Sure Test GroGuru Stem with 3 Sensors is no longer available

Sure Test GroGuru Stem with 3 Sensors Questions & Answers

They don't measure pH?
No pH would be a separate sensor technology.

How large of an area does the STEM measure? Will it cover a 4'X8' grow bed or a 300 gallon Smart Pot or is it strictly for small areas?
It measures roughly a cylinder aligned along the tine end of the sensor about 2” in diameter by 3.5” in length. Therefore, you want to place the sensor or sensors in a place representative of the whole bed or you can place multiple sensors to achieve your goal.

So these tell you when to fertilize and water?
Think of them as conductivity meters or moisture meters. They are reference tools that give you values for the different parameters that they measure. This data can then help you make better decisions and when to water and if your fertilizer concentrations need to be higher or lower. You may also find this video useful https://www.youtube.com/watch?v=WAVttXRXt48