Function And System Design; Measuring Principle; Measuring System - Endress+Hauser Proline Promass E 100 Manual

Proline Promass E 100

Measuring principle

Measuring system

Endress+Hauser
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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 (ν · ω)
c
F = Coriolis force
c
∆m = moving mass
ω = rotational velocity
ν = radial velocity in rotating or oscillating system
The amplitude of the Coriolis force depends on the moving mass ∆m, its velocity ν in the system and
thus on the mass flow. Instead of a constant rotational velocity ω, the sensor uses oscillation.
In the sensor, two parallel measuring tubes containing flowing fluid oscillate in antiphase, acting like
a tuning fork. The Coriolis forces produced at the measuring tubes cause a phase shift in the tube
oscillations (see illustration):
• At zero flow (when the fluid is at a standstill) the two tubes oscillate in phase (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. System balance is ensured by the antiphase oscillation of the
two measuring tubes. 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.
The device consists of a transmitter and a sensor. If a device with Modbus RS485 intrinsically safe is
ordered, the Safety Barrier Promass 100 is part of the scope of supply and must be implemented to
operate the device.
The device is available as a compact version:
The transmitter and sensor form a mechanical unit.
2 3
A0028850
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