Rotronic CL11 Indoor Air Quality Data Logger. The Rotronic CL11 benchtop display unit is the latest development of an inexpensive multimeter which simultaneously measures and records CO 2 , humidity and temperature. It is equipped with the field-tested Rotronic Hygromer® IN-1 humidity sensor. Using the Rotronic software package SW2.x (supplied/downloadable), it can easily be set to record as required and data can then be downloaded, saved and analyzed. Power supply is by AA (x4) batteries.. Measures and logs CO 2 , relative humidity and temperature Hygromer® IN-1 humidity sensor 40,000 data point memory for CO 2 , humidity and temperature values Maximum, minimum and average value display Adjustable audible CO 2 alarm Real time clock with backup battery Includes software for configuration and data download