# Which type of voltage goes out to the magnetic flow meter AC or DC ?

A magnetic flow meter typically operates with AC (alternating current) excitation. AC excitation is commonly used because it induces a varying magnetic field in the flow meter’s measuring tube, which interacts with the conductive fluid passing through. This interaction generates an electromotive force (EMF) or voltage across the electrodes placed in the flow meter. The frequency of the AC excitation is typically chosen based on the characteristics of the fluid being measured and the desired accuracy of the flow meter.

The output of a magnetic flow meter is typically an analog signal or a digital signal representing the flow rate of the conductive fluid passing through the meter. This output signal is proportional to the velocity of the fluid and is often converted into engineering units such as liters per minute or cubic meters per hour, depending on the application and calibration of the flow meter.

DC (direct current) excitation is not permitted in electromagnetic flow meters primarily because it does not induce a varying magnetic field in the measuring tube. Electromagnetic flow meters rely on Faraday’s law of electromagnetic induction, which requires a changing magnetic field to induce a voltage in the conductive fluid. DC excitation would result in a steady magnetic field, which does not produce the necessary variation to generate a measurable voltage across the electrodes. Therefore, AC excitation is essential for the proper operation of electromagnetic flow meters to accurately measure flow rates based on induced voltages proportional to fluid velocity.

The voltage induced in a magnetic flow meter is proportional to the average flow velocity of the conductive fluid passing through the metering tube. As the conductive fluid moves through the magnetic field generated by the flow meter’s coils, it generates a voltage across the electrodes placed within the flow meter. This induced voltage is directly proportional to the average velocity of the fluid, allowing the flow meter to measure and quantify the flow rate based on this relationship. The proportionality between induced voltage and flow velocity forms the basis for the accurate measurement capabilities of electromagnetic flow meters across various fluid flow conditions.

A magnetic flow meter operates based on the principle of electromagnetic induction. It consists of a non-conductive measuring tube through which the conductive fluid flows. Inside the flow meter, coils are placed to generate a magnetic field perpendicular to the direction of fluid flow. When an AC current flows through these coils, it creates a varying magnetic field in the measuring tube. As the conductive fluid moves through this magnetic field, it generates a voltage according to Faraday’s law of electromagnetic induction. Electrodes positioned on the walls of the measuring tube detect this induced voltage, which is proportional to the average flow velocity of the fluid. By measuring this induced voltage and applying appropriate calibration factors, the magnetic flow meter accurately calculates and outputs the flow rate of the conductive fluid. This method allows for precise measurement of flow rates in various industrial applications, including water treatment, chemical processing, and wastewater management.