基于光谱技术的植物叶绿素浓度无损检测仪器的研制

开发了一种便携式植物叶绿素无损检测仪器，该仪器可实现对叶绿素浓度的实时、快速、无损检测。仪器主要包括4个部分：叶片夹具，光源驱动电路，光电检测及信号调理电路和微控制系统。提出了一种电流可调节的光源恒流驱动电路方案，在实现恒流驱动的同时还可以对驱动电流进行程控。同时提出了一种一体化叶片夹具设计方案，不仅简化了仪器的光学结构，而且提高了仪器稳定性。在仪器的标定实验中，用SPAD-502叶绿素测量仪测定的叶片叶绿素含量SPAD值作为标准值，建立了多元线性标定模型，对仪器的性能进行了评价，叶绿素预测值与标准值的相关系数为0.97，预测均方根误差为1.3 SPAD，仪器重复性的均方根误差为0.1 SPAD。标定实验结果表明，该仪器测量精度高、性能稳定。

Development of Chlorophyll Concentration Nondestructive Measurement Instrument Based on Spectral Analysis Technology

A portable nondestructive measuring instrument for plant chlorophyll was developed, which can perform real-time, quick and nondestructive measurement of chlorophyll. The instrument is mainly composed of four parts, including leaves clamp, driving circuit of light source, photoelectric detection and signal conditioning circuit and micro-control system. A new scheme of light source driving was proposed, which can not only achieve constant current, but also control the current by digital signal. The driving current can be changed depending on different light source and measurement situation by actual operation, which resolves the matching problem of output intensity of light source and input range of photoelectric detector. In addition, an integrative leaves clamp was designed, which simplified the optical structure, enhanced the stability of apparatus, decreased the loss of incident light and improved the signal-to-noise ratio and precision. The photoelectric detection and signal conditioning circuit achieve the conversion between optical signal and electrical signal, and make the electrical signal meet the requirement of AD conversion, and the photo detector is S1133-14 of Hamamatsu Company, with a high detection precision. The micro-control system mainly achieves control function, dealing with data, data storage and so on. As the most important component, microprocessor MSP430F149 of TI Company has many advantages, such as high processing speed, low power, high stability and so on. And it has an in-built 12 bit AD converter, so the data-acquisition circuit is simpler. MSP430F149 is suitable for portable instrument. In the calibration experiment of the instrument, the standard value was measured by chlorophyll meter SPAD-502, multiple linear calibration models were built, and the instrument performance was evaluated. The correlation coefficient between chlorophyll prediction value and standard value is 0. 97, and the root mean square error of prediction is about 1.3 SPAD. In the evaluation experiment of the instrument repeatability, the root mean square error is 0. 1 SPAD. Results of the calibration experiment show that the instrument has high measuring precision and high stability.