Someone brought one of those UV meters out to the field a month or two
ago, probably the same one you have. As best as I recall, it was
reading 12 (extreme) outside. When put under a newish DG800, older
DG200, and very old Kestrel, it read 0. Put under a 20 y.o. LS-6 it
read 3 or 4, indicating only around 75% was being absorbed (still
better than nothing).