Measuring Flow with an Electromagnetic Flow Meter
Electromagnetic flow meters actually measure the
velocity (speed) of fluids in a pipe. Flow is then
automatically calculated in the controller by
multiplying the velocity by the cross sectional area
of the pipe. FLOW (Q) = AREA x VELOCITY. Since the
cross sectional area of the pipe can be calculated
from the pipe diameter we need only know the
velocity of the fluid in order to calculate the
flow.
Measuring Flow with an Electromagnetic Flow Meter
FLOWMETER OPERATION
The magnetic flowmeter consists of a
non-magnetic pipe lined with an insulating material.
A pair of electromagnetic coils is situated and a
pair of electrodes penetrates the pipe and its
lining (as shown below). Magmeters can detect the
flow of conductive fluids only (greater than .05
microsiemens). The operation of magnetic flowmeters
is based on Faraday's law of electromagnetic
induction.
As a conductive fluid flows through the magnetic
field generated by the coils, a voltage (E) is
developed across the electrodes, as predicted by
Faraday's law. The voltage will be proportional to
the velocity (V) of the liquid. Because the magnetic
field density and the pipe diameter are fixed
values, they are converted into a calibration factor
(K) which is labeled on each sensor.
E = K x V. The magmeter's K factor is
determined by a traceable wet calibration of each
flow sensor during manufacture. This K value is
valid for any conductive liquid and is linear over
the entire flowmeter range. Magmeters can measure
flow in both directions, as reversing direction will
change the polarity but not the magnitude of the
signal.
FLOMOTION electromagnetic flow meters generally
consist of two main sections, the meter itself and a
controller unit which interprets the signal received
from the sensor and displays the flow on a readout.
Most models have the option of having the controller
unit separated from the meter itself via a pair of
cables. This allows easy access to the controller
for wiring control and alarm signals and for viewing
the display and adjusting program parameters.
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For a flow meter to give accurate readings, it must
be properly installed. Electromagnetic flowmeters
must have a full pipe in order to read accurately.
This is best accomplished by locating the flow meter
in the pipe at a point that will always be full. It
is also important to situate the flow meter in a
straight length of pipe.
SENSOR LOCATION
A rule of thumb is that the meter be located no less than 10 pipe diameters upstream and 5 diameters downstream of a bend or change in the pipe size.
Additionally, the flow meter should usually be placed ahead of, not after, a valve. Valves will distort a flow
pattern for as many as 25 pipe diameters downstream of the valve.
GROUNDING Magmeters require excellent grounding for best accuracy and special grounding techniques are sometimes needed. For example, when mounted a sensor in plastic or other non-conductive pipes a separate grounding ring may be required to provide a sufficient electrical connection to the liquid. These rings are easily placed on either side of the magmeter during installation.
MS501 Microflow Magmeter
Provides precise measurement in low-flow
applications
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Sizes: 1/8” – ¾”
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Flow Range: 0.034 – 50 GPM
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Pressure: 0 – 580 PSI
Molded polyurethane body brings Magmeter Technology to a very affordable price level
 MS501 Microflow Magmeter
Unique design utilizes hose clamps for quick, economical installations
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Sizes: 1”, 2”, & 3”
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Flow Range: 2.4 – 800 GPM
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Pressure: 0 – 90 PSI
Molded polyurethane body brings Magmeter Technology to a very affordable price level
MS1000 Wafer Magmeter
An economical design that combines accuracy and reliability of a full bore sensor
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Sizes: ½” – 16”
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Flow Range: 0.85 – 20,000 GPM
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Pressure: 0 – 580 PSI
Polypropylene, ebonite, & PTFE liners in a lightweight & easy to install flangeless style.
Wafer Style Electromagnetic Flowmeters
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 MS2500
Flanged Magmeter
Rugged full-flanged design
provides high accuracy with minimal straight run
pipe requirements
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Sizes: 1” – 48”
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Flow Range: 2.4 – 180,000 GPM
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Pressure: 0 – 5600 PSI
Polypropylene, ebonite, PTFE
liners. Standard sensors have submersible ratings
MS3770 Econ. Insert. Magmeter
Provides a low cost means of monitoring flows in larger diameter pipes
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Sizes: 3” – 80”
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Flow Range: 25 – 500,000 GPM
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Pressure: 0 – 850 PSI
Small diameter Stainless Steel sensor can be inserted through a 1” NPT tap
MS3770 Econ. Insert. Magmeter Provides a low cost means of monitoring flows in larger diameter pipes
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Sizes: 3” – 80”
- Flow Range: 25 – 500,000 GPM
- Pressure: 0 – 850 PSI
Small diameter Stainless Steel sensor can be inserted through a 1” NPT tap
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