Magnetic displacement ruler

A magnetic displacement measurement device, comprising a ruler body and a vernier which can move with respect to the ruler body, wherein a magnetic main ruler is fixed on the ruler body, and a secondary ruler is fixed on the vernier;

• the secondary ruler comprises a magnetic sensor and a measurement circuit thereon;
• said measurement circuit outputs the signal of movement distance to a signal output device;
• being characterized in that:
• said magnetic main ruler is of grid type, wherein grids are arranged at a constant interval along a movement direction with a grid pitch of λ;
• said magnetic sensor is composed of giant magnetoresistances which are opposite to the magnetic main ruler and arranged along the movement direction;
• and
• said measurement circuit comprises at least two measurement bridges which are composed of giant magnetoresistances and are electrically connected with an AC power supply, such that the measurement bridges receive AC power as input.