Design and Fabrication of a Soil Moisture Meter Using Thermal ...

Sensors & Transducers Volume 132, Issue 9, September 2011

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ISSN 1726-5479

Editors-in-Chief: professor Sergey Y. Yurish, tel.: +34 696067716, e-mail: [email protected] Editors for Western Europe Meijer, Gerard C.M., Delft University of Technology, The Netherlands Ferrari, Vittorio, Universitá di Brescia, Italy Editor South America Costa-Felix, Rodrigo, Inmetro, Brazil

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Schneider, John K., Ultra-Scan Corporation, USA Sengupta, Deepak, Advance Bio-Photonics, India Seif, Selemani, Alabama A & M University, USA Seifter, Achim, Los Alamos National Laboratory, USA Shah, Kriyang, La Trobe University, Australia Silva Girao, Pedro, Technical University of Lisbon, Portugal Singh, V. R., National Physical Laboratory, India Slomovitz, Daniel, UTE, Uruguay Smith, Martin, Open University, UK Soleymanpour, Ahmad, Damghan Basic Science University, Iran Somani, Prakash R., Centre for Materials for Electronics Technol., India Srinivas, Talabattula, Indian Institute of Science, Bangalore, India Srivastava, Arvind K., NanoSonix Inc., USA Stefan-van Staden, Raluca-Ioana, University of Pretoria, South Africa Stefanescu, Dan Mihai, Romanian Measurement Society, Romania Sumriddetchka, Sarun, National Electronics and Computer Technology Center, Thailand Sun, Chengliang, Polytechnic University, Hong-Kong Sun, Dongming, Jilin University, China Sun, Junhua, Beijing University of Aeronautics and Astronautics, China Sun, Zhiqiang, Central South University, China Suri, C. Raman, Institute of Microbial Technology, India Sysoev, Victor, Saratov State Technical University, Russia Szewczyk, Roman, Industrial Research Inst. for Automation and Measurement, Poland Tan, Ooi Kiang, Nanyang Technological University, Singapore, Tang, Dianping, Southwest University, China Tang, Jaw-Luen, National Chung Cheng University, Taiwan Teker, Kasif, Frostburg State University, USA Thirunavukkarasu, I., Manipal University Karnataka, India Thumbavanam Pad, Kartik, Carnegie Mellon University, USA Tian, Gui Yun, University of Newcastle, UK Tsiantos, Vassilios, Technological Educational Institute of Kaval, Greece Tsigara, Anna, National Hellenic Research Foundation, Greece Twomey, Karen, University College Cork, Ireland Valente, Antonio, University, Vila Real, - U.T.A.D., Portugal Vanga, Raghav Rao, Summit Technology Services, Inc., USA Vaseashta, Ashok, Marshall University, USA Vazquez, Carmen, Carlos III University in Madrid, Spain Vieira, Manuela, Instituto Superior de Engenharia de Lisboa, Portugal Vigna, Benedetto, STMicroelectronics, Italy Vrba, Radimir, Brno University of Technology, Czech Republic Wandelt, Barbara, Technical University of Lodz, Poland Wang, Jiangping, Xi'an Shiyou University, China Wang, Kedong, Beihang University, China Wang, Liang, Pacific Northwest National Laboratory, USA Wang, Mi, University of Leeds, UK Wang, Shinn-Fwu, Ching Yun University, Taiwan Wang, Wei-Chih, University of Washington, USA Wang, Wensheng, University of Pennsylvania, USA Watson, Steven, Center for NanoSpace Technologies Inc., USA Weiping, Yan, Dalian University of Technology, China Wells, Stephen, Southern Company Services, USA Wolkenberg, Andrzej, Institute of Electron Technology, Poland Woods, R. Clive, Louisiana State University, USA Wu, DerHo, National Pingtung Univ. of Science and Technology, Taiwan Wu, Zhaoyang, Hunan University, China Xiu Tao, Ge, Chuzhou University, China Xu, Lisheng, The Chinese University of Hong Kong, Hong Kong Xu, Sen, Drexel University, USA Xu, Tao, University of California, Irvine, USA Yang, Dongfang, National Research Council, Canada Yang, Shuang-Hua, Loughborough University, UK Yang, Wuqiang, The University of Manchester, UK Yang, Xiaoling, University of Georgia, Athens, GA, USA Yaping Dan, Harvard University, USA Ymeti, Aurel, University of Twente, Netherland Yong Zhao, Northeastern University, China Yu, Haihu, Wuhan University of Technology, China Yuan, Yong, Massey University, New Zealand Yufera Garcia, Alberto, Seville University, Spain Zakaria, Zulkarnay, University Malaysia Perlis, Malaysia Zagnoni, Michele, University of Southampton, UK Zamani, Cyrus, Universitat de Barcelona, Spain Zeni, Luigi, Second University of Naples, Italy Zhang, Minglong, Shanghai University, China Zhang, Qintao, University of California at Berkeley, USA Zhang, Weiping, Shanghai Jiao Tong University, China Zhang, Wenming, Shanghai Jiao Tong University, China Zhang, Xueji, World Precision Instruments, Inc., USA Zhong, Haoxiang, Henan Normal University, China Zhu, Qing, Fujifilm Dimatix, Inc., USA Zorzano, Luis, Universidad de La Rioja, Spain Zourob, Mohammed, University of Cambridge, UK

Sensors & Transducers Journal (ISSN 1726-5479) is a peer review international journal published monthly online by International Frequency Sensor Association (IFSA). Available in electronic and on CD. Copyright © 2011 by International Frequency Sensor Association. All rights reserved.

Sensors & Transducers Journal

Contents Volume 132 Issue 9 September 2011

www.sensorsportal.com

ISSN 1726-5479

Research Articles Gas Sensors Based on Inorganic Materials: An Overview K. R. Nemade .....................................................................................................................................

1

Control Valve Stiction Identification, Modelling, Quantification and Control - A Review Srinivasan Arumugam and Rames C. Panda.....................................................................................

14

Numerical Prediction of a Bi-Directional Micro Thermal Flow Sensors M. Al-Amayrah, A. Al-Salaymeh, M. Kilani, A. Delgado .....................................................................

25

The Linearity of Optical Tomography: Sensor Model and Experimental Verification Siti Zarina Mohd. Muji, Ruzairi Abdul Rahim, Mohd Hafiz Fazalul Rahiman, Zulkarnay Zakaria, Elmy Johana Mohamad, Mohd Safirin Karis ......................................................................................

40

Structure Improvement and Simulation Research of a Three-dimensional Force Flexible Tactile Sensor Based on Conductive Rubber Shanhong Li, Xuekun Zhuang, Fei Xu, Junxiang Ding, Feng Shuang, Yunjian Ge ...........................

47

Modeling and Simulation of Wet Gas Flow in Venturi Flow Meter Hossein Seraj, Mohd Fuaad Rahmat, Marzuki Khaled, Rubiyah Yusof and Iliya Tizhe Thuku .........

57

Improvement Study of Wet Nitrocellulose Membranes Using Optical Reflectometry Hariyadi Soetedjo ...............................................................................................................................

69

Use of Balance Calibration Certificate to Calculate the Errors of Indication and Measurement Uncertainty in Mass Determinations Performed in Medical Laboratories Adriana Vâlcu .....................................................................................................................................

76

Improved Web-based Power Quality Monitoring Instrument I. Adam, A. Mohamed and H. Sanusi .................................................................................................

89

Design and Fabrication of a Soil Moisture Meter Using Thermal Conductivity Properties of Soil Subir Das, Biplab Bag, T. S. Sarkar, Nisar Ahmed, B. Chakraborty ..................................................

100

Numerical Study of Mechanical Stirring in Case of Yield Stress Fluid with Circular Anchor Impeller Brahim Mebarki, Belkacem Draoui, Lakhdar Rahmani, Mohamed Bouanini, Mebrouk Rebhi, El hadj Benachour ..............................................................................................................................

108

Computer Vision Based Smart Lane Departure warning System for Vehicle Dynamics Control Ambarish G. Mohapatra .....................................................................................................................

122

Simple Implementation of an Electronic Tongue for Taste Assessments of Food and Beverage Products Abdul Hallis Abdul Aziz, Ali Yeon Md. Shakaff, Rohani Farook, Abdul Hamid Adom, Mohd Noor Ahmad and Nor Idayu Mahat...........................................................................................

136

Aluminum-Selective Electrode Based on (1E,2E)-N1,N2- dihydroxy )-N1,N2- bis (4-hydroxy phenyl) Oxalimidamide as a Neutral Carrier Aghaie M., Esfandyar Baghdar, Fekri Lari F., Ali Kakanejadifard, Aghaie H. ....................................

151

Authors are encouraged to submit article in MS Word (doc) and Acrobat (pdf) formats by e-mail: [email protected] Please visit journal’s webpage with preparation instructions: http://www.sensorsportal.com/HTML/DIGEST/Submition.htm International Frequency Sensor Association (IFSA).

Sensors & Transducers Journal, Vol. 132, Issue 9, September 2011, pp. 100-107

Sensors & Transducers ISSN 1726-5479 © 2011 by IFSA http://www.sensorsportal.com

Design and Fabrication of a Soil Moisture Meter Using Thermal Conductivity Properties of Soil 1

Subir DAS, 2Biplab BAG, 3T. S. SARKAR, 4 Nisar AHMED, 5B. CHAKRABORTY

1, 2, 3

Department of Instrumentation Engineering, Murshidabad College of Engineering & Technology, West Bengal, India 4 Al Habeeb College of Engineering & Technology, Hyderabad, India 5 Faculty of Agricultural Engineering, B.C.K.V., Mohanpur, West Bengal, India E-mail: [email protected] [email protected] [email protected]

Received: 23 July 2011 /Accepted: 19 September 2011 /Published: 27 September 2011

Abstract: Study of soil for agricultural purposes is one of the main focuses of research since the beginning of civilization as food related requirements is closely linked with the soil. The study of soil has generated an interest among the researchers for very similar other reasons including understanding of soil water dynamics, evolution of agricultural water stress and validation of soil moisture modeling. In this present work design of a soil moisture measurement meter using thermal conductivity properties of soil has been proposed and experimental results are reported. Copyright © 2011 IFSA. Keywords: Soil, Agriculture, Thermal conductivity, Soil moisture.

1. Introduction Soil moisture refers to the quantity of water contained of soil. Water content is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from zero (completely dry) to the value of the materials porosity at saturation. The soil moisture is a very important factor in the field of agriculture. If moisture goes below the wilting point (wilting point (WP) is defined as the minimal point of soil moisture the plant requires not to wilt) or any lower point a plant wilts and can no longer recover its turgidity when placed in a saturated atmosphere for 12 hours.

100


The soil moisture sensor is connected to irrigation system controller that measures soil moisture content in the active root zone before each schedule irrigations that is soil moisture sensors measures real time soil moisture. For the growing of crop three factors are most important first the soil nutrients and soil properties; second the properties of the seeds that used to grow and most important is the soil moisture level. If the soil moisture goes down despite having good seeds and full nutrient soil we loss the crop. Knowledge of the spatial distribution in soil moisture content for the top 1 to 2 m of the earth’s surface, known as the root zone, is important for under-standing meteorological, hydrologic, and agronomic processes. However, soil moisture is highly variable in space and time because of soil, topography, land cover, evapo-transpiration, and precipitation heterogeneity. Moisture takes some heat thus it helps to balance the temperature of the ground also it loses the soil clods which helps in penetrating the roots of the crop. The micro organism activity increases as the moisture content increase which balances nutrients in the soil. Different workers [1-11] have worked on different technique of soil moisture sensors. A soil moisture transmitter based on gypsum block sensor has been developed by Irrometer Company, Riverside [7], which is mainly fine aggregates mixed with gypsum buffer, held inside a permeable membrane and a perforated stainless steel sleeve. Electrodes are embedded in the granular matrix, and the electrical conductance between them is the parameter measured. Conductance increases with increasing soil moisture. The purpose of the gypsum is to buffer the measurement from ions that are found in uncontrolled amounts in the soil. Majid et al. [8] design soil moisture capacitive sensor interface circuit based on phase differential technique, according to them the circuit has been designed and fabricated using MIMOS’ 0.35"m CMOS technology. Simulation and test results show linear characteristic from 36 – 52 degree phase difference, representing 0 – 100 % in soil moisture level. Test result shows the circuit has sensitivity of 0.79 mV/0.10 phase difference, translating into resolution of 10 % soil moisture level. A Wireless soil moisture sensor based on Fringing Capacitance has been designed by Wobschall et. al. [3], which based on mixtures of dielectric particles which are conducting. Dielectric constant is dependent on moisture content by volume. University of Florida [9] worked on the development of a soil moisture sensor with an objective to measure soil moisture at the root zone and regulates the existing conventional irrigation timer, resulting in considerable water savings when installed and used properly. Khan et al. [6] designed a high accuracy measurement circuit, employing a bridge amplifier, an integrator, and a comparator, for detecting the moisture content of soil. This circuit has the advantage of detecting soil resistance with better accuracy and with wide-range linearity. Davis, Johnson and Huberts [7] jointly studied and invented a soil moisture sensor which includes a processor to derive soil moisture values and a memory store associated with said processor to store measured values on a periodic basis, wherein the processor scales the stored moisture values to establish a moisture range for the sensor that can be used to calibrate each new reading. The artificial application of water is called irrigation which is essential for growing of high yield crop. So measurement and analysis of soil moisture content is important factor in the field of agriculture. The current moisture measurement techniques are costly and out of reach of the poor farmers. Here a low cost device for measurement of soil moisture level has been proposed. The detailed research work is under progress and the observation from the preliminary work has been reported here. This circuit has the advantage of detecting soil moisture with better accuracy and linearity when compared with other works. Also cost of this proposed meter will be less.

2. Theoretical Background Thermal conductivity of soil measures the heat flow through the particles that comprise the soil. It is regulated mainly by water content and there is much variation for different types of soil. In soil physics, the thermal properties reflect how heat is transferred through the soil by conduction, convection and radiation. Thermal conductivity is measured in watts (W) per Kelvin per meter. 101


2.1. Factors Influencing Thermal Conductivity in Soils A variety of factors influence the heat flux through soil. The primary influences are the soil's moisture content and its dry density. Other parameters that have a secondary effect are soil type or mineral composition, dry density of the soil, temperature, texture and time. Soil is composed of weathered rock particles, water, and void spaces. The void spaces are very important in thermal conduction. They are not really empty like a vacuum but always contain either air or water. Air is a poor conductor of heat because the gas molecules are spaced far apart and do not physically contact one another. Water is an excellent thermal conductor because it's a liquid and there's more particle contact in the void spaces between soil particles and water. That heat energy is passed along through this medium in the voids until it contacts solid soil particles which absorb and move the thermal energy.

2.1.1. Soil Moisture and Dry Density The consolidation of the soil determines its dry density. As soil becomes more compacted, the void spaces are reduced and air is squeezed out. With further consolidation, water flows into the smaller void spaces and the soil becomes more saturated as its density increases. As the soil moisture or the density of the soil increases, its thermal conductivity also increases. Saturation describes the amount of water present in the soil. An unsaturated soil still has air in the void spaces and its thermal conductivity is less than that of saturated soil. The dry density parameter refers to the mass of soil particles per unit volume and reflects a measure of the particle contact in the soil.

2.1.2. Moisture Content of the Soil As the saturation levels of a soil increase, the thermal conductivity of the soil also increases. Moisture only partially coats the soil particles at low saturation levels. With more water, the void gaps between the particles begin filling and the thermal conductivity continues to rise accordingly. As the one hundred percent saturation level of the soil is approached, the voids fill completely and the heat flux or the thermal conductivity reaches its highest flow for that soil sample. A saturated soil has a thermal conductivity level near that of pure water.

2.1.3. Soil Types and Composition There are several different soil types: gravels, sands, silts, clays, and soil containing organic materials or peat. Whether or not these soils are in a frozen or a thawed state will also affect their thermal conductivity. As the organic content of the soil increases, the thermal conductivity generally decreases because organics don't carry a heat flux very well. However, the peat is decomposing and giving off heat in that process so peat bogs can be very warm. Even if a soil has high moisture content, it may not necessarily mean that the soil will warm up faster than a dry soil. Evaporation plays a role in removing much of the solar energy before the soil can warm up. So dry soils warm up faster under the sun but they cool more quickly at night. Soils with high moisture content evaporate the water and the soil doesn't warm as fast during the day but it cools more slowly at night because of the higher moisture content.

102


2.1.4. Other Factors In agriculture, the soil's microclimate which nourishes seeds is determined through the thermal conductivity of the soil and its moisture content. This determines the early growth and development of a crop. The microclimate influences seed germination, seedling growth and establishment of the crop. Research has shown that increasing the percentage of organic content in the soil decreases the thermal conductivity. In hot areas, adding mulch or other organic components to the soil will help prevent seeds from baking under intense temperatures.

3. Experiment Set-Up In a circular shape hollow pipe made of PVC material and tightly closed at one side a CL-100 transistor with emitter base shorted is connected as a source of heat and a temperature sensor (AD590) has been connected, 1.27 cm (arbitrarily selected) distance apart as a detector of heat as shown in Fig. 1, Fig. 2 and Fig. 3. Now hollow pipe has been filled up with sample (soil) for which moisture level has to measure. The output of the temperature sensor (AD620) that is output from the detector is then converted to voltage using a current to voltage (I-V) converter. The output from the I-V converter is send to an amplifier circuit for proper amplification and acquisition. The output of the amplifier circuit is calibrated in such a way that 1mV is equal to 10C. The experiment has been performed for several times and good results have been obtained in each time.

Fig. 1. Schematic diagram of the complete system.

Fig. 2. Developed sensor. 103


Fig. 3. Experimental setup.

4. Experiment and Results Several experiments has been performed on locally available soil (mainly clay type) and found a good results comparing with the slandered available method. The output current signal from the sensor is then converted into voltage signal using an I-V converter. The millivolt signal from the I-V converter is recorded. The output is calibrated in such a way that 10 C is equivalent to 1 mv. The soil has been selected arbitrarily from the local area and experiment has been performed on this soil sample. By using the standard available method the soil moisture has been calculated on dry basis and after that soil has been tested by newly proposed soil moisture meter. The experimental data has been recorded for a fixed time for different soil sample in a regular time interval. Time verses output voltage (from the sensor) plot has been drawn for each and every soil sample and almost a linear curve has been observed. The experimental graph has been shown in Figs. 4-7. Finally percentage of soil moisture verses measured voltage graph has been drawn and a good linearity has been found as shown in Fig. 8. 140

Time (in S ec)

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Fig. 4. Sample-I (9 % moisture dry basis): observed Voltage vs. Time. 104


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Fig. 5. Sample-II (10% moisture dry basis): observed Voltage vs. Time.

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Fig. 6. Sample-III (12.5 % moisture dry basis): observed Voltage vs. Time.

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26

26.5

Obse rve d V olta g e (in m V)

Fig. 7. Sample-IV (16.6 % moisture dry basis): observed Voltage vs. Time.

105

Measured Voltage in mV


35 30 25 20 15 10 5 0 0

10

20

30

% of Soil Moisture (DB)

Fig. 8. % soil moisture vs. Measured Voltage in mV.

5. Discussions The results obtained by the proposed measuring circuit has been presented, which demonstrate that the change in voltage from the sensor output is mostly linear with the moisture content. Output voltage is increasing with the increase of soil moisture. This is due to the fact that when moisture content is increasing in the soil the void space is filled up and thermal conductivity is increasing accordingly. The cost of the total system is very low, so that it can be easily affordable but the whole assembly has to be tested and proper calibration has to be done with more samples and more observation. Here we use only one particular soil sample. We have presented only very preliminary results; the research on this line is in progress.

Acknowledgement The authors are thankful to Bidhan Chandra Krishi Viswa Vidyalaya and Murshidabad College of Engineering and Technology for providing the facilities to carry out this research work.

Reference [1]. Walker, Jeffrey P. and Houser, Paul R., Evaluation of the Ohmmapper Instrument for Soil Moisture Measurement, Soil Science Society of American Journal, Vol. 66, 2002, pp. 728-734. [2]. Lloyd, C. R., The Application of an instrument for non-destructive measurements of soil temperature and Resistance profile at a high Arctic field site, Hydrology and Earth System Science, Vol. 2, 1, 1998, pp. 121-128. [3]. Jager, J. M. de and Charles-Edwards, Jenifer, Thermal Conductivity Probe for Soil-moisture Determinations, J. Exp. Bot., Vol. 20, 1, 1969, pp. 46-51. [4]. Nakshabandi, G. Al and Kohnke, H., Thermal conductivity and diffusivity of soils as related to moisture tension and other physical properties, Agricultural Meteorology, Vol. 2, Issue 4, August 1965, pp. 271-279. [5]. Wobschall, D., A Frequency Shift Dielectric Soil Moisture Sensor, IEEE Geosci. Electronics, Vol. GE16, 1978, pp. 112-118. [6]. Wobschall D, A Theory of the Complex Dielectric Permittivity of Soil Containing Water: The SemiDisperse Model, IEEE Geo. Trans., 15, 1977, pp. 49-58. [7]. Electrical Interface for Watermark™ or Gypsum Block Sensors, Irrometer Company, Riverside CA, 951/689-170. [8]. Majid, H. A., N. Razali, Sulaiman, M. S., and A’ain A. K., World Academy of Science, Engineering and Technology, Vol. 55, 2009, pp. 636-639. 106


[9]. University of Florida—Program for Resource Efficient Communities, Florida Field Guide to Low Impact Development, University of Florida, IAFS Extension. [8]. Khan, Sheroz, Alam, A. H. M. Zahirul, Khalifa, Othman O., Islam, Mohd Rafiqul, Zainudin, Zuraidah, Khan, Muzna S., and Pauzi, Nurul Iman Muhamad, A High Accuracy Measurement Circuit for Soil Moisture Detection, International Journal of Mathematical, Physical and Engineering Sciences, Vol. 02, No. 2, 2008, pp. 59-62. [9]. Wireless Leaf & Soil Moisture/Temperature Station, Vantage Pro2TM Accessories, www.davisnet.com. [10].World Intellectual Property Organization (WIPO) IP Services. (WO/2007 /002994), Soil Moisture Sensor, http://www.wipo.Int /pctdb /en /wo.jsp?WO=20 07002994 [11].Cardell-oliver, Rachel, Kranz, Mark, Smettem, Keith, Mayer, Kevin, A Reactive Soil Moisture Sensor Network: Design and Field Evaluation, International Journal of Distributed Sensor Networks, Vol. 1, 2005, pp. 149–162. ___________________ 2011 Copyright ©, International Frequency Sensor Association (IFSA). All rights reserved. (http://www.sensorsportal.com)

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