A magnetic flow meter, also known as a magmeter, operates based on the principle of electromagnetic induction to measure the flow rate of conductive fluids (such as water or liquid metals). Here's a general overview of the principle of operation:
Magnetic Field Creation: The magmeter consists of a flow tube made of non-magnetic material, typically with a circular cross-section. Coils are mounted on the outside of the flow tube, which generate a magnetic field when an electric current passes through them. These coils are referred to as the excitation coils.
Conductive Fluid Flow: The fluid to be measured flows through the flow tube. It must be conductive to allow for the measurement of flow using electromagnetic principles.
Faraday's Law of Electromagnetic Induction: According to Faraday's law, when a conductor (the conductive fluid) moves through a magnetic field, a voltage is induced across the conductor perpendicular to both the magnetic field and the direction of fluid flow. In the case of a magmeter, the conductive fluid acts as the moving conductor.
Electrodes and Voltage Measurement: Inside the flow tube, there are two electrodes mounted diametrically opposite to each other, usually flush with the tube wall. These electrodes are in contact with the conductive fluid. When the fluid flows, it generates a voltage across the electrodes due to the magnetic field passing through it.
Measurement of Induced Voltage: The voltage induced across the electrodes is proportional to the velocity of the conductive fluid, which is directly related to the flow rate. The magmeter measures this induced voltage.
Flow Rate Calculation: The magmeter includes a transmitter unit that receives the induced voltage signal from the electrodes. It amplifies, conditions, and processes the signal to calculate the flow rate based on the relationship between the induced voltage and the flow velocity. The transmitter may also compensate for various factors like fluid conductivity, temperature, and other parameters to improve the accuracy of the flow measurement.
It's worth noting that the magnetic flow meter requires a conductive fluid to work properly since the measurement is based on electromagnetic induction. Additionally, the magmeter design may incorporate additional features like a lining material to protect against corrosion or turbulence-reducing elements in the flow tube to improve measurement accuracy.
Overall, the magnetic flow meter utilizes the principles of electromagnetic induction to measure the flow rate of conductive fluids by detecting the induced voltage across electrodes in the presence of a magnetic field.