Study of Digital Dissolved Oxygen Analytical Sensor of ppb-Level

This paper introduces the structure and working principles of the digital dissolved oxygen (DO) analytical sensor of ppb-level. The new-style tri-electrode electrochemical sensor composed of working electrode (WE), auxiliary electrode (AE), and reference electrode (RE) is reported in this paper because of the limit reaction area of the WE, the long reaction time, and the little reaction cavity of the existing sensors. We prepare a nano-porous gold electrode with high specific surface area to increase the area ratio of the AE and the WE. It makes the new-style tri-electrode electrochemical sensor steadier, more reliable and stronger in anti-interference. This paper also introduces the design of the work system, which is composed of hardware circuit, signal sampling and processing circuit, and temperature compensation circuit. Compared with the DO analyzer made in the Swiss Orbisphere Company (tri-electrode structure), the precision of self-made DO analyzer reach to ppb-level and the full scale error is less than ±3%. In conclusion, the new-style tri-electrode electrochemical sensor can be widely used to measure DO in boiler feed water in thermal power plants.