The outer cylinder (sample cup) is driven by a stepper motor at speeds from 0.05 RPM to 1000 RPM. The inner cylinder (bob) contains an RTD probe on the surface to provide temperature measurement where the shear stress is being measured. Several cup and bob designs with different geometries are available to suit various applications.
The unique torque tube design enables the instrument to respond to minute changes in viscosity, mechanically transmitting a rotational torque signal out of the pressure containment area without friction. Thus all electronics, bearings, and other sensitive components are completely protected from the influences of both the sample fluid and its vapor.