High speed laboratory stirrer designed for intensive stirring tasks for quantities up to 20 l (H2O). It automatically adjusts the speed through microprocessor controlled technology within the speed range of 0/150 - 6000 rpm. Safety circuits installed ensures automatic cut-off in an anti-stall or overload conditions. Continuous comparison of shaft speed to desired speed is maintained and variations are adjusted automatically. This guarantees a constant speed even with changes in viscosities of the sample.