mooncity Soil pH Tester Kits, 3-in-1 Soil Meter for Moisture, Light and pH/Acidity Meter Plant Tester,Good for Gardener or Planter Both Indoor and Outdoors (No Battery Needed) Soil Level: Measure soil moisture, pH and light by just plugging in the probe Scientifically Accurate: Easy to read moisture, pH and light levels, promotes healthy plants NO Battery Required: No batteries or electricity needed, plug and read Let you know your soil: when to water, control pH level, determine if plant getting adequate light Ideal Tool: Compact and portable design for indoor/outdoor use. If the Soil Meter's Pointer does not rotate, maybe the plants are very dry! It means that your plants need to water right now!