Develop Of Portable SOM Detector Based On LED Light Source

Soil organic matter is an important component of soil nutrient, which has a close relationship with soil fertility. The traditional measurement methods of soil organic matter always has a long measuring period or high cost. Therefore the development of a SOM fast measuring instrument has important significance. In this paper, we carried out the following work:(1)Described the basic properties and common measurement methods of SOM.Analyzed the basic principle of measuring soil organic matter base on spectral method. Introduced the latest status of soil organic matter gauge.(2) Collected 15 soil samples back to sieve, drying and label, then selected 6 typical samples to detected by the FieldSpec3 spectrometers. Analyzed the one dimensional spectrogram and concluded that the higher soil organic matter content, the absorbance value is also bigger. We also found that 450-680 nm is sensitive wave bands of soil organic matter.(3)We tried to use the Two-dimensional correlation spectroscopy technique to find some information hidden in the soil reflective spectrum. Found that the highest correlation wave bands between spectral reflectance and SOM content is around 600nm,which provided a theoretical basis for further development of portable detector of soil organic matter.(4)The first generation of portable soil organic matter detector selected the LED as light source. The Basic principle of the instrument is portable, low power consumption and high efficiency. so we chose small size, high brightness, long life, low cost LED as light source and used the high sensitivity, low dark current TSL253 as light detector. We selected a Y type optical fiber for light transmission.The instrument is consist of a optical system and a electrical system. The LED light source, optical fiber, photoelectric detector formed the light system. Signal amplifying circuit, A/D conversion circuit,1602 liquid crystal display module formed the electrical system.(5) In order to prevent the influence of natural light outside, we did the experiment in a special darkroom. The repetition error of the system is 1.13%, meet the requirements of general portable instrument. we built the regression model of linear with the actual value and self-developed instrument measured value. Correctly predicted the five other soil sample’s SOM content.