Magnetic flowmeters are
among the most widely used types of flowmeters for measuring the flow of
water and other liquids. They
have been around for more than fifty years.
The Tobinmeter Company first introduced magnetic flowmeters for
commercial use in Holland in 1952. Foxboro
introduced them to the United States in 1954.
Since this time, more than 35 suppliers worldwide have come to offer
magnetic flowmeters for sale.
about New Technology Flowmeters:
flowmeters generate more revenues worldwide than any other type of
flowmeter. Revenues from magnetic flowmeters exceed revenues from all other
flowmeter types, including Coriolis, positive displacement, turbine, and
differential pressure (DP) types. The
story is different in terms of units, however.
More positive displacement, turbine, DP, and variable area
flowmeters are sold annually than are magnetic flowmeters.
Despite this, the higher average selling price of magnetic
flowmeters enables them to generate more revenues annually than these other
types of meters.
flowmeters are most widely used in the water & wastewater and chemical
industries. About half the
revenues generated by magnetic flowmeters are due to sales into these
industries. These meters are
also widely used in the food & beverage and pharmaceutical industries,
which often require flowmeters to conform to sanitary requirements.
Flowmeter suppliers meet these requirements in part by placing
sanitary liners inside the meters that make them suited for sanitary
flowmeters use Faraday’s Law of Electromagnetic Induction.
According to this principle, when a conductive medium passes through
a magnetic field, a voltage is generated. This
voltage is directly proportional to the velocity of the conductive medium,
the density of the magnetic field, and the length of the conductor.
In Faraday’s Law, these three values are multiplied together,
along with a constant, to yield the magnitude of the voltage.
flowmeters use wire coils mounted within or outside of the meter body.
A current is then applied to these coils, generating a magnetic
field. As the conductive
liquid passes through the body of the meter, a voltage is generated and
detected by electrodes, which are mounted on either side of the meter body.
The flowmeter uses this value to compute the flowrate.
flowmeters are used to measure the flow of conductive liquids and slurries,
including paper pulp slurries and black liquor.
Their main limitation is that they cannot measure hydrocarbons
(which are nonconductive), and hence are not widely used in the oil &
gas and refining industries. Magmeters,
as they are often called, are highly accurate and do not create pressure
drop. Their initial purchase
cost is in the medium range, and comparable to the cost of vortex
flowmeters typically cost more than positive displacement and turbine
flowmeters, but they cost significantly less than Coriolis and ultrasonic
further information, including detailed market reports, please see www.FlowMags.com.