The BF35 operates on a different measurement technique than traditional standard Brookfield Viscometers. The sample is placed in the cup and the spindle/chamber combination is then immersed into the sample. When the motor is turned on, the chamber rotates while the spindle remains stationary. When the dial reading becomes stable, the torque reading is recorded and manually converted into a viscosity value in centipoise. The BF35 maintains a constant shear rate and is an accurate and versatile tool for drilling fluid measurements. Motor Speeds - 8 fixed (3-6-30-60-100-200-300-600), Min. Viscosity - 0.5 cP (@600 rpm), Max. Viscosity - 10000000 (@0.01 rpm).