A CMOS Sulfur Dioxide Concentration to Time Period Converter for Measuring Sulfur Dioxide Concentration in Food Applications

A CMOS sulfur dioxide concentration to time period converter is newly proposed for measuring sulfur dioxide concentration in food applications. The proposed converter can transform sulfur dioxide concentration in solution into time period linearly. Through the time period, sulfur dioxide concentration in solution could be easily and quickly obtained. In order to be suitably used in different kinds of sulfur dioxide concentrations in solution, a converter with the range of low resistance was designed, which was 100 $\Omega$ to 100 k$\Omega$. The inputted range of sulfur dioxide concentration in solution was 200 to 1600 ppm, the corresponding outputted range of the proposed converter with sulfur dioxide sensor was 471.65 $\mu \mathrm{s}$ to 1.166 ms. The proposed chip could be used for sensing sulfur dioxide concentration in food applications.