Introduction; Measurement Principle - Elis FLONET FN20xx.1 Series Design, Assembly And Service Manual

ELIS PLZEŇ a. s.

1. INTRODUCTION

The FLONET FN20xx.1 electromagnetic flowmeter has been designed to measure volume flow rates of
electrically conductive liquids in closed piping systems. The flow measurement can be carried out bi-
directionally, with a high measurement accuracy over a wide range of flow rates (0.1 to 10 m/s / 0.33 to 33
ft/s). The minimum required conductivity of the measured medium is 5 µS/cm.
The transmitter includes a two-line alphanumeric display to show the measured values where various
operating parameters of the meter can be selected on a keypad. The flowmeter has two passive binary
outputs, one active current output and an output to connect a digital communication line. All meter functions
and output parameters can be reset during the meter operation. If the meter is to be used as an invoicing
meter, some of its functions are blocked to prevent the user from interfering with the meter readings.
The user may combine any sensor of the IS X.xx type series with any transmitter (C 6.00 or C 7.00) without
re-calibration of the meter on a test stand (however, such calibration is required for invoicing meters). The
only thing that needs to be done is to enter the calibration constants and excitation frequency of the selected
sensor into the transmitter memory. These data are mentioned on the rating plate of the sensor. The value of
threshold flow rate shall be set between 0.5 and 1% of the specified maximum flow rate.

2. MEASUREMENT PRINCIPLE

The function of an electromagnetic flowmeter is based on Faraday's law of induction. The meter sensor
consists of a non-magnetic and non-conductive tube with two embedded measuring electrodes detecting the
induced voltage. The alternating magnetic field is created by two coils fitted onto the tube parallel to the
plane of the measuring electrodes. When a conductive liquid moves in a magnetic field B, voltage U will be
detected on the measuring electrodes. Such a voltage is proportional to the flow velocity v and the conductor
length l.
U = B x l x v
U induced voltage
B magnetic flux density
l distance between measuring electrodes
v liquid flow velocity
As the magnetic flux density and distance between the electrodes are constant, the induced voltage is
proportional to the liquid flow velocity in the tube. The value of the volume flow rate can then be determined
as a product of the flow velocity and square section of the tube, Q = v x S.
ELIS PLZEŇ a. s., Luční 425/15, 301 00 Plzeň, Czech Republic, Phone: +420/377 517 711, Fax: +420/377 517 722
Design, Assembly and Service Manual
Electromagnetic flowmeter FLONET FN20xx.1
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