The MT91 a Mini Bluetooth Hygrometer measures relative humidity, temperature, and dew point while the modern ergonomic design with large backlit dual display makes it easy to use in any application. Relative humidity is normally expressed as a percentage, a higher percentage means the air-water is more humid. At 100% humidity, the air is saturated and at dew point. The Bluetooth connectivity allows users to transfer and share measured data to a smart phone and the app is available on both Android and IOS platforms. Other features include Min/Max record more and data hold. Features : Dual Digital LCD Measure ambient Temperature and Humidity Data hold function Min/Max reading Bluetooth BLE Auto power off