Design and Experiments of Nondestructive Moisture Content Testing System Based on Near-infrared Spectroscopy

doi:10.11924/j.issn.1000-6850.casb2023-0171

Abstract

Abstract:

The moisture content of corn leaves is an important physiological index in the process of crop growth. Near-infrared moisture meter can effectively detect the moisture content of corn leaves. Since the traditional near- infrared moisture meter has the disadvantages of high power consumption and high cost, we design a portable near-infrared crop leaf moisture nondestructive testing system based on STM32 by using a LED light source with 1450 nm. First, we designed the testing system consisting of light source circuit, signal processing circuit, STM32 minimum system, power circuit, etc. Then the calibration of the system was performed, which included collecting the reflected light and water content of the leaves, establishing linear fitting model of leaf water content and light segment. Finally, the portable moisture detector was tested to measure and display the leaf moisture content in real time. The results shows that the correlation coefficient of leaf moisture content and light absorption of the portable moisture detector is 0.8019 with RMSEC of 0.51, and the maximum measurement error of the test set is 1.80%, and the average measurement error is 0.964%, which meet the need of agricultural industry. This system has the advantages of fast detection speed, small size and low cost, which provides theoretical reference and technical support for the study of near infrared spectrum detection instruments.

Key words: near-infrared spectroscopy, nondestructive testing, maize leaves, moisture content, STM32

GUO Xindong, SUN Yu, ZHANG Yongmei. Design and Experiments of Nondestructive Moisture Content Testing System Based on Near-infrared Spectroscopy[J]. Chinese Agricultural Science Bulletin, 2023, 39(19): 153-158.

Figures/Tables 9

References 26

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符号	引脚	描述
5V	第17脚	降压后的5 V电源相连给单片机供电
3V	第16脚	产生3.3 V的电压给显示屏供电
B4~7	第12~15脚	分别连接显示屏的输入端
A1	第24脚	与电压跟随器的输出端相连，作为信号的输入
GND	第18脚	接地

符号	引脚	描述
5V	第17脚	降压后的5 V电源相连给单片机供电
3V	第16脚	产生3.3 V的电压给显示屏供电
B4~7	第12~15脚	分别连接显示屏的输入端
A1	第24脚	与电压跟随器的输出端相连，作为信号的输入
GND	第18脚	接地

样本集	个数	最小值/%	最大值/%	均值/%	标准偏差
建模集	40	69.81	78.70	76.53	2.25
测试集	10	72.48	80.03	76.45	2.59
总计	50	69.81	80.07	76.514	2.29

样本集	个数	最小值/%	最大值/%	均值/%	标准偏差
建模集	40	69.81	78.70	76.53	2.25
测试集	10	72.48	80.03	76.45	2.59
总计	50	69.81	80.07	76.514	2.29

编号	水分预测值	水分实测值	绝对误差
1	73.14	72.47	0.67
2	74.35	73.01	1.34
3	74.08	74.43	0.35
4	76.25	75.38	0.88
5	74.97	76.21	1.23
6	78.54	78.77	0.23
7	75.59	77.39	1.80
8	77.69	77.90	0.21
9	77.56	78.92	1.37
10	78.47	80.03	1.56