The Coriolis principle in mass flow meters: Basics, applications and advantages
The Coriolis principle is related to movement – which is why we are also illustrating it with an example involving movement: Imagine that you are sitting on a rotating carousel and want to throw a ball to another person on the carousel. If you throw the ball in a straight line, it will not reach the person. Furthermore: From your perspective, it appears as if the ball is deflected by an invisible force. The reason for this is the Coriolis force. This example shows us that the Coriolis effect is a question of perception. Outside the rotating system, which in our example is outside the carousel, the ball flies straight ahead. From your perspective as the thrower, it is deflected and describes an arc.
The Coriolis force also plays a major role on Earth
The Coriolis principle also exists on Earth because the planet is turning and is thus also a rotating system. Although we do not feel this rotation, it nevertheless generates the Coriolis effect, which has a strong influence on our environment. For instance, the Coriolis force is responsible for weather phenomena such as hurricanes. It also affects the ocean currents or the magnetic field of our planet.
Did you also know that the Coriolis force determines the direction of rotation of hurricanes? In the northern hemisphere, they rotate clockwise. South of the equator, they rotate counter-clockwise.
But what exactly is the Coriolis force? And what does it have to do with the flow measurement of masses?
The basics of the Coriolis principle
What is the Coriolis effect and where does it come from?
If a body moves along the axis of rotation from a rotating system, the Coriolis force acts on it in addition to the centrifugal force. However, this only happens from the perspective of the observer who is inside the moving system. From an outside perspective, the object would still be moving straight ahead.
The law of inertia
The law of inertia according to Newton states that an object will remain in the same state if no external forces are acting upon it. This means that the body is either at rest or moving at a steady speed and in the same direction unless it is compelled by external forces to change its state or its direction of movement.
The Coriolis force
From a physical perspective, the Coriolis force is one of the forces of inertia that is also perceptible in addition to the centrifugal force if the object moves along the rotation axis. For observers, the object appears to be continuously accelerating. The Coriolis force was named after the French scientist Gaspard Gustave de Coriolis, who studied and analyzed it mathematically in 1835.
The Coriolis flow-measuring principle
The Coriolis principle can also be used for flow measurement. In this process, a tube is brought into vibration. This represents the rotating system referred to above. The axis of the disc corresponds to the suspension of the tube.
There are different variants of this measuring principle:
- with one tube
- with two parallel tubes
- with straight tubes
- with folded tubes
In the example, two tubes are arranged beside one another and secured at both ends (inlet and outlet). These tubes are excited by a pulse and thereby brought into vibration. In the absence of a flow, the vibration of the two tubes vibrate between the inlet and outlet is symmetric. The signal detected at the inlet is in phase with the signal at the outlet. This means that there is no phase displacement between them.
More medium = greater phase displacement
A flow will change the mass of the tubes, which results in a phase displacement between the two signals. In other words: The more medium that flows through, the greater is the phase displacement. This displacement changes in proportion to the mass flow of the medium flowing through the tubes.
Additional parameters: Change in resonant frequency
Since the Coriolis measuring principle is independent of thermodynamic parameters and only measures the pure mass, it can be applied to every fluid regardless of whether it is liquid or gaseous. It is also possible to measure the change in resonant frequency in addition to the phase displacement. The change is proportional to the density of the flowing medium and therefore provides an additional identifiable parameter. This makes it possible to determine the current volume flow.
Why and for what purpose is the flow rate measured?
The flow rate is suitable for precisely measuring the volume and mass of additives, for example. This establishes the basis for an optimized process flow.
What’s more, the flow rate can serve as a control function for valid hygiene regulations: The cleaning medium must flow at a specific speed through the pipeline to ensure optimum removal of the biofilm.
Where is the Coriolis principle applied?
As a general rule, this measuring principle can be used for measuring liquids, gases and vapors. Depending on the medium, different tubes are used for this purpose.
Alcohol Cleaning agents and solvents Vinegar Fruit solutions Oils and fuels Beer, milk
Water vapour
Liquefied gas (LPG) Methane
Coriolis technology can be used irrespective of the medium’s properties, which means that conductivity, density, viscosity etc. do not play a role here: Virtually all substances can be measured. The Coriolis principle can even be applied at high temperatures and in potentially explosive areas.
What advantages do Coriolis mass flow meters and controllers offer you when it comes to dosing?
What advantages do Coriolis mass flow meters and controllers offer you when it comes to dosing?
✓ High measuring accuracy is possible even with small flow measurements
✓ Universal measuring system for mass and density independent of:
- Conductivity (measurement also possible in liquids with poor conductivity e.g. de-ionized water)
- Density of medium
✓ Multivariable measuring principle, simultaneous measurement of:
- Mass flow
- Density
✓ Liquid only comes into contact with the tube
✓ No moving parts installed
As you can see, the Coriolis principle is quite astonishing. But what advantages does it offer you? The mass flow meters and controllers that make use of this principle allow you to enjoy exact, reliable and quick dosing. You can use them to optimize your dosing processes for any medium and product. The following solutions allow you to profit from these advantages. Learn more about the use of Coriolis mass flow meters and controllers for dosing the smallest amounts of liquid.
Coriolis mass flow meters and controllers
Mass flow meter MFM Type 8756 Mass flow controller MFC Type 8756 with micro annular gear pump
Learn more about our mass flow meters and mass flow controllers type 8756.
Mass flow controller (MFC)/mass flow meter (MFM) for liquids
- Flow measurement/control up to 120 kg/h
- Very high accuracy and measuring range
- High long-term stability, no zero-point adjustment necessary
- Highly resistant wetted materials
- Suitable for numerous liquids