Hello Harini

I assume your measurement is based on the torque needed to rotate a disc.

The torque is proportional to the rotational speed and the area of the disc.

Therefore it means your torque meter is not sensitive enough. The full scale and resolution of your meter are in the order of the torque exerted by the fluid. There are two options to improve your measurement :1 using a bigger disc and 2 using a torque meter with higher resolution, namely, lower full scale value. the first option seems easier to get because the second one may mean a different equipment altogether.

Good luck

I assume you are measuring glycerol viscosity with the same set-up.

It's extremely difficult to cover large range of speed or torque with the same equipement. As said by Moshe, the torque mesaurement can no longer be reliable or the rotational speed no longer constant at very low values.

Anyway, glycerol is a Newtonian fluid and maybe results obtained at 1 rad/s and 10 rad/s are just sufficient to get a clear idea of its viscosity.

But take care to well control the sample temperature, glycerol viscosity is highly dependent upon T especially at room temperature.

Moshe Zilberman Philippe Vergne Thank you so much sir(s). I shall try using a bigger disc or use a different rheometer to ascertain the data.

Even though Glycerol is Newtonian, my concern lies in the fact that I won't be able to rely on any fluid's rheological data tested at 0.1 or 0.01 rad/s.

Thank you, again!

I have omitted a crucial point: glycerol is a highly hydrophilic fluid. It adsorbs water very easily. The consequence is that its viscosity changes a lot with its water content.

Therefore, in my opinion, it is not the ideal fluid to calibrate a rheological device, especially at very low rotational speed for which the test duration is rather long.