Working principle of displacement sensor based on magnetostrictive effect of Fe-Ni alloy material is introduced

by applying current pulse signal to magnetic material

vertical and annular magnetic field

which can be coupled to the permanent magnetic field

are generated

respectively. In this way

magnetoelastic wave propagating along the magnetostrictive wire is produced. Due to the exciting current and reflection elastic wave

two pulse signals are created in the detecting coil. The time interval of the two pulse signals is directly proportional to displacement of permanent magnet. Generation of pulse excitation current and sensing signal processing circuits of detecting coil are designed

two pulse signals which reflect time difference are converted to pulse width modulation（ PWM） signal. Therefore

two kinds of output reflect displacement are used to one is the time differece and another is the analog voltage. By experiment of Fe-Ni alloy at range of 84 cm

results show linearity of displacement are 0. 165 % FS and 0. 175 % FS

when the excitation signal pulse width is 10 μs

and its the power amplifier value is 10. 3 V and turns number of detecting coil is 600 turns.