Development Of Water Quality Measuring System Using Spectrophotometry Based On LED Array

In the process of measuring water quality, different color reactants which are chosen according to the measured parameters have different spectral absorption characteristics. At the characteristic absorption wavelength, the absorption of light energy depends on the content of the measured ingredients. The water quality measuring system based on LED array is designed according to these features. This measuring system adopts specific LED as the monochromatic light source. The SCM is the core of this instrument. With the external circuit such as A/D, this instrument can achieve the conversion, processing, operations of the signal and control the instrument to display and print. This instrument had many characteristics such as simple optical light path, low-power, small volume and easy to carry.In this article, I analyze the working principle of the water quality measuring instrument which is based on the Lambert-Beer's law and focus on the LED array based portable water quality analysis instrument. The orbicular water quality measuring instrument is designed according to the linear relationship between absorbance and concentration. What I have achieved is as follows,â‘ LED array-based emitting light transmitted assembly and transmission light receive assembly;â‘¡the conversion of the optical and electronical signal using photoelectric triode, the completion of multi-channel signal choice using ADG608 and the completion of A/D using AD7896;â‘¢the completion of the SCM hardware and software systems, including keyboard controlling, printing, display on LCD, processing and calculating the data obtained by A/D conversion, amending the standard curve according to the needs of the user, displaying the measuring results on LCD and printing;â‘£experimenting on the solution with standard concentration and fitting the experimental data using linear regression analysis; writing the standard working curve into the measuring system by operating the keyboard.The portable water quality measuring instrument based on LED array provides a new testing method which has simple structure and can achieve real-time detection.