The IEC Centra 4B''s powerful series-wound motor offers rapid, smooth acceleration and can achive speeds to 12,000 RPM for microsample tubes; up to 11,000 RPM for 120 Ml (30ml x 4) and provides excellent speed/force characteristics for a wide range of sample loads up to 700 ml. An electronic dual range tachometer, a continuously-variable speed control and a precise 60 minute timer enable accurate setting and repeatability of run conditions. The Centra 4B control console is logically arranged and angled for easy use; push button controls illuminate for instant verification. Operator safety is assured by a positive interlock system which prevents the cover from opening until the rotor comes to a stop and the "Open Cover" indicator lights. Similarly, runs cannot be initiated until the cover latch is fully secured. For added protection of operator and instrument, an imbalance sensor automatically shuts off the unit if the sample load is not properly balanced. A panel indicator immediately alerts the operator. The electric brake provides a high initial braking torque which automatically decreases as the rotor decelerates assuring smooth even braking with no danger of sample resuspension. Further more the Centra 4B is compact, Rugged, and Easy to Clean!