The operating principle and architecture of both hardware and software of the single chip computer based intelligent instrument for this purpose are presented in this paper.

Making use of rotary encoder attains the purpose of measuring rotative Angle of wiper through single chip computer 8051 to count the pulse of rotary encoder generating, which is drove by wipers axle.

The purpose is making use of single chip micro-computer to control four processes of mutual welding of reinforcing steel bar, which makes automatic mutual welding realize really intelligent control.