I just bought those cheap type from ebay. They are a 3 in 1 meter: light, moisture and PH. I also picked up some litmus paper strips. If I see anything irregular I have a quick check. But the nutes I use are 100% organic and cannot burn the plants at all. Bat guano, worm castings, seaweed and tomato concentrate, seaweed soil conditioner and a rich mix of soil with perlite.

I don't really have to worry about burning at all, I don't even have to flush before harvest.

You can check out my grow journal in the link. I documented it every week and I mentioned everything I used on the plants.

Maybe you might never need a meter again LED Logger