The main performance requirements of encoder are: high precision, high sensitivity, reliable work, good stability, strong anti-interference ability, good dynamic characteristics, simple structure and low cost. The main items to be checked include: appearance; starting moment of main shaft; allowable speed; allowable axle load (axial and radial); inertia moment; vibration resistance; shock resistance; high temperature resistance; anti-interference ability; power voltage adaptability; current consumption; output signal amplitude and phase relationship; phase difference change (phase degree); output pulse accuracy (decomposition); duty cycle; rise and fall time; response frequency; Average life; length of extension cable, etc.