Until recently, most of electrical arcs applications were dealing with the properties of the centre of the plasma column, a large number of works was then done to develop diagnostic techniques dedicated to those area where the mean temperature is about 10000 K. With the emergence of plasma chemistery, the diagnostic of arc’s peripheral areas and un-equilibrium discharges become a goal of prime importance. Classical diagnostic techniques are not adapted to those objects where the maximum temperature is around 8000 K; the principal aim of this work was to develop and check diagnostic techniques. Two inovating techniques based on refractive index, the quantitative shadowgraphy and the moiré deflectometry were studied extensively and checked on a laminar plasma jet, a perfect model of arc’s peripheral area. To probe unequilibrium discharge, the use of UV OH spectrum was considered. At this occasion, a spectrum simulation software was written. The study of synthetic spectra lead to the creation of simple measurement methods of rotationnal and vibrationnal OH temperature for a large range of resolution. Those methods was checked on a low power electric discharge. It can be shown that result from molecular spectroscopy are close to those obtained by simulation.
