Research On Near-infrared Light Measuring Water Content Of Plant Leaves Based On Pseudo-random Sequence Modulation

In recent years,with the rapid development of technology and economy,people have become increasingly demanding for agricultural products.In the context of water scarcity,it is particularly important that how dose control the surrounding environment caused by changes in the water content of the plant really-time,to achieve precision irrigation,and to improve the yield and quality of crops further.Because the leaves are the main organs of the water content of plant,therefore,we can achieve the purposes for the status monitor plant growth and precision irrigation by measuring the water content of plant leaves.Based on this,this thesis presents the research and design of new blade plant water content measurement device that is portable and high-precision.After analyzing the advantages and disadvantages of domestic and international plant leaves water content measurement method currently,this thesis presents the measurement system that near-infrared light measuring water content of plant leaves based on the pseudo-random sequence M modulation.First,the basic theories of water measurement were described;secondly,the pseudo-random sequence of M modulats near-infrared light detection principle was studied detailed;finally,the portable and high-precision water content measuring instrument of plant leaves was designed based on STM32F103 master controller.In order to realized the measurement functions,in the hardware section,the basic light distribution structure,power modules,pre-amplifier,filter amplifier circuit,demodulation circuit,data acquisition circuit and TFT display circuit were designed;in the software part,programs of the pseudo-random sequence of M,data acquisition and storage,related(?)In the experimental study,first,we designed Matlab simulation that the system noise and interference suppression effect was best when we selected the signal period N = 255 of the pseudo-random sequence M;secondly,the detector data corresponding calibration experiments was designed,while we compared measuring output characteristic and repeatability of plant leaves water content at three different light sources incentives:the DC law,PWM modulation and pseudo-random sequence M;finally,the influence of the ambient light and other factors on the measurement results was analyzed.Experimental results showed that the pseudo-random sequence of M modulation measurement method can well suppress the interference of ambient light,and the system has the higher practical value.Therefore,the M pseudo-random sequence modulation type plant leaf water content measurement system can better solve the problems of the ambient light and insufficient degree of measurement equipment portability.This thesis can achieve the purpose of the research on the water content measurement system of plant leaves.