Most (very) low shear rate measurements are performed in CS Mode, because most real live applications in which (very) low shear rates are important are driven by a constant stress.
Examples are sagging, sedimentation, shelf live, phase separation, all phenomena that are driven by a constant force i.e. gravitation.
These processes are simulated in a rheometer by applying a constant stress. However, under certain circumstances applying a (very) low shear-rate might be required, for example when the flow of material which is slowly stirred in a large container needs to be simulated (measured).
Haake Mars is capable of applying low rotational speed, i.e. low shear rates.
Reliable data down to n = 10-5 rpm
In the result of an experiment in which the rotational speed was stepwise increased from 10-5 rpm to 10-2 rpm, even at a low rotational speed (and a low torque) the measured viscosity is within 5% from the specified value.
Instrument: Haake Mars, UTC Peltier, PP35, gap = 0.5 mm. Sample: Newtonian Oil, = 175 Pas.
Haake Mars Accessory range or services are available from Rheology Solutions .