quick overview :

Magnetometers are measurement instruments to measure the magnetization of a magnetic field and to measure the strength. It is mainly used for the measurement of the Earth's magnetic field. Carl Friedrich Gauss in 1833 invented this device first. It is also useful to detect submarines in military.  It sometimes works as magnetometer and also used for mobile phones and tablet computers. Teslameter is a magnetometer which is used for determination of magnetic field intensity H and magnetic induction B. Teslameter is based on the principle of induction. For any change in the magnetic flux an electromotive force is produced in the coil.