Magnet Coil Drive Circuits - ABB 10DX3111G Instruction Manual

This may be expressed mathematically as -
(Equation #1)
where:
E = induced electrode voltage
s
B = magnetic field strength
D = meter pipe diameter
∝ = dimensionless constant
V = fluid velocity
Thus, the metered fluid constitutes a continuous series of conductive fluid disks moving through a
magnetic field. The more rapid the rate of fluid flow, the greater the instantaneous value of signal
voltage as monitored at the meter electrodes.

3.1.2 Magnet Coil Drive Circuits

In most conventional Magnetic Flowmeters the integral magnet coils are driven directly by the cus-
tomer's 50/60 Hz power service. Notably, however, the design of the ABB Instrumentation Series
10DX3111 Magnetic Flowmeter uses magnet drive circuits which are alternately energized bi-direc-
tionally at a low frequency rate as commanded by the associated Converter/Driver assembly.
3.1.3 Volumetric Flow Rate Measurement
The ABB Instrumentation Magnetic Flow Rate Measurement is a volumetric flow rate measuring in-
strument. This can be shown by substituting the physical equivalent of fluid velocity into equation
#1 as follows:
(Equation #2)
Substituting for V in equation #1
and solving for Q:
Since B = β E
r
and since ∝, D and β' are constant:
3-2
10DX3111 INSTRUCTION MANUAL
E = 1 BDV
s
∝
Q = 4Q
V =
2
πD
A
E 1 BD 4Q
s
=
2
∝ πD
∴ Q = π∝D
• E
s
4 B