A basic magnetic flowmeter, also known as a magnetic flow meter or magmeter, is a device used to measure the flow rate of conductive fluids (liquids) in pipes. It relies on the principles of electromagnetic induction to determine the flow velocity of the fluid passing through the pipe.
Here's how a basic magnetic flowmeter works:
Construction: The magnetic flowmeter consists of a pipe made of non-magnetic material, typically stainless steel, with an insulating liner on the inside. Inside the pipe, there are two electrodes positioned opposite each other along the diameter of the pipe. These electrodes are in contact with the fluid flowing through the pipe.
Magnetic Field: The flowmeter generates a magnetic field perpendicular to the direction of fluid flow. This magnetic field is created by passing a direct current (DC) through coils (also known as excitation coils) that surround the pipe.
Electromagnetic Induction: As the conductive fluid flows through the magnetic field, it acts as a conductor cutting through the magnetic lines of force. According to Faraday's law of electromagnetic induction, this movement induces a voltage across the electrodes perpendicular to both the magnetic field and the fluid flow direction.
Electrode Voltage Measurement: The voltage induced across the electrodes is proportional to the flow velocity of the fluid. The faster the fluid flows, the greater the voltage induced across the electrodes.
Flow Calculation: The flowmeter's electronics measure this induced voltage and convert it into a flow rate reading. The flow rate can be displayed on a local indicator, transmitted to a remote control system or data logger, or integrated into a process control system.
Compensation: To ensure accuracy, the flowmeter's electronics may take into account factors such as fluid conductivity, temperature, and pressure to compensate for variations that could affect the measurement.
It's important to note that magnetic flowmeters can only measure conductive fluids because the principle of electromagnetic induction requires the fluid to be a conductor. Additionally, these flowmeters are suitable for a wide range of applications, including water, wastewater, various chemicals, slurries, and other conductive liquids. They are preferred in situations where other types of flow meters, such as mechanical or turbine meters, may encounter issues due to factors like fluid viscosity, particulates, or corrosive nature of the fluid.
Overall, magnetic flowmeters offer reliable and accurate flow rate measurements, making them popular choices in industrial and commercial applications.