This paper describes the implementation of an automatic measuring system used to acquire the voltage drop from a gradually heated TEG output with and without load. This will help determine the Seebeck coefficient and the internal resistance of the thermo electrical generator. The Seebeck coefficient is one of the TEGs main characteristic and gives valuable information about the output voltage the TEG can generate if its two sides are maintained at different temperatures. Some thermo electrical module (TEM) manufacturers give a constant Seebeck coefficient value for their products while measurements prove that in fact it is temperature dependent. The purpose of this research is to accurately investigate the Seebeck coefficient and internal resistance values depending on temperature and determine the TEMs performance. Using the experimental results we propose to later create an improved thermo electrical model for the TEG.