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Shigemasu R, Teraoka Y, Ota S, Hirano H, Yasutomi K, Kawahito S, Futagawa M. Development of a Current Injection-Type Impedance Measurement System for Monitoring Soil Water Content and Ion Concentration. SENSORS (BASEL, SWITZERLAND) 2022; 22:3509. [PMID: 35591198 PMCID: PMC9106015 DOI: 10.3390/s22093509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 04/24/2022] [Accepted: 05/01/2022] [Indexed: 06/15/2023]
Abstract
This study was conducted with the aim of developing a circuit system that enables the measurement of the moisture content and ion concentration with a simple circuit configuration. Our previous studies have shown that soil can be represented by an equivalent circuit of a parallel circuit of resistors and capacitors. We designed a circuit that can convert the voltage transient characteristics of the soil when a current is applied to it into a square wave and output frequency information and developed an algorithm to analyze the two types of square waves and calculate R and C. Normal operation was confirmed in the range of 10 kΩ-1 MΩ for the designed circuit, and the calculation algorithm matched within a maximum error of 5%, thus confirming the validity of the program. These successfully confirmed the changes in the water content and ionic concentration. The soil moisture content measurement succeeded in measuring a maximum error of about 10%, except at one point, and the soil ion concentration measurement succeeded in measuring a maximum error of 6.6%. A new, simple, noise-resistant moisture content and ion concentration measurement circuit system with square wave output has been realized.
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Affiliation(s)
- Ryuki Shigemasu
- Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan; (R.S.); (Y.T.)
| | - Yuki Teraoka
- Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan; (R.S.); (Y.T.)
| | - Satoshi Ota
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan; (S.O.); (H.H.); (K.Y.); (S.K.)
| | - Harutoyo Hirano
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan; (S.O.); (H.H.); (K.Y.); (S.K.)
| | - Keita Yasutomi
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan; (S.O.); (H.H.); (K.Y.); (S.K.)
| | - Shoji Kawahito
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan; (S.O.); (H.H.); (K.Y.); (S.K.)
- Research Division, Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan
| | - Masato Futagawa
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan; (S.O.); (H.H.); (K.Y.); (S.K.)
- Research Division, Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan
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Shen S, Guo P, Wu J, Ding Y, Chen F, Meng F, Xu Z. Optimized inside-out magnetic resonance probe for soil moisture measuring in situ. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 307:106565. [PMID: 31404875 DOI: 10.1016/j.jmr.2019.07.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 07/23/2019] [Accepted: 07/24/2019] [Indexed: 06/10/2023]
Abstract
We report a novel inside-out NMR (nuclear magnetic resonance) probe for the measurement of soil moisture. The probe consists of a dumbbell-shape magnet and an opposed-solenoid RF (radio frequency) coil. Optimization methods for the structure of the magnet and RF coil that maximize the SNR (signal-to-noise ratio) of NMR measurements are also described. The dumbbell-shape magnet consists of three cylindrical magnets in series whose magnetic field was calculated with analytic expression deduced by converting magnet to equivalent magnetization current on its cylindrical surface. Based on the analytic expression, a nonlinear optimization mathematical model was built to determine the optimal structure parameters automatically. The opposed-solenoid is a pair of reverse-connected solenoids and used as RF coil on inside-out NMR probe in this work. Its structure-parameter optimization was carried out based on FEM (finite element method) simulation, and UD (uniform design) was applied to increase the optimization efficiency. A prototype was designed and built consisting of a magnet with length of 100 mm and a diameter of 40 mm. An NMR-based soil moisture measuring experiment was conducted by this prototype, with NMR performed using the CPMG (Carr-Purcell-Meiboom-Gill) pulse sequence for soil sample in different moisture content. The T2 distribution spectrum reveals that there are two compartments of water in the soil sample: free water and bound water.
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Affiliation(s)
- Sheng Shen
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Pan Guo
- School of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, China
| | - Jiamin Wu
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Ye Ding
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Fangge Chen
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Fanqin Meng
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Zheng Xu
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China.
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