Humidity sensor ES861_ZW 1 Button. 2 x AAA BatteriesItem no. 35039 Z-Wave RH / ES 861 Z-Wave RH - is a wireless battery operated highly accurate humidity sensor designed for installation in low energy installation systems based on Z-Wave. The humidity sensor measures the humidity in the air and transmits the reading wirelessly to a central unit. The humidity sensor has a very low energy consumption as only important changes in temperature is transmitted. The measuring range is set centrally. The central unit is alerted in case of low battery and the user is prompted to change the battery.. Size: 70 x 70 x 25 mm (L x W x H). Colour: White.