According to the known method, a reference measurement is performed by measurement of magnetic resonance signals, without application of a magnetic gradient field to introduce phase encoding in the magnetic resonance signals. According to the invention, two measurements are performed with a read-out gradient of opposite polarity at substantially corresponding instants, relative to an instant at which the contributions to the phase error due to frequency deviations are zero. The advantage of the novel method resides in the fact that a higher insensitivity to field inhomogeneities and chemical shifts is achieved.