This Meter checks PH(potential of Hydrogen)level of the soil(Acid or Alkaline level)for the plant life.And more it adds the proper amount of limeto the soil necessary for neutralization.It抯 self-powered and no battery needed.It抯 also easy to be used either indoors or outdoors.You can just place its probe tube in the tested soil at depth of 5cm approx.for about one minute after strongly scratching and cleaning the probe tip & tube with fine sandpaper.And then directly reading the value on the meter to identify the soil condition for plant life.