The focal plane is cooled to 100 mK by means of an open cycle dilution refrigerator. This type of refrigerator has been designed for satellite applications (it will be used on Planck HFI) and Archeops is the first balloon-borne experiment using a dilution refrigerator. The bolometers are placed on the 100 mK stage supported by Kevlar cords. The bolometers are biased using AC square waves by a capacitive current source. Their output is measured with a differential preamplifier (the first stage uses JFET working at about 120 K) and digitized before demodulation, with boxes already designed in preparation for Planck HFI. Data ampled at 152 Hz are compressed and stored in a 2 Gbyte on-board flash-eprom memory. A telemetry channel using the Inmarsat satellite is used to control the experiment during the whole flight.