Add to ORKGA new measurement system able to detect the occurrence of arcing between the pantograph and the overhead contact line has been studied and set up. It uses photomultiplier tubes in order to measure the duration of the ultraviolet emission due to electrical arcing. The measurement equipment was installed on board of an ETR500, a high-speed train of Italian Railways, with a double pantograph. A software package was developed in LabWindows/CVI environment for recording and elaborating data acquired from the measurement chain. In the paper the software for acquiring and processing data in order to validate the phototube sensor and to evaluate the status of the pantograph-catenary interaction is presented, along with experimental results