Which type of flow measurement is most influenced by fluid viscosity?

Positive displacement meters are particularly sensitive to fluid viscosity because they operate by trapping a fixed amount of fluid in a chamber and then measuring the volume of fluid as it passes through the meter. The mechanical components of these meters rely on the ability to move freely and consistently with the fluid.

High viscosity fluids can create more resistance to flow, potentially leading to reduced accuracy or flow measurements if the fluid is too thick. The precise functioning of positive displacement meters means that variations in viscosity can substantially alter performance, resulting in discrepancies in the volume of fluid measured. As such, they are designed to provide accurate measurements even for varying fluid viscosities, but their effectiveness can be diminished when the viscosity strays significantly from the range for which they are calibrated.

In contrast, other flow measurement technologies, such as magnetic flow meters, turbine flow meters, and vortex flow meters, either do not rely on the fluid's viscosity in the same way or have specific operational designs that allow them to mitigate the effects of viscosity changes. For example, magnetic flow meters are unaffected by viscosity since they measure the velocity of conductive fluids based on electromagnetic principles, while turbine and vortex meters use fluid dynamics to measure flow rates, which are less sensitive to viscosity but still impacted under extreme conditions.