Optical Absorption COD Sensor for Real-Time, Low-Power-Consumption, Long-Term Monitoring

Compared with the chemical method, absorption spectroscopy can be used to measure chemical oxygen demand (COD) in real-time monitoring without pollution. However, there is a significant challenge in performing low-power-consumption, long-term, fast, and accurate COD monitoring in open waters. In this study, a COD sensor with low-power-consumption, long-term, real-time monitoring capabilities is proposed. The sensitivity is 0.0083 (mg/L) $^{-1}$ , the resolution is 0.08 mg/L, and the power consumption of the instrument in one cycle is approximately 0.0505 mAh. To improve the measurement accuracy of the COD sensor, the influence of temperature and natural light on measurements was studied, and a compensation method is proposed. Experimental results in the Back Lake indicate that measurement error is less than 1.6 mg/L after compensation of temperature and natural light compared with 5 mg/L before compensation.