What is the Coriolis Principle?

To some of us the Coriolis Principle is an exact science, but to most of us it is still a black art. Well, imagine a fluid flowing (at velocity V) in a rotating elastic tube as shown below. The fluid will deflect the tube.

If the mass M is guided by Wall A (i.e. the tube), a Coriolis Force will be exerted on the wall as shown below.
CORIOLIS FORCE : Fc = -2 M V W
Now, consider the interior of the RotaMASS sensor
The tube walls guide the process fluid as it flows through the U-Tube pathway. With no fluid inside the tubes the Driver excites the tubes apart at a nominal 150Hz as shown below.
No Flow: Mass Flow:Coriolis Twist
Parallel Deflection

Now imagine fluid of Mass M flowing through and out of the RotaMASS tubes. As the fluid flows down the first half of the U-Tubes it will tend to deflect the tubes in towards each other. Conversely, when the fluid flows up the second half of the U-Tubes it will tend to deflect the tubes out away from each other. This Coriolis Twist action is shown above.

Now the temperature of these tubes dramatically affects their flexibility. So temperature measurement is very critical as follows.


The Mass flow equation for the RotaMASS can be described as follows.


p =Density
fI(20) = Exciting frequency of the empty tubes at 20°C
fv(20) = Exciting frequency of the filled tubes at 20°C
KD = Density calibration constant
fv(20) = fv / (1+FKT (T - 20 °C)) temperature correction
of the actual frequency
FKT = Temperature correction coefficient, depending
on material and size