Understanding How Magnetic Flowmeters Work and the Difference between AC and DC Excitation

The electromagnetic flowmeter, commonly known as the "magmeter", gets its name from the magnetic field generated within the float tube that produces a signal proportional to flow. This principle employs Faraday's Law of Electromagnetic Induction. Magnetic flowmeters are built so the direction of the magnetic field is perpendicular to the flow and the line between the electrodes is also perpendicular to the flow. As a conductive liquid flows through the flowtube, an electro-motive force is generated. The electrodes detect the electro-motive force. The electro-motive force is proportional to the flow velocity, flux density, and the meter inner diameter. The flux density of the magnetic field and the meters inner diameter are constant values, therefore the magnetic flow meter can calculate the flow velocity and volumetric flow from the electro-motive force.

The basic components of the magnetic flow meter body are:

  1. A lined flowtube (typically Teflon)
  2. Excitation coils
  3. Two electrodes mounted opposite of each other within the flowtube.

Current is applied to the coils in the magmeter to generate a magnetic field within the flow tube. As a conductive fluid flows through the meter, an electro-motive force is generated. This force is detected by the electrodes and the resulting value is converted to flowrate.

For more information on magnetic flowmeters, contact Miller Energy, Inc. by calling 800-631-5454 or by visiting https://millerenergy.com.