A cartridge device having a receiving portion for receiving a blood sample and a jack portion for receiving a plug; a stirring device for circulating the blood sample within the receiving portion; and an electrode holder having at least one incorporated electrode wire pair; wherein the electrode holder is attachable to the cell such that one end of the at least one electrode wire pair forms a sensor unit for measuring the electrical impedance between the two electrode wires of the at least one electrode wire pair within the blood sample and that the opposite end of the at least one electrode wire pair forms a plug portion being connectable directly to the plug for an electrical connection of the sensor unit to an analyser.