Is viscosity measurement affected by flow rate? 

Is there a recommended flow rate for measurement?

SRV is not affected by flow rate, it can measure at static or dynamic conditions so there is no recommended flow rate for any material from the sensor's perspective.

However, most fluids are non-Newtonian and hece are shear sensitive. Whether these fluids are flowing fast or slow (pumped) will lead to difference in apparent viscosity which is measured by the SRV and the sensor will show a difference in viscosity depending on the flow rate.

So what to do?

You want to start with a low flow rate and gradually ramp up the flow rate. You will see viscosity will change. However keep an eye that whether the temperature is changing as well? You want the temperature to stay constant and only flow rate to change. Either ensure constant temperature of operation or use temperature compensation for viscosity.

As you ramp up the flow rate you will see that the change in viscosity (slope of the viscosity vs flow rate curve) will start flattening, that is, beyond a certain flow rate there is little influence of the flow rate on the fluid shear thinning or thickening.

You want to operate the pump/flow rate in this almost flat (low slope) part of the curve.

References

Read the article from the science desk at rheonics on demystifying non-Newtonian fluid measurements

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