A method for determining the effective distance of electrical potential probes in the temperature field of a sample having a prismatic geometry, comprising a thermoelectric material, wherein said sample has two spatially separated contact surfaces, and the distance between these contact surfaces corresponds to the length I, comprising: a) contacting a first contact surface of the sample through a first contact material with a first block, and b) contacting a second contact surface of the sample through a second contact material with a second block, wherein said first block and said second block comprise a metal and/or a metallic coating, said metal and/or metallic coating having a Seebeck coefficient whose absolute value is 10 μV/K or less, c) applying at least one electrical potential probe each to said first block and said second block so that these probes have electrically conductive connections through the respective block (2a, 2b) to the respective contact material (3a, 3b), d) applying at least two electrical potential probes to the sample, wherein the distance in the direction of the block distance between the probes is I p, and I p < I, wherein the potential probes on the sample and the potential probes on the blocks (2a, 2b) essentially consist of the same material, and the applying is effected in such a way that no electric current or heat can flow into or from the sample through the probes during the subsequent measurement, followed by e) setting a temperature difference ΔT between the first block and the second block, f) determining the thermovoltage V 1 between the first block and the second block by means of the probes respectively applied to the blocks, g) subsequently or simultaneously with f) and under the same temperature conditions as in step f), determining a thermovoltage V p by means of the electrical potential probes applied to the sample, and h) forming the ratio V p /V 1, and forming of the length ratio I p /I from the ratio V p /V 1, wherein the length ratio I p /I corresponds to the effective distance between the electrical potential probes on the sample. a) contacting a first contact surface of the sample through a first contact material with a first block, and b) contacting a second contact surface of the sample through a second contact material with a second block, wherein said first block and said second block comprise a metal and/or a metallic coating, said metal and/or metallic coating having a Seebeck coefficient whose absolute value is 10 μV/K or less, c) applying at least one electrical potential probe each to said first block and said second block so that these probes have electrically conductive connections through the respective block (2a, 2b) to the respective contact material (3a, 3b), d) applying at least two electrical potential probes to the sample, wherein the distance in the direction of the block distance between the probes is I p, and I p < I, wherein the potential probes on the sample and the potential probes on the blocks (2a, 2b) essentially consist of the same material, and the applying is effected in such a way that no electric current or heat can flow into or from the sample through the probes during the subsequent measurement, followed by e) setting a temperature difference ΔT between the first block and the second block, f) determining the thermovoltage V 1 between the first block and the second block by means of the probes respectively applied to the blocks, g) subsequently or simultaneously with f) and under the same temperature conditions as in step f), determining a thermovoltage V p by means of the electrical potential probes applied to the sample, and h) forming the ratio V p /V 1, and forming of the length ratio I p /I from the ratio V p /V 1, wherein the length ratio I p /I corresponds to the effective distance between the electrical potential probes on the sample.