Bamomatic
Those flow meters are calibrated on a test bench with a precision better than ± 5 pulses /1000. Tests are carrying out at room temperature with water.
In an electromagnetic flow meter, the fluid section is in a magnetic field originated by toroidal spools. Electrodes, fitted at 90° from the fluid movement and in contact with the conductive liquid measure the generated potential. This potential is proportional to the speed flow (Faraday law) and to the flow rate if the pipe section is constant.