Care is required when choosing a flow meter for an application involving high viscosity liquids such as fuels and oils. In particular, the use of a flow meter that has been calibrated for water can cause large errors if the same meter is used for liquids with higher viscosity. It is also important to know what effect a change in temperature will have on fluid viscosity. Viscosity-compensated flow meters are insensitive to a wide variety of viscosities but they do have limits. Flow meters are insensitive to viscosity if the flow technology relies on some static property of the fluid, like conductivity, incompressibility or heat capacity. For example, the oval gear flow meter employs the property of near incompressibility of liquids to remain insensitive to changes in viscosity.
Typical viscous liquid flow applications include: monitoring of syrup injections in beverage lines; monitoring batch volumes of confectionery coatings; automated dispensing of cooking oils; engine and component development, testing and efficiency optimisation; determination of net fuel consumption; measuring fuel transfer rates; dosage and metering of fuel additives; leakage monitoring; lubricating oil monitoring; hydraulic fluid flow sensing in blow-out prevention; fiscal or custody transfer metering.