What is the principle of magnetic scale?

Principle: Magnetic scale is mainly composed of two parts, magnetic scale and read head. The magnetic read head and the magnetic scale are mounted non-contact to read, the mounting distance is 0.1-2mm, the NS-SN-NS poles on the magnetic scale generate magnetic field with different directions, the magnetic read head senses the change of magnetic field in the process of moving along the magnetic scale, and converts the change of magnetic field into analogue signal or digital signal output.