David W. Spitzer
David W. Spitzer

Which of the following flowmeters measure the mass 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 already discussed. Oscillating piston and oval gear flowmeters are examples of positive displacement flowmeters. Flowmeters that measure velocity, such as magnetic, turbine, and vortex-shedding flowmeters were discussed last month.

READ ALSO: Which Flowmeters Measure Velocity?

Industrial Automation Insider 300x250 Coriolis mass flowmeters use the properties of mass to measure mass flow. Thermal flowmeters use the thermal properties of the fluid to measure mass flow. Accurate thermal flow measurement is predicated on the premise that the thermal properties of the fluid in a given application do not change appreciably with pressure, temperature and/or composition. The correct answer is Answers A and F.

Additional Complicating Factors
From an academic perspective, flowmeters that measure the mass flow should use mass units of measurement. This is often the case, but there are many installations where volumetric units are used. Converting the mass flow measurement to volumetric units typically entails assuming a constant fluid density. However, most Coriolis mass flowmeters can measure mass flow and density so they can calculate volumetric flow using the actual density 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 can be reached at 845 623-1830.

Mr. Spitzer 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.