A Robust Sensor for Inline pH Measurements

Conventionally, a pH sensor having a glass bulb and a liquid-based reference electrode is used for accurate, real-time pH measurement. However, glass bulb-based pH sensors suffer wear and tear in harsh operating conditions and yield erroneous readings in strong alkaline and acidic media. This necessitates the development of a robust pH sensor that renders stable performance in harsh operating conditions. This paper reports the fabrication and characterization of an all-solid-electrode pH sensor with excellent linearity in the pH range of 4 to 9 with a sub-Nernstian slope of -43.18 mV/pH. The fabrication process of the sensor is explained in detail, and the performance of the sensor is validated with extensive characterization. Furthermore, the efficacy of the sensor in practical applications is established by measuring the pH of idli batter during its fermentation process. The proposed sensor is also used to measure the pH of soil solutions, wherein the pH of soil samples showed an error of less than ±0.15 pH when compared with a laboratory pH meter.