Research On The Method Of Water Colority Automatic Detection Based On Fibre-optic Sensor

Water environmental monitoring is an important fundamental workto exploit and protect water resource rationally. Generally speaking, all kindsof pollution will lead to the change of water appearance, such as colour andtransparency. Thus, water pollution control can be started by the control ofwater colority, and make the water colority as monitoring index. Currently,there are two national standard methods visual colorimetry and dilutionmultiple method to determine the water colority. Both methods need sense todetermine by eyes, have large man-made factors, cumbersome to operate, andit is not suit for on-site automatic detection and real-time monitoring.According to the limitations of the determination methods of watercolority, colorimetry theory was applied, related colorimetry parameters ofPlatinum-Cobalt standard solutions were measured by spectrophotometer, therelationship between colorimetry parameters and colority of national standardmethods was established. Through the relationship, the water colority can bedetermined. After analyzing and comparing several programs of coloritydetermination, the LAB color-difference colority determination program waschosen. The distinguished minimum threshold value of color-difference is notthe same owing to different hue, hue was divided in six intervals by dominatewavelength, the LAB color-difference value of different hue was measured byexperiments, and the relationship between LAB color-difference value andmultiple value was established. In the yellow hue interval, the relationshipbetween colority value and multiple value was established, the meaning ofcolority value was extended from single yellow hue to any hue, twomeasurement results of national standard colority determination methodswere integrated together. The measurement results show that this method notonly guarantee the determination results are conforming to the resultsdeterminated by national standard method, but also is more objective, morereliable, more sensitive, more accurate, laying the foundation for automaticdetection and real-time monitoring of water colority. On the basis of proposed theoretical model and experiment methods forwater colority determination, considering the superiority of fibre-optic sensor,an automatic detection equipment of water colority was designed and setbased on Light-transmission fibre-optic sensor. This equipment contains lightsource, fibre, fibre-optic sensor, fiber optic spectrometer and portablecomputer. Through researching exploring on the structure of the intrinsicevanescent wave fiber-optic sensor probe, a higher sensitivity intrinsicevanescent wave fiber-optic sensor probe was designed. In view of the needof practical application, self-made software which is user-friendly, easy tooperate, suit for automatic detection was developed. After the fibre-opticsensor system has taken picketage tests, it can be used to detect watercolority automatically, report the water colority index and relatedcolorimetry parameters in real time. If the colority of water sample is out ofrange, the system will alarm right now to reduce the risk of being polluted,having a practical significance for the monitoring and protection of waterresource.