System: Made by TA Instruments, the AR2000 can subject a fluid to the full range of shearing motions: steady, oscillatory, startup and cessation.  Hence the instrument can measure:

• Viscosity, as a function of shear rate (the flow curve)

• Dynamic properties, the shear modulus G’ and the storage modulus G”

• First Normal Stress Difference N1

• By such measurements, the viscoelasticity of a liquid can as evaluated

The rheometer can be operated in the controlled shear rate mode, where the shear rate is fixed and the required torque is measured, or in the controlled shear stress mode, where the shear stress is applied, and the resulting shear rate is measured.  In fact, the latter mode is a feature of the instrument, enabling the yield stress to be determined for pastes such as ketchup and mine tailings.  A variety of fixtures are available, enabling the rheometer to measure a wide range of viscosities, from watery liquids to polymer melts.  Moreover, an oven surrounds the test sample so that, along with a Peltier plate, tests can be conducted over a wide range of temperatures.

The AR2000 specifications (from TA Instruments):

• Temperature: from –20°C to 600°C

• Shear rate range: from 10^-4 s^-1 to 10^4 s^-1

• Viscosity range: from 5 mPa.s to 10^4 Pa.s