Magmeters, also known as electromagnetic flow meters, measure the voltage generated when conductive liquids pass through a magnetic field. According to Faraday's Law, the voltage induced across any conductor as it moves at right angles through a magnetic field is proportional to the velocity of that conductor. In the case of magmeters, the liquid serves as the conductor, and the magnetic field is generated by energized coils outside the flow tube. Electrodes detect the voltage, which is directly proportional to the flow rate.
Magmeters are capable of measuring corrosive liquids and slurries, and they can measure flow in both directions with equal accuracy. To operate, a conducting fluid and a non-conducting pipe liner are required. However, they are generally not suitable for use with hydrocarbons, distilled water, and many non-aqueous solutions. They are an ideal choice for applications where low pressure drop and low maintenance are desired.
When selecting a flow meter, it is essential to have a clear understanding of the requirements of the particular application. It is important to evaluate the nature of the process fluid and the overall installation. Some key questions to consider include:
- What type of fluid is being measured (air, water, etc.)?
- Do you require rate measurement and/or totalization from the flow meter?
- If the liquid is not water, what is its viscosity?
- Is the fluid clean?
- Do you require a local display on the flow meter, or do you need an electronic signal output?
- What is the minimum and maximum flow rate for the flow meter?
- What is the minimum and maximum process pressure?
- What is the minimum and maximum process temperature?
- Is the fluid chemically compatible with the flow meter wetted parts?
- If this is a process application, what is the size of the pipe?
