Duct Sensor for Humidity & Temperature

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The QFM3171 is for use in ventilation and air conditioning plants where high accuracy and short response times for measuring relative humidity are required. The measuring range covers the entire humidity range of 0…100 %.
The sensor acquires the relative humidity in the air duct via its capacitive humidity sensing element whose capacitance varies as a function of the relative humidity of the ambient air. An electronic circuit converts the sensor’s signal to a continuous DC 0...10 V or 4…20 mA signal, corresponding to a relative humidity of 0...100 %. The sensor acquires the temperature in the air duct via its sensing element whose electrical resistance changes as a function of the temperature. This variation is converted to an active DC 0…10 V or 4…20 mA output signal, depending on the type of sensor. The output signal corresponds to a selectable temperature range of 0…50 °C, -35…+35 °C, or -40...+70 °C.