This meter is very simple but a must have in my opinion. I did not use it right away on my first grow and what a mistake. I over watered early on in my grow and am nursing plants back to health now because of it. I use this now always to help me to not overwater.

Doesnt work.
Like anything it can can fail and there is no way to calibrate it. Compared to test fluids and PH paper it is about 2 points more alkaline than they are. Meaning it reads more to the alkaline side. I would not buy it again. I would suggest you purchase a device that has the ability to calibrate it. Dont place the blame on the seller as there is now way to know it works or doesnt.
MDG