You can use the Boltzmann plot or the ratio of two line-intensities.

Both methods are described very accurately in:

J. S. Cowpe, Optical Emission and Mass Spectrometric Diagnostics of Laser-Induced Plasmas, Doctoral Thesis 2008

Boltzmann plot give excitation temperature (T_exc). DBDs are far away from LTE, therefore relation between T_exc and electron temperature (T_e) is not obvious. There is no standard solutions.

You may get some help from Park et al., "Electron density and temperature measurement by continuum radiation emitted from weakly ionized atmospheric pressure plasmas", Appl. Phys. Lett. 104, 084103 (2014).

i think this article may help you. 

Article Diagnostics of average temperature fields and electron densi...

you can use modified boltzmann plot or line intensity ratio method. But i suggest you to use modified boltzmann plot method for the estimation of excitation temperature