The paper presents a rotational single sheet tester (RSST) which can be used to measure vector hysteresis characteristics inside a specimen with round shape. The measured hysteresis characteristics in the orthogonal directions presents uniaxial anisotropy. It has been handled by the Fourier expansion of the measured Everett functions. The Fourier coefficients of the unknown Everett function have been identified by the modification of a previously implemented algorithm. In the identification task linearly and circularly polarized measured data have been taken into account.