Institute of Electronic Engineering;
Chung Yuan Christian University;
Chung-Li;
Taiwan 320;
China;
Graduate School of Electronic Engineering;
National Yunlin University of Science and Technology;
Douliou;
Taiwan 640;
China;
Department of Electrical Engineering;
National Chi Nan University;
Nantou;
Taiwan 545;
China;
tin oxide sensing membrane; sol-gel method; spin-coating technology; pH sensing electrode;