Siemens QFM2171 DUCT RH AND TEMP SENSOR, 5 PERCENT ACCURACY, RH: 4-20 4 TO 20 MA T: 4-20 MASiemens QFM2171 Duct RH and Temp Sensor, 5 percent accuracy, RH: 4 20 4 to 20 Ma T: 4 20 mA This Q Series Duct Relative Humidity Temperature Sensors monitor and transmit changes in humidity and temperature to the building control systems. These units are especially suited for applications where precise, stable humidity sensing is required. This sensor has a 5 percent accuracy rating, a 4 to 20 mA humidity output signal, and a 4 to 20 mA temperature