Fluctuation enhanced sensing (FES) is a promising method to improve information extraction from noisy sensor signal especially in the rapidly growing field of semiconductor and nanotechnology gas sensors. Some attempts were made to support the application of the principle in low power, battery powered devices and partial results are available. In this paper we present a complete mixed-signal system that contains a low power analog and digital signal processing part as well. Besides theoretical investigations we have carried out measurements and simulations to optimize the performance and achieve high accuracy. Including all components and processing the system needs only 2mA of active supply current working from a 3V battery and a coin cell battery can provide 250 days of operation at sample rate of 6 samples per hour.