These quiet, economical overhead stirrers are suitable for simple laboratory mixing, in applications such as processing media with substantial temporary viscosity changes. Speed controls are infinitely adjustable, and safety circuits ensure automatic cutoff in anti-stall or overload conditions. Shaft speeds are constantly monitored with variations adjusted for automatically, guaranteeing a constant speed even with changes in sample viscosities. Stirrers are ergonomically designed with slim-profile casings and provide quiet operation. Digital displays relay speed and time.