ppfd meter

I have used one by Phantom called PhotoBio. It is a quantum par sensor and it was free for me, I borrowed it from a buddy. :D I used it for a few days and make some PPFD maps of my one light. I should have done them all but they where interesting to work with and I did not want to borrow it to long. You can see it in weeks 2 and 3 of my honeymints diary. I liked it. There are other options out their, this one is cheeper then a Apogee, but its not as accurate still quantium par though. Apogee is setting the standard though and their stuff is king. Phone apps are garbage unless they are calibrated with something like a quantum par sensor. Maybe you can rent one to use from a shcool or something. Good Luck!