In this communication, we report a technique to estimate the plasma parameters from the discharge characteristics of a microplasma device, operated in atmospheric pressure on the basis of homogeneous discharge model. By this technique, we investigate the plasma parameters of a microplasma jet produced by microplasma device consisting of coaxial capillary electrodes surrounded by dielectric tube. Our results suggest that the complex dependence of electrical discharge characteristics observed for microplasma device operated with Ar or it admixtures probably signify the existence of step ionization, which is well known in inductively coupled plasma. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729339]