20-30$ lol… We pay more for our PH pens, but the difference in accuracy I don’t think is worth it, although if you buy one measure it against your two phones and let’s see the difference.
@EastCoastP6
32k = 500 PPFD. = 32.4 DLI
39k =600 PPFD =38.8 DLI
As you can see from above much can be gained in veg from a higher PPFD /DLI for the majority of the veg cycle.