Volumetric Flow Rate Measurement; Operating Characteristics; Liquid Variables; Liquid Conductivity - ABB MINI-MAG 10D1475 Instruction Manual

10D1475 MINI-MAG MAGNETIC FLOWMETER INSTRUCTION BULLETIN

1.2.1.3 Volumetric Flow Rate Measurement

The Bailey-Fischer & Porter Magnetic Flowmeter is a volumetric flow rate measuring instrument. This
can be shown by substituting the physical equivalent of liquid velocity into equation #1 as follows:
(Equation #2)
V =
Substituting for V in equation #1
E s = 1 BD
and solving for Q:
∴ Q = παD
Since B = β E
r
and since α, D and β are constant:
(Equation #3)
Q = γ E
where:
Q = volumetric flow rate
A = cross-sectional area
D = pipe section diameter
E = induced signal voltage
s
E = reference voltage
r
B = magnetic flux density
α = dimensionless constant
β & γ = dimensional constant
V = liquid velocity
Therefore, volumetric flow rate is directly proportional to the induced signal voltage as measured by
the Bailey-Fischer & Porter Magnetic Flowmeter.

1.2.2 Operating Characteristics

1.2.2.1 Liquid Variables

1.2.2.1.1 Liquid Conductivity

The Magnetic Flowmeter requires a liquid conductivity of 5 microsiemens per centimeter or higher for
operation. This minimum liquid conductivity requirement is not affected by the length of the signal
interconnection cable when remote mounting of the Signal Converter is required, as long as the
Bailey-Fischer & Porter supplied interconnection cable is utilized. The nominal maximum transmis-
sion distance for rated conductivities is limited to 80 meters (250 feet), however longer distances can
be accommodated (contact factory for details of using a special, driven-shield cable).
Primaries with integrally mounted Signal Converters use an encapsulated buffer preamplifier for each
electrode, it is not possible to effectively measure the AC resistance of the electrodes to determine
the process fluid conductivity. The conductivity may be checked from actual process fluid sample
measurements or from other known data. Bailey-Fischer & Porter Applications Engineers are quali-
fied to determine the conductivities of special liquids, please contact the factory if assistance is
required.
1-4
Q = 4 Q
2
πD
A
4 Q
2
α πD
2
• E
s
4 B
s
E
r
INTRODUCTION