Flow Meter Cheat Sheet

Learn about the strengths and liabilities of different types of flow meters. Information courtesy of previous Pumps & Systems articles, primarily by Badger Meter and Ray Hardee

Differential Pressure
Pros

• well understood
• no moving parts
• not greatly affected by viscosity changes

Cons

• limited accuracy and turndown
• complex installation requirements

Coriolis
Pros

• handles viscous or difficult fluids that don’t work well with other measurement technologies
• no internal moving parts
• minimum upkeep once installed

Cons

• expense
• sometimes considered too sophisticated

Electromagnetic
Pros

• no moving parts
• low pressure drop
• high accuracy
• can handle range of viscosity, temperature and pressure

Cons

• tendency to foul
• heavy weight
• expense

Positive Displacement (PD)
Pros

• highly accurate
• easy to maintain
• does not require straight pipe lengths

Cons

• only clean fluids
• large size
• difficult to install

Thermal Mass
Pros

• low purchase cost
• works well with gases

Cons

• low to medium accuracy

Turbine
Pros

• high accuracy
• wide turndown
• repeatable measurements

Cons

• only clean fluids
• requires recalibration and service

Impeller
Pros

• universal mounting
• relatively low cost

Cons

• only clean, low-viscosity fluids
• requires higher fluid velocity

Ultrasonic
Pros

• can be used with corrosive fluids or gases
• unaffected by changes in temperature, viscosity, density or pressure

Cons

• much less dependable at low flow rates
• sensitive to unknown piping variables

Variable Area
Pros

• simple
• inexpensive
• reliable

Cons

• must be mounted perfectly vertical
• needs to be calibrated
• relatively low accuracy

Vortex
Pros

• no moving parts
• no regular maintenance

Cons

• only clean liquids
• may introduce pressure drop