Abstract:To determine reasonable detecting frequency for developing soil′s moisture sensor based on dielectric properties and to reduce influence of temperature on permittivities, Lou soil in Guanzhong Plain, Shaanxi Province, was used to study the influence of frequency(10-4 500 MHz), moisture content(9%-25%)and temperature(5-50 ℃)on relative dielectric constant and dielectric loss factor by network analyzer and coaxial-line probe technology. The reasons why permittivities changed with these factors were analyzed, and the frequency-, moisture content- and temperature-dependent penetration depth was determined. The results show that with the increasing of frequency from 10 MHz to 4 500 MHz, the relative dielectric constant decreases, while the dielectric loss factor changes from increasing to decreasing then to increasing. Both dielectric constant and loss factor increase with increasing moisture content and temperature over the detected ranges. The penetration depth decreases with increasing frequency, moisture content and temperature. Frequency, moisture content and temperature are major factors which influence dielectric permittivities and penetration depth of soil. The study indicates that the reasonable frequencies for detecting moisture content of soil based on dielectric properties are over the frequency range from 50 MHz to 100 MHz.
郭文川,, 张鹏, 宋克鑫, 韩文霆,, 许景辉. 塿土介电特性与水分检测频率及温度影响[J]. 排灌机械工程学报, 2013, 31(8): 713-718.
Guo Wenchuan,, Zhang Peng, Song Kexin, Han Wenting,, Xu Jinghui. Dielectric properties of Lou soil and moisture content detection affected by frequency and temperature. Journal of Drainage and Irrigation Machinery Engin, 2013, 31(8): 713-718.
[1]邹维. 土和土壤的工程名称与分类及使用区别[J].水土保持应用技术,2010,26(2): 26-27. Zou Wei. The engineering name classification and use difference of soil[J]. Technology of Soil and Water Conservation, 2010, 26(2): 26-27.(in Chinese)[2]马红章,柳钦火,王合顺,等. 基于微波干涉技术的土壤介电特性测量[J].农业工程学报,2011,27(9): 159-163. Ma Hongzhang, Liu Qinhuo, Wang Heshun, et al. Soil dielectric characteristic determination based on microwave interferometry theory[J]. Transactions of the CS-AE, 2011, 27(9):159-163.(in Chinese)[3]王聪颖,孙宇瑞,张慧娟. 一种基于三角波窄脉冲序列的时域反射土壤水分测量方法[J].应用基础与工程科学学报,2010,18(5): 869-876. Wang Congying, Sun Yurui, Zhang Huijuan. A TDR-based method using a triangular-wave pulse train for measuring soil water content[J]. Journal of Basic Science and Engineering, 2010, 18(5):869-876.(in Chinese)[4]李加念,洪添胜,冯瑞珏,等. 基于真有效值检测的高频电容式土壤水分传感器[J].农业工程学报,2011,27(8): 216-221. Li Jianian, Hong Tiansheng, Feng Ruijue, et al. High-frequency capacitive soil water content sensor based on detecting of true root mean square[J]. Transactions of the CSAE, 2011, 27(8):216-221.(in Chinese)[5]郭文川,朱新华. 国外农产品及食品介电特性测量技术及应用[J].农业工程学报,2009,25(2): 308-312. Guo Wenchuan, Zhu Xinhua. Foreign dielectric property measurement techniques and their applications in agricultural products and food materials[J]. Transactions of the CSAE, 2009, 25(2):308-312.(in Chinese)[6]Mironov V L, Dobson M C, Kaupp V H, et al. Genera-lized refractive mixing dielectric model for moist soils[J]. IEEE Transactions on Geoscience and Remote Sensing, 2004, 42(4):773-785.[7]Chen Y P, Or D. Geometrical factors and interfacial processes affecting complex dielectric permittivity of partially saturated porous media[J]. Water Resources Research, 2006, 42(6):W06423.[8]Seyfried M S, Grant L E. Temperature effects on soil dielectric properties measured at 50 MHz[J]. Vadose Zone Journal, 2007, 6(4):759-765.[9]Lasne Y, Paillou P, Freeman A, et al. Effect of salinity on the dielectric properties of geological materials: Implication for soil moisture detection by means of radar remote sensing[J]. IEEE Transactions on Geoscience and Remote Sensing, 2008, 46(6):1674-1688.[10]Kizito F, Campbell C S, Campbell G S, et al. Frequency, electrical conductivity and temperature analysis of a low-cost capacitance soil moisture sensor[J]. Journal of Hydrology, 2008, 352(3/4):367-378.[11]Thompson R B, Gallardo M, Fernandez M D, et al. Salinity effects on soil moisture measurement made with a capacitance sensors[J]. Soil Science Society of America Journal, 2007, 71(6):1647-1657.[12]Velazquez-Marti B, Gracia-Lopez C, Plaza-Gonzalez P J. Determination of dielectric properties of agricultural soil[J]. Biosystems Engineering, 2005, 91(1): 119-125.[13]Guo Wenchuan, Zhu Xinhua, Liu Yi, et al. Sugar and water contents of honey with dielectric property sensing[J]. Journal of Food Engineering, 2010, 97(2):275-281.[14]Sacilik K, Colak A. Determination of dielectric properties of corn seeds from 1 to 100 MHz[J]. Powder Technology, 2010, 203(2):365-370.[15]宋雷,张小俊,李海鹏. 上海冻结粉质黏土介电常数的实测及规律分析(0.1~1 GHz)[J].土木工程学报,2011,44(8): 107-110. Song Lei, Zhang Xiaojun, Li Haipeng. Dielectric constant measurement and analysis of Shanghai frozen silty clay(0.1~1 GHz)[J]. China Civil Engineering Journal, 2011, 44(8):107-110.(in Chinese)[16]Guo Wenchuan, Tiwari G, Tang J, et al. Frequency, moisture and temperature-dependent dielectric properties of chickpea flour[J].Biosystems Engineering, 2008, 101(2): 217-224.[17]Guo Wenchuan, Wang Shaojin, Tiwari G, et al. Temperature and moisture dependent dielectric properties of legume flour associated with dielectric heating[J]. LWT-Food Science and Technology, 2010, 43(2): 193-201.[18]郭文川,吕峻峰, 谷洪超. 微波频率和温度对食用植物油介电特性的影响[J].农业机械学报,2009,40(8):124-129. Guo Wenchuan,Lü Junfeng,Gu Hongchao. Effect of frequency and temperature on microwave dielectric properties of edible vegetable oils[J]. Transactions of the Chinese Society for Agricultural Machinery, 2009,40(8):124-129.(in Chinese)[19]Zhu Xinhua, Guo Wenchuan, Wu Xiaoling, et al. Dielectric properties of chestnut flour relevant to drying with radio-frequency and microwave energy[J]. Journal of Food Engineering, 2012, 113(1): 143-15.[20]Guo Wenchuan, Wu Xiaoling, Zhu Xinhua, et al. Temperature-dependent dielectric properties of chestnut and chestnut weevil from 10 to 4500 MHz[J]. Biosystems Engineering, 2011, 110(3): 340-347.