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Did you know? Coriolis

The Coriolis Effect

A bullet fired north from the South Pole will appear to be deflected to the left of the direction of fire while a bullet fired from the North Pole will be deflected to the right. This is due to the Coriolis effect, which explains the tendency of a moving body on the earth's surface to veer sideways due to the earth's rotation.

The reason for the deflection is because the earth's surface rotates towards the east at a greater speed near the equator than near the poles. (A point on the equator traces out a larger circle per day than a point on a latitude nearer either pole.)

Before it is fired, the bullet has a certain rotational speed and when fired towards the equator, the ground beneath it is moving at an increasingly higher rotational speed and so the bullet seems to be forced westward.

The Coriolis principle

The Coriolis principle is also used for direct measurement of mass flow. If a moving mass or fluid is subjected to an acceleration perpendicular to its direction of movement, Coriolis forces occur. These forces are directly proportionate to the momentum of the fluid, which is dependant on the mass flow.

Mass flow, density, temperature and viscosity


A Coriolis mass flow-meter utilises oscillating tubes to precisely measure this effect. A Coriolis flow-meter, such as Endress+Hauser's Promass, can provide simultaneous, direct measurement of mass flow, density, temperature and viscosity of virtually any fluid, independent of the physical fluid properties.

Highest Accuracy

Accuracy is extremely high (typically 0.1% o.r.). It is not affected by the flow profile and so has no requirement for upstream and downstream piping straight lengths, which is required by all other flow measurement principles.