Calibratable duct humidity / temperature sensor HYGRASGARD® KFF / KFTF (± 2.0 %) or KFF - 20 / KFTF - 20 (± 1.8 %), with plastic sinter filter (optional metal sinter filter), terminal box enclosure made of impact-resistant plastic, enclosure cover with quick-locking screws, with / without optional display. It measures the relative humidity and / or the temperature of the air and converts the measurand into a standard signal of 0 - 10 V or 4...20 mA. It has four switchable temperature ranges and is applied in non-aggressive dust-free atmospheres in refrigeration, air conditioning, ventilation and clean room technology. Relative humidity (in % r. H.) is the quotient of water vapour partial pressure divided by the saturation vapour pressure at the respective gas temperature. These measuring transducers are designed for exact detection of humidity. A digital long-term stable sensor is used as measuring element for humidity measurement. Fine adjustment by the user is possible.