The WH31SM soil moisture sensor measures moisture content in the soil in and around your home with a 915 MHz wireless range of 300 feet (100 meters) line of sight (100 feet under most conditions). The IP66 waterproof sensor features a ceramic cap which acts like a breathing filter for exchanging soil moisture to the internal sensor. This filter makes the sensor less sensitive to soil density (clay sand soil potting soil etc.). Add up to 8 soil moisture sensors to your Ambient Weather WS-2000 and WS-5000 weather stations. The sensor supports up to 8 channels and transmits this information once per 71 seconds to the display console of your choice or our cloud service AmbientWeather.net. The information can then be accessed through the console online dashboard Amazon Alexa Google Home IFTTT and much more. You can send email text or IFTTT alerts when watering is required. The console software also allows for 2-point soil type calibration to assure accuracy. Important Note: The sensor needs to be calibrated before installing in the ground at no more than 4 inches (10 cm).