A system and method for packaging a magnetic sensor is described. The reflected intensities from the two spots are detected and measured by one or two detectors. The adsorption dryer is characterized in that the cover, the cartridge casing and the base of the cartridges can each be secured in place with respect to one another via the central pipe, the central pipe in each case projects out of the cartridge and serves as a connecting means for the control head, and the cartridge itself is of compression-resistant design. An attention metric is generated for one or more attendees based on the first data and second data.