ELIS PLZEŇ a. s.
Project design, installation and service manual
Page 5 of 72
Electromagnetic flowmeter FLONET FH30xx
ELIS PLZE
Ň a. s., Luční 425/15, 301 00 Plzeň, Czech Republic, phone.: +420 377 517 711, fax: +420 377 517 722
Es 90678K
1 BASIC INFORMATION
1.1
Application
FLONET FH30xx is an electromagnetic flowmeter intended for measurement of volume flow rate of
electrically conductive liquids in closed piping. The meter facilitates high-accuracy bi-directional flow
rate measurements at flow velocities ranging from 0.025 to 10 m/s. The minimum required conductivity
of the measured flui
d is 10 μS/cm, for de-mineralised water it is 20 μS/cm.
1.2. Measurement principle
The function of electromagnetic flowmeter is based on the Faraday induction law. The meter sensor
consists of a non-magnetic electrically non-conductive tube and two inbuilt electrodes that pick up the
induced voltage in a plane perpendicular to the direction of the magnetic power lines. The magnetic field
is generated by electric current flowing through two coils wound on the tube. The flow of the conductive
liquid through the tube gives rise to induced voltage
U
proportional to the magnetic flux density
B
, flow
velocity
v
and the length of the virtual conductor
l
:
U = B × l × v
U
induced voltage
B
flux density
l
distance between the measuring electrodes
v
flow velocity of the measured liquid
For the given sensor size, the values of flux density and distance between electrodes are constant.
Therefore, the voltage induced on the electrodes is proportional to the velocity of the liquid flowing
through the sensor tube. The volume flow rate is then the product of the liquid flow velocity and the tube
cross-section:
Q = v
× S
.
