QUIZ CORNER: Which Flowmeters Measure Velocity?
Which of the following flowmeters measure the velocity of the fluid passing through the flowmeter?
A. Coriolis mass
B. Magnetic
C. Orifice plate
D. Oscillating piston
E. Oval gear
F. Thermal
G. Turbine
H. Venturi
I. Vortex shedder
Commentary
Positive-displacement flowmeters that constantly entrap fluid to measure the actual volume were discussed last month. Oscillating piston and oval gear flowmeters are examples of positive displacement flowmeters.
Various technologies can be used to measure fluid velocity. For example, magnetic flowmeters measure the velocity with which a conductive fluid traverses a magnetic field. Turbine flowmeters measure the velocity with which the fluid passes a turbine. Vortex shedding flowmeters measure the velocity with which the fluid passes the shedder bar.
The correct answers are Answer B, G and I.
READ ALSO: MAGNETIC FLOWMETERS: Suited for Many Challenging Liquid Measurements
Additional Complicating Factors
From an academic perspective, flowmeters that measure the fluid velocity should display in velocity units of measurement. This is generally not done because knowing the fluid velocity without knowing the pipe size is effectively useless. For example, knowing that the velocity in a pipe is 2 meters per second is useless without knowing the inside pipe diameter. It is also complicated because calculations are required to determine the quantity of flowing fluid in useful units (such as kilograms or liters).
Therefore, most flowmeters that measure fluid velocity display in volumetric or mass units of measurement.
David W. Spitzer is a regular contributor to Flow Control magazine and a principal in Spitzer and Boyes, LLC offering engineering, seminars, strategic, marketing consulting, distribution consulting and expert witness services for manufacturing and automation companies. Spitzer and Boyes is also the publisher of the Industrial Automation Insider. David has more than 35 years of experience and has written over 10 books and 300 articles about flow measurement, instrumentation and process control.
David can be reached at 845 623-1830 or www.spitzerandboyes.com. Click on the “Products” tab to find his Consumer Guides to various flow and level measurement technologies.
