A multilevel generator has been developed based on a gradient magnetic field source using square Helmholtz coils, which makes it possible to create changes in the level of the magnetic field in the horizontal plane with a constant vertical magnetic component. The error in setting the generated magnetic field can reach 4 %, which is comparable to natural fluctuations of the Earth's magnetic field. The generator provides experiments with biological objects in the working area of square Helmholtz coils with a volume of at least 0.25 m3, reducing the experiment time by more than five times. The developed design options for a multilevel generator make it possible to conduct a variety of magnetobiological experiments: in a uniform and gradient magnetic field, with magnetic field inversion and transition through the zero value, in combined magnetic fields.