A design work for λ analyzer is carried out

which uses STM32f407 as core processor and universal exhaust gas oxygen（ UEGO） sensor as sensitive component

measuring theory of UEGO sensor is described

and theoretical formular of limiting current and air-fuel ratio is deduced. Hardware circuits such as signal detecting and processing circuit working temperature control of sensor

and LCD are designed

hardware circuit of λ analyzer is designed. Combined deduced formula with hardware circuit

software driving program is compiled. In order to optimize the performance of the temperature control

and air to fuel ratio more accurate

PID control algorithm is introduced into the process of sensor operating temperature control.