Development Of Optical Detection Instrument For Nitrogen Content Of Leaves

Nitrogen is one of the important nutrient elements in plant growth and development,and it is important to develop plant nitrogen detection instrument.Using the Normalized Difference Greenness Index(NDGI)of 565 and 760 nm optical bands,a portable optical instrument for measuring nitrogen content in leaves was developed.The main research and achievements are as follows:1)The hardware of the system mainly includes signal acquisition unit,main control unit,communication unit,support unit and power unit.The system is based on STM32F373RCT6 main control chip.It uses lithium battery as power supply,illuminates the blades by LED light source driving circuit,and receives the reflected light from the blades by silicon photovoltaic cells.The signal is sent to SDADC module of the main control chip.It uses I-V conversion circuit and conditioning circuit for nitrogen content detection.Configuration of real-time clock,storage,display and other supporting circuits is used to improve the instrument function.The hardware uses serial module and bluetooth module to interact with the host computer.2)The system software includes three parts: master control program of hardware,Windows form application program on computer side and APP program on mobile phone side.Master control program uses menu,including measurement,browsing,deletion and other functions.The software of computer and mobile terminal uses data transmission unit and data display unit to establish data management function.3)The hardware and software are tested.Hardware equipment testing includes power supply,communication,storage and other major module testing;PC software testing includes data interaction,data display and other functions testing.The test results show that the functions of the hardware and the software are normal.The indirect calibration experiment was carried out by N-PEN N110 instrument,and the calibration results were input into the lower computer program.The nitrogen content in leaves was measured by N-PEN N110 instrument and the leaf nitrogen meter in this paper.The R2 index of nitrogen content data of the two devices is 0.984,the correlation is high,the average error is 6.54%.Ten times of measuring nitrogen content at the same location,the difference of data is 0.384%,which accounts for a small proportion of the total.The average value of data is 12.4119%,and the standard deviation of experiment is 0.121%.It shows that the portable optical nitrogen measurement prototype of blade developed in this paper realizes the fast detection work of nitrogen content of blade based on non-destructive spectroscopy technology.This system can meet the application needs.