[werk_ag]

Some considerations about possible materials to cover the sensor.

The UV sensor used on the Uncle Bob unit (shown in this post), is covered with a small piece of polystyrene (from a CD cover).

"The polystyrene plate is virtually opaque to light of wavelengths 200 nm to 275 nm, with the background absorbance dropping quickly with wavelengths above 275 nm to a value of 0.400 at 300 nm and less than 0.050 by 375 nm. Polypropylene, while equally opaque at 200 nm shows slightly less absorbance than polystyrene in the lower UV wavelengths. Polypropylene decreases rapidly from approximately 3.000 at 230 nm to less than 1.000 at 240nm, with a slight secondary peak from 250nm to 290 nm"

Considering the spectral response of the UVM-30A, a polystyrene cover seems suitable. Response bellow 275nm is almost zero.

I'm now starting to investigate Liquid Optical Clear Adhesives (LOCA).
Some are completely UV transparent.