Measuring principle: When a mass flows through a vibrating pipe Coriolis forces exist
which bend or twist the pipe. These very small meter tube distortions are measured by
optimally located sensors and evaluated electronically. Since the measured phase shift
between the sensor signals is proportional to the mass flow rate, the mass flow rate
through the Coriolis mass flowmeter can be determined directly.
This measuring principle is independent of density, temperature, viscosity, pressure
and conductivity. The meter tubes always vibrate at resonance. The resonant frequency
which exists is a function of the meter tube geometry, the material properties and
the mass of the measuring medium vibrating in the meter tube. It provides exact information
about the density of the medium to be measured. In summary, it can be stated
that the Coriolis mass flowmeter can be used to simultaneously measure the mass flow
rate, density and temperature of a measuring medium.
Advantages of this Measurement Method:
• Universal measuring system for flow rate, density and temperature, independent of
– conductivity
– inlet and outlet sections
– flow profile
– density and, thus, pressure and temperature of the measuring medium
• Direct mass flow measurement
• Very high measuring accuracy (typically ± 0.15 % of rate)
• Multi-variable measuring principle, simultaneous measurement of
– mass flow rate
– volume flow rate
– density
– temperature
• No moving parts, therefore wear free
Disadvantages of this Measurement Method:
• Relatively high initial cost (for an accuracy of 0.15 % of rate)
• Installation limitations for multi-phase measuring media or high gas content
• Deposits or abrasion can lead to errors, especially in the density measurement
• Limited material selections for process wetted parts, corrosion resistance must be
checked