In this paper, non-contact measurements are presented to observe droplet oscillations and to measure surface temperature during Pulsed GMAW. The techniques enable to investigate in situ the behavior of mild steel liquid metal surrounded by Ar + 8%CO2 plasma and then to measure temperature dependence of surface tension. Different temperatures are obtained by changing the process parameters. Surface tension values are a little higher than values found in the literature but the results demonstrate the interest of the developed setup. To conclude, a non-dimensional analysis is carried out, based on experimental results, to investigate the relative importance of the different phenomena acting during the transfer.