The electric actuators are mainly composed of two parts of servo amplifier and actuator, the electric actuator is the execution unit in electric unit combination instrument, is the position servo mechanism driven by servo motor. The electric actuator accepts  0 ~ 10 ma, or 4 ~ 20 ma DC signal, from the regulator, and linearly transform into 0 ~ 90 ° angle or linear position displacement, to operate the regulating mechanism of damper, baffle and valve in order to realize automatic adjustment.