Rotational Viscometer Principle

  • They are amongst the most widely used meters.
  • The principle used behind this method involves torque required to rotate cylinder is dependent on viscosity of fluid.
  • They are classified as
    1)Cup bob (concentric cylinder) type
    2)Cone Plate type
  • Concentric cylinder assembly involves two cylinder one over other separated by liquid between them, one of them is kept static and other one rotates & generates torque.
  • Cone & plate assembly uses narrow angled cone with flat plate, shear stress & shear rate at given angular velocity gives viscosity.
  • Air gap due to bubbles might induce error.