Function And System Design; Measuring Principle - Endress+Hauser Proline Promass I 100 Technical Information

Proline Promass I 100

Measuring principle

Endress+Hauser
Symbol Meaning
Hazardous area
-
Indicates a hazardous area.
Safe area (non-hazardous area)
.
Indicates the non-hazardous area.

Function and system design

The measuring principle is based on the controlled generation of Coriolis forces. These forces are
always present in a system when both translational and rotational movements are superimposed.
F = 2 · ∆m ( · ω)
c
F = Coriolis force
c
∆m = moving mass
ω = rotational velocity
= radial velocity in rotating or oscillating system
The amplitude of the Coriolis force depends on the moving mass ∆m, its velocity in the system and
thus on the mass flow. Instead of a constant rotational velocity ω, the sensor uses oscillation.
In the sensor, an oscillation is produced in the measuring tube. The Coriolis forces produced at the
measuring tube 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 (no phase difference).
• Mass flow causes deceleration of the oscillation at the inlet of the tubes (2) and acceleration at the
outlet (3).
1
The phase difference (A-B) increases with increasing mass flow. Electrodynamic sensors register the
tube oscillations at the inlet and outlet. System balance is created by exciting an eccentrically
arranged swinging mass to antiphase oscillation. 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 measuring tube and fluid) results in a
corresponding, automatic adjustment in the oscillation frequency. Resonance frequency is thus a
function of medium density. The microprocessor utilizes this relationship to obtain a density signal.
Volume measurement
Together with the measured mass flow, this is used to calculate the volume flow.
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 signal.
2 3
A0016772
5