A new fully automated method for the accurate evaluation of the logarithmic decrement 6 in damped torsional oscillations is presented. The method is based on the measurement of time intervals between successive passages of an oscillating cup at a fixed position corresponding to an angular displacement 4 different from zero. The logarithmic decrement can be evaluated by means of a best-fit procedure from the dependence of the time interval upon 6 and T, T being the period of undamped motion.The method was tested by means of a torus-shaped crucible viscometer in a series of measurements of the viscosity of mercury at 19.2'C. The relative errors in the measurements were h TIT= 10-5 and A6jS = 1.25 x lo-*, representing an improvement, by a facor of about 10, on the best measurements reported in the literature for both the factors. The measured viscosity of the mercury was also in excellent agreement with previously published data.