C1D2 Industrial Wireless Ultrasound Vibration Sensor, Measuring range: 20 to 100 dBµVRMS (Resolution 0.5 dBµVRMS), 2 Mile Signal Range, IP65 + Hazardous Locations Certified (UL 121201 9th Edition, Cl. 1, Div. 2), Uses 6 x AA Batteries (Not Included).