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Process/Instrument Suitability of Flowmeters
Flow measurement technology 
Operating principle  Linearity 
2way flow 
Differential pressure 
Fluid mass selfacceleration, potentialkinetic energy exchange 

(some) 
Laminar  Viscous fluid friction  linear  yes 
Weirs & flumes 
Fluid mass selfacceleration, potentialkinetic energy exchange 
Hn  no 
Turbine (velocity) 
Fluid velocity spinning a vaned wheel 
linear  yes 
Vortex  von K´arm´an effect  linear  no 
Magnetic  Electromagnetic induction  linear  yes 
Ultrasonic  Sound wave timeofflight  linear  yes 
Coriolis  Fluid inertia, Coriolis effect  linear  yes 
Turbine (mass)  Fluid inertia  linear  (some) 
Thermal 
Convective cooling, specific heat of fluid 
linear  no 
Positive displacement  Movement of fixed volumes  linear  (some) 
A potentially important factor in choosing an appropriate flowmeter technology is energy loss caused by pressure drop. Some flowmeter designs, such as the common orifice plate, are inexpensive to install but carry a high price in terms of the energy lost in permanent pressure drop (the total, nonrecoverable loss in pressure from the inlet of the device to the outlet, not the temporary pressure difference between inlet and vena contracta). Energy costs money, and so industrial facilities would be wise to consider the longterm cost of a flowmeter before settling on the one that is cheapest to install. It could very well be, for example, that an expensive venturi tube will cost less after years of operation than a cheap orifice plate1.
In this regard, certain flowmeters stand above the rest: those with obstructionless flowtubes. Magnetic and ultrasonic flowmeters have no obstructions whatsoever in the path of the flow. This translates to (nearly) zero permanent pressure loss along the length of the tube, and therefore. Thermal mass and straighttube Coriolis flowmeters are nearly obstructionless, while vortex and turbine meters are only slightly worse.
1This is not always the case, as primary elements are often found on throttled process lines. In such cases where a control valve normally throttles the flow rate, any energy dissipated by the orifice plate is simply less energy that the valve would otherwise be required to dissipate. Therefore, the presence or absence of an orifice plate has no net impact on energy dissipation when used on a process flow throttled by a control valve, and therefore does not affect cost over time due to energy loss.
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