloud. Expected max values here are UV=8 and solar=850 W/m
