Design of Turbidity Remote Monitoring System Based on FX-11A Optical Fiber Sensor

Turbidity is an important indicator in the monitoring area of industry, production and living. Facing the trend of remote monitoring and preset warning in the development of monitoring system, this paper, based on the FX-11A optical fiber sensor and STM32F407 Microcontroller, puts forward a design of remote monitoring system for turbidity, which can realize preset warning function. According to Lambert-Beer Law, an experimental apparatus is designed, and the exponential relationship between the ratio of the reference voltage (Vm) and the measured voltage (V) and the turbidity is found out. Based on the relationship and experimental setup, the design performs two sets of experiments by using two kinds of determinands. In the first experiment, the mixture of soil and water are used to detect the change of turbidity. The results show that the system can distinguish the demarcation between the soil and water layers in real time by the optical fiber sensor and the first channel of Analog-to-Digital Converter (ADC1) in STM32F407 Microcontroller. In the second experiment, the Formazin standard solution is adopted to compound a series of solution with concentration gradient solution for accurate measurement. After measuring, MATLAB is used to fit data. The results conform to the Lambert-Beer Law and an accurate measurement in some turbidity range is obtained. In conclusion, the correlation coefficients are obtained. R-square is as high as 0.9955 and the system is capable of measuring within 3.5% of error in the range 400 to 1500 Nephelometric Turbidity Unit (NTU). Combining the former system that is designed, and a remote monitoring system with Ethernet transmission function based on STM32F407 Microcontroller, functions of remote monitoring and preset warning in line with the development trend of monitoring system can be achieved.