Abstract
Polarimetry measurement results are used in tokamak plasma equilibrium codes as a constraint, decreasing the measurement uncertainty in determination plasma current, safety factor and density profile. In numerical codes, instead of solving rigorous equation of polarimetric state evolution, approximate analytical expression could be used to increase computing efficiency. In this paper is analyzed the precision of three different models compared with exact solution of polarization state evolution equation. Calculations are made for circular plasma model, with plasma parameters representative for operating domain of tokamak device. The obtained results define the limits of applicability of the separate proposed approximated methods in equilibrium codes for plasma in configuration similar to considered in the paper.