Electromagnetic flow meter use Faraday's low of electromagnetic induction. In this meter, magnetic field is generated by pair of coils.

Let us understand working of electromagnetic flow meter. When conductive liquid passes through the EM field, electric voltage is induced in the liquid. This voltage is directly proportional to its velocity. Moreover the induced voltage is perpendicular to both liquid flow direction and EM field diection as per Fleming's right hand rule.

The induced voltage is not affected by physical properties of liquid such as temperature, viscosity, pressure, density and conductivity. For reliable measurement, pipe should be full of liquid. Moreover electrical conductivity of liquid should be atleast 5 micro siemens per cm.

Typically there are two types of electromagnetic flow meters available in the market.

Flange type electromagnetic flow meter : This flow meter is installed in straight pipe line by doing necessary plumbing work. A relatively short length of straight pipe is needed to install this meter. This flow meter is available in two types viz. integral and remote type. In integral type flow meter, converter is integrally installed with flow meter body. In remote type, measuring sensor unit is installed with water pipe and converter is placed at another station and connected using wires.

Insertion type electromagnetic flow meter : This flow meter is suitable for large diameter pipes. They are installed where water supply can not be cut off even for smaller duration. They do not require much plumbing work. In this flow meter, sensor can be installed by inserting the meter between two flanges of pipe without removing the measuring pipe.

Advantages of Electromagnetic Flow Meter

➨It does not have any moving parts and hence they are minimally affected by flow of disturbances related to viscosity or density.
➨The EM flow meter does not obstruct flow. Hence it can be used for clean, sanitary, dirty, corrosive and abrasive liquids.
➨EM flow meter measurement does not affect due to state of flow such as laminar or turbulent.
➨EM flow meter is used as volume flow measuring instrument. In addition, it can be used to measure temperature of medium, its viscosity, density and electrical conductivity.
➨Electromagnetic flow meter offers better performance and reliability.

Disadvantages of Electromagnetic Flow Meter

➨It requires power supply for its operation.
➨Electronic components used in EM flow meter are more vulnerable to damage.
➨The repairing of EM flow meter requires specialized equipments. Moreover it requires skilled technicians. This increases cost to maintain the meter.