A basic magnetic flowmeter, also known as a magnetic flow sensor or magmeter, is a type of flowmeter used to measure the flow rate of conductive fluids (liquids or slurries) in pipes. It operates based on the principle of electromagnetic induction, taking advantage of Faraday's law of electromagnetic induction.
Here's how a basic magnetic flowmeter works:
Fluid Flow: The fluid (liquid or slurry) that needs to be measured flows through a pipe or conduit. It's important that the fluid is conductive, meaning it contains ions that can carry an electric charge.
Electromagnetic Coils: The magnetic flowmeter has two sets of electromagnetic coils. One coil, called the "excitation coil" or "drive coil," is responsible for generating a magnetic field. This coil is wound around the pipe and generates a magnetic field perpendicular to the flow direction.
Electrodes: The second coil, called the "detection coil" or "pickup coil," consists of two electrodes placed on opposite sides of the pipe. These electrodes are used to measure the voltage generated by the moving conductive fluid as it passes through the magnetic field.
Magnetic Field and Induction: When the conductive fluid flows through the pipe, it cuts across the lines of the magnetic field generated by the excitation coil. According to Faraday's law of electromagnetic induction, the movement of the conductive fluid through the magnetic field induces a voltage across the electrodes in the detection coil.
Measured Voltage: The induced voltage is directly proportional to the flow velocity of the conductive fluid. As the fluid flow rate changes, the induced voltage across the electrodes changes accordingly.
Flow Calculation: The induced voltage is measured and converted into a flow rate using the flowmeter's internal electronics. The relationship between the induced voltage and the flow rate is typically determined during the calibration of the flowmeter.
It's important to note that this type of flowmeter is most accurate when measuring conductive fluids because the induction process relies on the presence of charged particles in the fluid. Additionally, the pipe must be completely filled with the fluid, as any air gaps or pockets could disrupt the accuracy of the measurement.
Magnetic flowmeters have advantages such as being relatively low maintenance since they don't have moving parts in contact with the fluid, and they can be used for a wide range of applications, including water treatment, chemical processing, and wastewater management. However, they may not be suitable for non-conductive fluids or fluids with low conductivity.