.. highlight:: swift Humidity ======== Electronic humidity sensors (hydrometer) measure humidity by measuring the capacitance or resistance of air samples. This sensor comes packaged with the `BME280 `_ integrated environmental unit, only available on MetaEnvironment boards, and is accessible through the `MBLHygrometerBME280 `_ interface. To meet specific needs, different MetaWear models may have different hydrometers, so the ``MBLHygrometer`` class is actually a generic abstraction of all hydrometers. You can up-cast to one of our derived hydrometer objects in order to access advanced features. Cast to Derived Class --------------------- There is currently nothing in the generic ``MBLHygrometer`` class, so you need to use the `MBLHygrometerBME280 `_ derived class. :: if let hygrometerBME280 = device.hygrometer as? MBLHygrometerBME280 { }