Alexandrovsky ancient settlement is situated in the Kaluga region near the river Voria and Alexandrovka village. Self potential (SP) measurements with new non-polarizing electrodes of the second generation instead of traditional copper-copper sulfate electrodes were performed in 2013 and increased the quality of measurements. SP data were analyzed together with electrical resistivity tomography (ERT). The authors found filtration SP anomalies and proved that the main SP anomaly has diffusion-adsorption origin, determined that the Alexandrovsky site of the ancient settlement has decreased SP values.