Magnetic 2.5L two-speed stirrer with tachometer, stainless steel cover, 110/115V, The HI 302N model can stir up to 2.5 liters (0.66 gallons). It is often desirable to stir your samples in two directions. This will achieve maximum homogeneity and solubility. An advanced circuit allows HI 302N to reverse the direction of the stirring at a user selected interval. The interval can be adjusted from 30 seconds up to 3 minutes.
In addition to precision speed control, a limiter will also assure that the maximum speed will never be exceeded. During repeated testing, samples are often removed from the stirrer before the speed is reduced. This could cause the motor to accelerate until it destroys itself. HANNA stirrers incorporate a VCO device that stops the motor from accelerating as soon as the load is removed (Speedsafe).