Chapter 2 Introduction
www.supmea.com
2.2. Measuring principle
The operating principle of electromagnetic flowmeter is based on Faraday's law of
electromagnetic induction. The two electromagnetic coils at the upper and lower
ends as shown in Figure 3 generate a constant or alternating magnetic field. When
the conductive medium flows through the electromagnetic flowmeter, the induced
electromotive force can be detected between the left and right electrodes on the
wall of the flowmeter tube. The magnitude of the induced electromotive force is
proportional to the electrically conductive medium flow rate, the magnetic induction
density of the magnetic field, and the width of the conductor (the inner diameter of
the flowmeter measuring tube), and the flow rate of the medium can be obtained by
calculation. The induced electromotive force equation is as follows:
E=K×B×V×D
Where: E－Induced electromotive force
K－Meter constant
B－Magnetic induction density
V－Average flow speed in cross-section of measuring tube
D－Inner diameter of measuring tube
Figure 3
When measuring the flow, the fluid flows through a magnetic field which is
perpendicular to the flow direction. The flow of conductive fluid induces a potential
proportional to the average flow velocity, thus requiring the conductivity of the
measured flowing liquid to be higher than the minimum conductivity (5us/cm).
The induced voltage signal is detected by two electrodes and transmitted to the
To Next Page
Loading...
Need help?
General
