Plantonix 3-in-1 soil meter is perfect for indoor or outdoor plants! Measure soil moisture, PH, and light levels, no batteries required! Duo-needle Detection Technology strongly enhances the speed and accuracy of detecting and analyzing soil moisture and pH acidity. The information is available at a quicker time than with a single needle, helping you know when you need to water your plant, or what to adjust to best support your plant's needs. To use, simply insert the meter's probes into your soil. You'll want to move the probes around just a bit, and then leave it in your soil for 10 minutes to ensure a proper reading. On the front of the meter, there is a switch to control what you are measuring. Farthest left is moisture, farthest right is PH, and the middle is light. Once you've taken your measurement, pull your probes out and wipe off any remaining soil, and then you're done! No batteries means no need to turn anything off, just store the meter in a safe place for the next time you need it!