Abstract: The present invention describes a control device for determining an actual fuel turnover for a fuel cell arrangement comprising a voltage reception device for receiving values of a voltage applying over the fuel cell arrangement, a fuel flow setting device for setting a flow of fuel supplied or suppliable to a fuel cell arrangement and/or a current setting device for setting an electrical current output by the fuel cell arrangement, as well as a memory for storing calibration data describing a nominal relation between the fuel turnover of the fuel cell arrangement and a voltage applying over the fuel cell arrangement. The control device is adapted to receive a first voltage value; to control a variation of the flow of fuel supplied to the fuel cell arrangement and/or the current output by the fuel cell arrangement after receiving the first voltage value; and to receive a second voltage value after the variation.