Abstract In electrorotation digital generators of rotating electric fields producing various pulse shapes are used widely. The available theory however, allows only for monochromatic fields. It is shown how to recalculate experimental data in order to apply the theory of electrorotation. As an example, square-topped fields are analyzed. The result is that in square-topped fields the electrorotation spectrum is shifted as a function of the key ratio. Furthermore, in order to eliminate the uncertainty of not knowing precisely hydrodynamic friction of the particle under consideration, a special numerical procedure was introduced. It compared the slope of the experimental curve near the zero point of rotation with the heights of the rotation peaks.