Siemens QFM4171 DUCT RH AND TEMP SENSOR, 2 PERCENT CERTIFIED, RH: 4-20 MA T: 4-20 MASiemens QFM4171 Duct RH and Temp Sensor, 2 percent certified, RH: 4 20 mA T: 4 20 mA This Q Series Duct Relative Humidity Temperature Sensor monitors and transmits changes in humidity and temperature to the building control system. This unit is especially suited for applications where precise, stable humidity sensing is required. It has a 2 percent certified accuracy rating, a 4 to 20 mA humidity output signal, and a 4 to 20 mA temperature signal.