3.0 PRINCIPLE OF OPERATION
3.1 Basic Operating Principle
3.1.1 Signal Voltage Generation
The operating principle of the ABB Instrumentation Model 10DX3111 Magnetic Flowmeter is based
upon Faraday’s Law of Induction which states that the voltage induced across any conductor as it
moves at right angles through a magnetic field will be proportional to the velocity of that conductor.
This principle finds common application in direct and alternating current generators. Essentially,
the ABB Instrumentation Magnetic Flowmeter constitutes a modified form of an ac generator.
Figure 3-1 graphically illustrates the basic operating principle. A magnetic field, "B", being gener-
ated in a plane which is perpendicular to the axis of the meter pipe. A disk of the metered fluid can
be considered as a conductor. The transverse length "D" is equal to the meter pipe diameter.
Since the velocity "V" of the fluid disk is directed along the axis of the meter pipe, a voltage, "E
s
",
will be induced within this fluid and is mutually perpendicular to the direction of the fluid velocity
and the flux linkages of the magnetic field; i.e., in the axial direction of the meter electrodes. This
electrode voltage is the summation of all incremental voltages developed within each fluid particle
that passes under the influence of the magnetic field.
FIGURE 3-1. BASIC OPERATING PRINCIPLE
10DX3111 INSTRUCTION MANUAL
3-1
