Abstract: In detectins the vehicle classis system, how to amplify and isolate the vehicle-mounted signals in the complex electromagetic environment is the problem which the ergineers must pay great attention to and urgently needed to solve.To counter the demand of analog input of the Field sensor to scaling up, the multiple solutions are Compared and further discussed by the researchers. Based on the analysis of photo-coupler character, the design project is determined to use Nonlinear sensor photo-coupler of the consistent parameters and circuit feedback compensation. The scheme is simple and practical, cost-effechive, good linearity, strons anti-in terference capability,and has god engineering application value.

Key words: Nonlinear photo-coupler, Photoelectric isolation amplifier, Vehicle chassis , Measurement system