Proline Promass 80H, 83H
Hauser
3
Function and system design
Measuring principle
The measuring principle is based on the controlled generation of Coriolis forces. These forces are always present
when both translational and rotational movements are superimposed.
F
C
= 2 ·
Δ
m (v ·
ω
)
F
C
= Coriolis force
Δ
m = moving mass
ω
= rotational velocity
v = radial velocity in rotating or oscillating system
The amplitude of the Coriolis force depends on the moving mass
Δ
m, its velocity v in the system, and thus on
the mass flow. Instead of a constant angular velocity
ω
, the Promass sensor uses oscillation.
This causes the tube through which the fluid is flowing to oscillate. The Coriolis forces produced at the
measuring tubes cause a phase shift in the tube oscillations (see illustration):
• If there is zero flow, i.e. when the fluid stands still, the oscillation measured at points A and B has the same
phase, and thus there is no phase difference (1).
• Mass flow causes deceleration of the oscillation at the inlet of the tubes (2) and acceleration at the outlet (3).
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The phase difference (A-B) increases with increasing mass flow. Electrodynamic sensors register the tube
oscillations at the inlet and outlet.
For the Promass H, the system balance is created by a counterweight that runs parallel to the measuring tube.
This counterweight oscillates in antiphase to the measuring tubes and thus creates a balanced system. The
patented ITB™ (Intrinsic Tube Balance) system ensures balance and stability, thus providing accurate
measurements over a wide range of process and environmental conditions.
Therefore, the Promass H is just as easy to install as the familiar two-tube systems! Consequently, no special
measures for attachment are required in front of or behind the sensor.
The measuring principle operates independently of temperature, pressure, viscosity, conductivity and flow
profile.
Density measurement
The measuring tube is continuously excited at its resonance frequency. A change in the mass and thus the
density of the oscillating system (comprising the measuring tube and fluid) results in a corresponding, automatic
adjustment in the oscillation frequency. Resonance frequency is thus a function of fluid density. The
microprocessor utilizes this relationship to obtain a density signal.
Temperature measurement
The temperature of the measuring tube is determined in order to calculate the compensation factor due to
temperature effects. This signal corresponds to the process temperature and is also available as an output.
1
2
3
A
B
A
B
A
B
