Study On A New Economic Smart Turbiditor

Turbidity, an important parameter of water quality, is used to indicate the degree of clarity or turbidity. Turbidity monitoring is gradually be taken seriously because of the attention on health and environmental protection. Turbiditor, an instrument to measure the turbidity, is widely used in food, environmental monitoring, medical and other fields.Turbiditor appears the trend of intelligent, diversification and multi-function as a result of the development of computer and the application of new materials and new technics . Although turbiditor in China has grown by leaps and bounds since the 1980s, yet large gap still exists compared with famous brands, especially in reliability and stability .The on-line instrument market is dominated by foreign brands, but the high price is an obstacle to wide application. So, research of intelligent turbiditor is of great significance.The paper first introduce the measure principle including transmitted-light method, scattered-light method, surface scattered-light method and ratio method. In the medium and low turbidity, ratio method shows the best overall performance. Considering the range of the products, choose the ratio method.The economy and the practicality are fully concerned in the design of measurements pool. Funnel allows consumer use their own standards in online calibration, and the inlet is installed in the bottom of the pool to emit bubbles, and last, symmetrical ring structure of the pool is help emitting the effect of light absorption. The pool makes consumer no longer need solid standard in calibration, and emit bubbles easily.Sensor design is include light source, luminant and detector. First, luminescent spectrum is setted in infrared light district to hurdle color interference. Secondly, choose IR LED as luminant because of its characters such as low-power, long-lived, narrow-spectrum light, easy to adjust the light intensity. The last, choose photodiode with linear output and fast response as detector.The bright spot of the transmitter is the sample circuit . The one is , use ICL7650 with high-gain, high CMRR, small disorder, low drift and the merits of the operational amplifier as pre-amplifier edging out the traditional two-stage amplifier. The other, use∑-△A/D converter with high-speed, high-precision to take out S/H and multiplex switch. Thus measures reduce the hardware and optimize the structure.Intelligent Turbiditor use ATMEL's 89S52 as MCU. Many works such as switching the luminant state, inputting the signal of scattered and transmitted alternately , taking charge of digital filter, calculating and displaying turbidity, all of these are beared by 89S52.The output in the range is proved a good linearity through regression analysis of experimental data and related analysis .At last , paper summarize the results in the sensor circuit, the transmitter circuit, structural design of measurements pool. And, raise the works in the late development such as automatically cleaning, improving function, reducing the volume.