SENSORS

HUMIDITYWhat is a humidity sensor?A humidity sensor detects the relative humidity of theambient air. This is defined as the ratio of the partialpressure of water vapor of the air, divided by the partialpressure it would have when saturated with water vaporat the temperature and pressure, usually expressed as apercentage.Common humidity sensors function by employing specialmaterials that change electrical properties such ascapacitance as they absorb moisture from, and come toequilibrium with, the surrounding air.ApplicationCasesHumidity SensingReal Life ExamplesHVACs (air conditioning units)Automotive climate controlsAppliancesImportant selection parametersHumidity RangeHumidity range is the span of relative humidity, in percent,that the device can reliably measure.SensitivitySensitivity defines the rate of change or transfer ratio ofthe output of the sensor, for a given change of humidity.Depending on the type of sensor and its output property,this can be expressed in several ways, such as pF/%RH,Hz/%RF, or mV/%RH.Typical applicationsHumidity sensors are commonly used in environmentalcontrols and monitoring devices such as home airconditioners and humidifiers, commercial HVAC systems,automotive and other vehicle cabin controls, as well asindustrial process control systems.HUMIDITY23www.FutureElectronics.com/Sensors