Pressure drop for flow through a rotameter is medium. Some other types of pipe flow meter have lower pressure drop and some cause a higher pressure drop than a rotameter.
The effect of fluid viscosity on the operation of a rotameter for pipe flow measurement is medium. The effect of fluid viscosity is less for some types of pipe flow meter and it is greater for some.
The typical turndown ratio for a rotameter is 10:1, that is: a flow rate as low as one tenth of the full scale reading can be measured accurately. This mid-range for flow meter turndown ratio. Some types of flow meter have a higher typical turndown ratio and some have a lower value for this parameter.