KROHNE TIDALFLUX 4300 F EN - Manual (Page 29)

TECHNICAL DATA
7
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TIDALFLUX 4300 F
www.krohne.com 06/2010 - 4000970001 - TIDALFLUX 4300 F R01 en
7.1 Measuring principle
The TIDALFLUX 4000 is an electromagnetic flow sensor with an integrated capacitive level
measurement system, designed for electrically conductive process liquids. The flow rate Q(t)
through the tube is:
Q(t) = v(t) x A(t)
Q(t) = v(t) x A(t) Q(t) = v(t) x A(t) Q(t) = v(t) x A(t), in which
v(t) = Flow velocity of liquid product
A(t) = Wetted area of tube section.
The flow velocity is determined on basis of the known electromagnetic measurement principle.
The two measuring electrodes are located in the lower part of the measuring tube, on a level of
approx. 10% of the inner diameter of the pipe in order to get a reliable measurement to a level of
10%.
An electrically conductive fluid flows inside an electrically insulating pipe through a magnetic
field. This magnetic field is generated by a current, flowing through a pair of field coils. Inside of
the fluid, a voltage U is generated:
U = v * k * B * D
U = v * k * B * D U = v * k * B * D U = v * k * B * D
in which:
v = mean flow velocity
k = factor correcting for geometry
B = magnetic field strength
D = inner diameter of flow meter
The signal voltage U is picked off by electrodes and is proportional to the mean flow velocity v
and thus the flow rate q. The signal voltage is quite small (typically 1 mV at v = 3 m/s / 10 ft/s and
field coil power of 1 W). Finally, a signal converter is used to amplify the signal voltage, filter it
(separate from noise) and convert it into signals for totalising, recording and output processing.
Figure 7-1: Measuring principle TIDALFLUX
1 Electrodes
2 Induced voltage (proportional to flow velocity)
3 Capacitive plates in liner for height measurement
4 Magnetic field
5 Field coils