Design Ideas of COD Analysis Instruments

The functions performed by the COD analyzer include COD detection, step voltage measurement of solution resistance, curve comparison, and cyclic voltammetry. The detection function of the low-concentration COD detector can be set with compensation and no compensation to detect in the solution. COD content.

In order to deal with the problem of low-concentration COD detection and reduce the influence of solution resistance on the test results, the IR compensation method is selected to improve the accuracy of potential control. The premise of iR compensation is that the solution resistance is known. The step voltage test function is used to complete the measurement of the solution resistance. After fitting the collected current data, the solution resistance is calculated.

The cyclic voltammetry test function provides the cyclic voltammetry scanning function. After collecting the measuring current generated under the constant-speed triangular wave scanning voltage, the cyclic voltammetry scanning curve of the working electrode is obtained. The curve comparison function can complete the intuitive comparison of multiple COD current data or many cyclic voltammetry curves to observe the changing rules of the curve.

Because the tester uses modular structure planning, both software and hardware planning have strong flexibility and scalability. Using the planned low-concentration COD detector, it can complete the measurement of the solution resistance and the measurement of the cyclic volt-ampere characteristic curve of the sensor.

After analyzing the COD test data of various glucose solutions with different concentrations, the results show that the resolution of the COD sensor is 2mg/L. According to the experimental data, this paper presents the low-concentration segmented broken line calibration method, which reduces the error of COD measurement in the low-concentration section.

With the development of industrialization, the problem of water pollution caused by industrial sewage has attracted more and more attention. Water quality monitoring is an important foundation for the management and maintenance of water resources. Chemical oxygen demand (COD), as a commonly used water quality monitoring indicator, is used to monitor the content of organic matter in water quality. Therefore, the detection of COD in water is of great significance to the identification of the degree of water pollution.

A low-concentration COD detector is planned, the hardware development environment is the National Instruments NI PXI series virtual instrument, and the software development environment is Lab VIEW. The sensor used by the detector is a self-developed COD sensor supplied by the School of Environment of our school, and its intention is to develop a low-concentration detector based on the COD sensor to meet the national 863 intention requirements.