The permanganate index is a common indicator reflecting the pollution degree of organic and inorganic oxidizable substances in water. It is defined as: under certain conditions, potassium permanganate is used to oxidize certain organic and inorganic reducing substances in water samples, which is consumed by consumption. The amount of potassium permanganate is calculated as the equivalent amount of oxygen.

According to the difference of chloride ion content, permanganate index determination is divided into acid method and alkaline method. When the chloride ion concentration exceeds 300mg/L , the alkaline method is used, and vice versa.

When measuring different water samples, you will encounter water samples with a variety of complex components, such as turbid water samples, water samples with suspended solids, and water samples with brown precipitates after the digestion is completed and sodium oxalate is added to the reaction (chloride ion content) High), will have an impact on the automatic endpoint color judgment.

At present, several commonly used automatic instrument endpoint determination methods on the market are: RGB color sensor, but when the RGB color sensor determines the lighter color solution, the value fluctuation is not obvious, and the signal can not be given to determine the endpoint, liquid reflection and different sample cups It has a great influence on the fluctuation of the value, the measured value is unstable, and the turbid water sample is not easy to identify; in addition, the end point is determined by the method of spectroscopy. The same spectroscopy method is not easy to identify the lighter color, and the reflected light of different sample cups will also have The signal response is very slow. In addition, it is impossible to determine the turbid water sample with suspended solids, which affects the wavelength absorption of a specific color. Through trials of these sensors, it was found that none of the sensors could solve the light pink color determination at the end of the permanganate index. First, the color recognition effect was not good, the second was too many interference factors, and the third was that the communication speed was too slow.

Based on the above-mentioned shortcomings, the color judgment of ST108 series high-precision automatic permanganate index analyzer developed by our company adopts the international leading imported full-color gamut visual analog sensor, which is not affected by turbidity, sample cup, background, light and other factors. , It adopts human visual simulation, has powerful image analysis and processing functions, and has fast response speed. It can individually process the end color of complex water samples (see appendix 1 ), and meet the color judgment of different water samples by switching programs.