where Ω is the angular velocity of disk rotation and h is the distance between disks. The
variation of the shear rate throughout a volume of a sample being investigated is the main
disadvantage of this measuring device. However, if liquid being investigated possesses
Newtonian properties, then torque is proportional to the frequency of rotation, and viscosity
is calculated from a formula that is analogous in structure to that obtained for other
rotational instruments, namely: