Omkar_Walambe_New_Animation_For_Coriolis_Mass_Flowmeter

A mass flow meter, also known as an inertial flow meter is a device that measures mass flow rate of a fluid traveling through a tube. The mass flow rate is the mass of the fluid traveling past a fixed point per unit time.
The mass flow meter does not measure the volume per unit time (e.g., cubic meters per second) passing through the device; it measures the mass per unit time (e.g., kilograms per second) flowing through the device. Volumetric flow rate is the mass flow rate divided by the fluid density. If the density is constant, then the relationship is simple. If the fluid has varying density, then the relationship is not simple. The density of the fluid may change with temperature, pressure, or composition, for example. The fluid may also be a combination of phases such as a fluid with entrained bubbles.

Operating principle of a coriolis flow meter
There are two basic configurations of coriolis flow meter: the curved tube flow meter and the straight tube flow meter. This article discusses the curved tube design.

A rotating mass flow meter to illustrate the operating principle of the vibrating mass flow meter.
double sized version

When fluid is flowing through the tubes, the tubes twist slightly.
double sized version
The animations on the right do not represent an actually existing coriolis flow meter design. The purpose of the animations is to illustrate the operating principle, and to show the connection with rotation.
Fluid is being pumped through the mass flow meter. When there is mass flow, the tube twists slightly. The arm through which fluid flows away from the axis of rotation must exert a force on the fluid, to increase its angular momentum, so it bends backwards. The arm through which fluid is pushed back to the axis of rotation must exert a force on the fluid to decrease the fluid's angular momentum again, hence that arm will bend forward.
In other words, the inlet arm is lagging behind the overall rotation, and the outlet arm leads the overall rotation.

The principle design of a curved tube mass flow meter. The vibration pattern during no-flow.
double sized version
The animation on the right represents how curved tube mass flow meters are designed. When the fluid is flowing, it is led through two parallel tubes. An actuator (not shown) induces a vibration of the tubes. The two parallel tubes are counter-vibrating, to make the measuring device less sensitive to outside vibrations. The actual frequency of the vibration depends on the size of the mass flow meter, and ranges from 80 to 1000 vibrations per second. The amplitude of the vibration is too small to be seen, but it can be felt by touch.
When no fluid is flowing, the vibration of the two tubes is symmetrical, as shown in the animations.