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.
Further, consider a Mass M moving from the center to the edge of a rotating plate.
This Mass M will take path B as shown below
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 as shown below
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.
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 consider the diagram below. The baseline deflection of the tubes from the Driver is shown by the blue trend and the Coriolis Twist from the Pickup Coil is designated by the red trend.
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;
Where,
| M Ac Ae Ac/Ae Sk Sk(20°C) | = Mass flow rate = Amplitude of coriolis oscillation = Amplitude of excitation oscillation = Phase Angle = Sensor constant (calibration constant) = Sk(20°C) (1+Skt x (T-20°C)) temperature correction = Sensor constant at 20°C = Excitation frequency = Temperature correction coefficient (material constant) |
The Density equation for the RotaMASS can be described as follows;
| p fI(20) fv(20) KD fv(20) FKT | = Density = Exciting frequency of the empty tubes at 20°C = Exciting frequency of the filled tubes at 20°C = Density calibration constant = fv / (1+FKT (T – 20 °C)) temperature correction of the actual frequency = Temperature correction coefficient, depending on material and size |
