This thesis contains a numerical and experimental modal analysis of a rotary encoder produced by the company RLS Merilna Tehnika d.o.o. Encoder consists of a reading head, which detects the signal, and a ring with the feromagnetic rubber, which emitts the signal. Encoder uses Hall sensors for operating, hence the distance between module and ring is a crucial parameter. If this distance is too great, loss of signal occurs and consequently encoder cannot read the signals. Numerical model was established in Comsol software. Measurements were conducted in chambers and with equipment of the laboratory LADISK. It was established, that numerical model represents behaviour of a real encoder very good.