Technique for measurements of the evaporation rate of a heated liquid layer is presented. The local minimum is observed which is associated with the point of equilibrium of the liquid-gas interface. It is shown when no heat is applied to the heating element temperature in gas phase is larger than in liquid, and evaporation occurs with the rate of 0.014-0.018 μl/s. Then evaporation rate is decreasing with increasing the heater temperature until the equilibrium point is reached at the liquid-gas interface. Further increasing of the heater temperature leads to increasing of the evaporation rate.