Design and implementation of verification device for dissolved oxygen tester

Abstract

Due to the low validation efficiency and large human error of the dissolved oxygen tester, a new calibration device was developed for the dissolved oxygen validation, which has the functions of accurately controlling the experimental temperature, accurately measuring the atmospheric pressure, and automatically calculating the standard value of dissolved oxygen. The temperature and concentration homogeneity of the liquid to be probed are two important parameters that affect the validation results. In this paper, we use the Fluent simulation software to model and simulate the uniform distribution of temperature and dissolved oxygen concentration in a validation tank. When the temperature of the verification device is set at 10°C, 20°C and 30°C respectively, each 10 mm is selected as a measurement plane in the range of 10 mm to 80 mm of the detection depth, and five test points are selected on each measurement plane to carry out simulation tests. The experimental results show that the concentration of dissolved oxygen is less than 0.27% uniform within the same measurement plane and less than 0.39% uniform between different measurement planes. To verify the validation effectiveness of the proposed device, three dissolved oxygen testers from different manufacturers were selected for the validation work. The error of temperature indication value of the three instruments is not more than ±0.1 °C, the measurement repeatability is not more than 0.02 mg/L, and the error of dissolved oxygen concentration indication value is not more than ±0.08 mg/L, which all meet the requirements of verification regulations. The results show that the proposed device can be effectively applied for the validation of dissolved oxygen meters.