The Research Of Technology On Scattering-Light Turbidimeter And Signal Processing

Along with the develop of society, the effect of water is strengthen in people's live and industrial production day after day. Turbidity is regard as a key technical parameter in the water quality measurement. As a instrument measuring turbidity, turbidimeter is widely applied to these industries, such as, environmental protection department, hydrographic measurement, food industry, medicine, electronics, energy source and etc.In company with the dramatic development of electronic technique, the turbidimeter is evolved from hand-oriented instrument to integrated, multifunctional, intellectualized instrument. As the research of turbidimeter begins too late in our country, comparing with the import turbidimeters, the domestic products is under-developed in performance and stability, but the import turbidimeter is complex to operate and much more expensive, so it can not used popularly. Consequently, the reseach and design of turbidimeter is very important.Introduce the principle of light absorption and scattering, which is the theoretical basis of turbidimeter works and understand the basis of photology further. According to the international standard ISO7027,we can know that the measurement of turbidity mainly use the optical turbidimeter measurement,it contains the scattering-light method and transmitted-light method. The scattering-light method has application in measurement for low turbidity water and also can used in high turbidity water.On the other hand,the transmitted-light method is more suitable for high turbidity measurement. After analyzed the advantages and disadvantages of nephelometric methods, according to the topic, select the scattering-light method,and put the light detector at 90°to decrease the effect of stray light.Choose the 890nm infrared LED as the light source after compared the capabilities of incandescent lamp/tungstic lamp and LED/LD and also think about the selective absorbability of water; it has strong points such as constant light intensity,long life, narrow light spectrum,etc, and use the infrared light with 890nm wavelength to decrease the influence of optical-absorption matters.Choose the photosensitive diode which suitable to the LED which we choosed after compare the capabilities of light sensitive resistor, photocell, photosensitive diode and phototriode. Both of these make up the photoelectric system of turbidimeter.Use the enhanced, low power 8-bit microcontroller ATmega16 produced by ATMEL Company to design the hardware system of turbidimeter.We choose secondlevel signal mu-circuit to measure the tubidity in practical situation,use the instrument amplifier AD623 to make up the first amplifying circuit,as it can enhance the measure sensitivity. To eliminate the backgroud light and heterogeneous light, we design a simple and multipurpose water chamber.At last, we have done turbidimeter lab experiments. We compare the capabilities of turbidimeter in the matter of process the air bubble,water colour and organics disturbances. The result of tests proves that the turbidimeter we design can measure the turbidity of water.