Moisture Content Sensor Research Articles

Study on Runoff and Infiltration for Expansive Soil Slopes in Simulated Rainfall

In order to understand the hydrological process of expansive soil slopes, simulated rainfall experiments were conducted to study the effects of slope gradient and initial soil moisture content on runoff and infiltration for expansive soil slopes located in south China. The field program consisted of four neighboring slopes (70%, 47%, 32%, and 21%) instrumented by a runoff collection system and moisture content sensors (EC-5). Results from the monitored tests indicate that there was delay in the response of surface runoff. The runoff initiation time decreased with initial soil water content and increasing slope gradient. After the generation of runoff, the cumulative runoff per unit area and the runoff rate increased linearly and logarithmically with time, respectively. The greater the initial soil moisture content was, the smaller the influence of slope gradient on runoff. A rainfall may contribute from 39% to about 100% of its total rainfall as infiltration, indicating that infiltration remained an important component of the rainwater falling on the slope, despite the high initial soil water content. The larger the initial sealing degree of slope surface was the smaller the cumulative infiltration per unit area of the slope. However, the soil moisture reaction was more obvious. The influence of inclination is no longer discernible at high initial moisture levels. The greater the initial soil moisture content and the smaller the slope gradient, the weaker was the change of soil water content caused by simulated rainfall. The influence of initial soil moisture content and slope gradient on the processes of flow and changes of soil water content identified in this study may be helpful in the surface water control for expansive soil slopes.

Study on influence and compensation for soil compactness on volumetric water content measurement

Volumetric water content measurements based on soil dielectric properties are affected by soil compaction. Today’s commercial products produce substantial measurement error as they do not account for the influence of soil compaction. This paper presents a portable soil volumetric moisture content sensor based on the principle of standing wave rate and simultaneous soil compactness measurement. The coupling relationship between soil compactness and soil volumetric moisture content can be easily observed by converting them into polar coordinates. A modified soil volumetric moisture content model based on the soil compactness is also established to support the operation of the proposed sensor.

Performance evaluation of flexible pavements with a lateritic gravel base using accelerated pavement testing

Lateritic gravel is widely used for road construction and its mechanical properties have been explored in numerous laboratory tests. In this study, full-scale accelerated pavement testing was conducted to evaluate the long-term performance of pavements constructed with lateritic gravel as the subbase and base materials. Test Sections were constructed in a test tank and instrumented with temperature sensors, strain sensors, and moisture content sensors. This study investigated two asphalt layer thicknesses (5 cm and 10 cm) and three types of base materials (crushed stone, cement-lateritic gravel, and lateritic gravel blended with crushed stone) for comparative purposes. The test pavements all had a uniform subbase depth of 30 cm of raw lateritic gravel. The development of permanent deformation and cracking was recorded periodically. Based on measurements and observations, this study found that the crushed stone base performed better than the blended lateritic base in terms of rutting and cracking resistance and that rutting development was relatively less in the thicker (10 cm) asphalt layer than in the thinner (5 cm) layer. The cement-lateritic base developed the largest rutting and exhibited the earliest appearance of cracking among the three base types and showed the weakest behavior among these three bases.

Biochar Effects on Mineral Nitrogen Leaching, Moisture Content, and Evapotranspiration after 15N Urea Fertilization for Vegetable Crop

Globally, mineral nitrogen (N) losses as nitrate leaching (NL) are a substantial portion of applied fertilizer and cause surface and sub-surface water contamination. To precisely measure NL and its interlink parameters, biochar soil amendment was tested in this study. Three treatments—biochar (BC), without biochar (WB) with 15N urea (300 kg/ha), and control (no fertilization)—were tested in soil-filled lysimeters (circular PVC (Polyvinyl Chloride) tank of 30 cm diameter and 35 cm height) equipped with moisture content sensors and weighing assembly for the consecutive two cropping of Brassica Camprestis Var. Chinensis. The 15N-urea in the first season and the poultry manure in the second season were applied, but the fate of the 15N was examined in leachate, dry matter, and soil. As compared to WB, BC significantly decreased mineral N leaching, including nitrate levels (35%), increased electrical conductivity (68.5%), and water availability (20% inches per foot), while there was a non-significant increase in biomass per plant (2.84%), evapotranspiration (8.33%), dry matter (6.89%), and a decrease in mean leachate volume (7.63%). Moreover, BC accumulated values were higher than WB, as N uptake (38%), water use efficiency (12.24%), maximum fresh weight (11.4%), and soil N retained (185%) after cropping. The soil pH, the bulk density, and the total nitrogen were changed but presented non-significant differences. Therefore, biochar can increase soil N retention and available water to improve water use efficiency and decrease potential N leaching.

Structural health monitoring of the Holy Aedicule in Jerusalem

The Holy Aedicule situated inside the Church of the Resurrection in the Old City of Jerusalem is the holiest Christian site in the world. For ensuring the sustainability of the Holy Aedicule, continuous, as well as periodic, monitoring using advanced equipment is crucial. The structural health monitoring process, as part of an overall management plan, will contribute in real time, through appropriate risk analysis and documentation, so that all relevant Christian Communities can take appropriate measures for the preservation of the structure. This paper describes the monitoring project and the equipment installed at the site during the restoration works. Main risks identified by the diagnostic campaign were tomb microclimatic variations as a result of the enormous number of visitors and Jerusalem climatic data, rising damp, seismic hazard, and structure movements during and after the completion of the restoration works. The installed instrumentation includes air temperature and relative humidity sensors, moisture content sensors for masonry materials, and a geodetic total station and a network of accelerometers for the continuous monitoring of the static and dynamic behavior of the monument, respectively. Thus, the remote monitoring and assessment of various risks to the monument is possible in real time.

Research on dynamic compressive stress response of new type filler subgrade in freezing and thawing processes

In this study, the dynamic compressive stress (DCS) response of a new type filler subgrade, which consists of oil shale residue, silty clay and fly ash, was studied during the freezing and thawing processes. Moisture content sensor, temperature sensors and DCS sensors were embedded in the outdoor subgrade model in the seasonally frozen region. Five loading points and three levels of load were set to investigate the effects of load on the subgrade in the horizontal direction and vertical direction during the freezing and thawing processes. Furthermore, distribution characteristics of DCS were analyzed by combining with the moisture content and temperature distribution diagram. The results show that:(1) The range of horizontal DCS response fluctuated significantly during the freezing and thawing processes. The maximum value emerged in thawing period and the minimum value emerged in frozen period. (2) The vertical DCS response was strongly affected by moisture content and temperature. The maximum value of DCS, the DCS variation rate along depth and the DCS variation caused by load change all occurred in thawing period. (3) Thawing period is the most unfavorable period for subgrade in seasonally frozen regions. Thus, moisture content and temperature conditions during the thawing period must be considered while optimizing and modifying subgrade filler in seasonally frozen regions.

Experimental study on unfrozen water and soil matric suction of the aeolian sand sampled from Tibet Plateau

Aeolian sand is sometimes used as geomaterial in cold regions of China. This paper tries to investigate the unfrozen water, matric suction of aeolian sand, which is related to its thermal and mechanical properties. The pF-meter matric suction sensor coupled with 5TM moisture content sensor that can operate in the subfreezing environment was used to measure the moisture content and matric suction of aeolian sand under different conditions. Combined with thermal resistor temperature probe, the relationship between unfrozen water and temperature is analyzed. The results indicate a significant phenomenon of latent heat absorption and release at freezing and thawing points. In addition, the phenomenon of the supercooling was observed with a value of −1.96 °C during stepwise temperature change. Most water in the sand freezes at freezing point 0 °C under rapid and stepwise temperature change. There is approximately 3% of unfrozen water content retained when the sand temperature drops to −15 °C. The soil matric suction increases very slowly at the stable freezing stage. These results provide the theoretical support for future research on the moisture migration mechanism and engineering application of aeolian sand in cold regions.

Determining moisture content of Traditional Chinese Medicines using a near-infrared LED-based moisture content sensor with spectrum analysis

In Traditional Chinese Medicine (TCM), moisture content (MC) inspection using voltage level or a lock-in amplifier, with a features-based near-infrared light-emitting diode sensor is possible. Abundant absorption response in a wide frequency range and information in both the time-domain and frequency-domain can be obtained, with the square excitation method. However, planeness, heterogeneous particle sizes, and measurement noise negatively affect the time-domain feature during MC inspection. In this work, spectrum analysis (SA) for feature extraction is investigated, to precisely measure the MC of Dutong pills. The principal components for low and high frequencies, are aimed at counteracting the dimensional methods, which are used for supplying the lower dimensional features. The SA experimental results demonstrate that the low frequency components, ranging from the base to the 3rd harmonic components, have a high linear correlation with the MC. The calibration and validation experimental results reveal that the MC can be a monotonic function about the SA amplitudes or first principal component (PC1), with the proposed sensor. This method has the potential to be used for gauging automatic, in situ MCs, particularly for quality control and Process Analytical Technology in TCM. Future research opportunities include improving accuracy and application of the method under field conditions.

Smart Irrigation System: A Water Management Procedure

This paper presents a smart irrigation system suitable for use in places where water scarcity is a challenge. In many parts of Africa, even when irrigation is practiced, it is manually operated. Smart irrigation system is thereby believed to be a major solution. The paper therefore presents a smart irrigation system that optimizes the available water in the water reservoir thus providing an efficient and effective water usage solution for the irrigation system. The irrigation system is able to automatically start/stop water pumps on the irrigation site based on the soil moisture content acquired from the moisture content sensor as well as the ultrasonic sensor measuring the water level in the reservoir. The measured sensor values are sent to the Arduino microcontroller for configuring the control algorithm. The system prioritizes irrigation operation by determining the number of pumps to be operated at any instance as well as their locations. In this way, different crops can be watered depending on their varying water requirements. In order to implement the design, a laboratory scale architectural model depicting a farm setting with reservoir, direct current (DC) pumps and the control unit was constructed. Experimental results revealed good performance which makes the developed system a suitable tool for studies on irrigation.

Assessing water use and soil water balance of planted native tree species under strong water limitations in Northern Chile

Some forest plantations with native species are established in semiarid central Chile to compensate for industrial activities such as those of mining. Two of those operational forest plantations were monitored from age 1 to 3 years-old (2014–2016). Some plant attributes and soil volumetric water content (VWC) were monitored for eight native tree species (Acacia caven, Schinus polygamus, Porlieria chilensis, Lithraea caustica, Quillaja saponaria, Cryptocarya alba, Drimys winteri and Maytenus boaria), and a water balance model fitted to assess plant water use. Site preparation comprised planting holes of 40 cm × 40 cm by 50 cm in depth dug with a backhoe. Substrate was removed and mixed with compost in proportion 70:30 before mixing it in the planting hole. Planting holes acted as water reservoirs over the study period with soil VWC generally increasing with soil depth being also less variable deeper than in the upper soil layers. The ratio of adaxial (upper leaf side) to abaxial (lower leaf side) stomatal conductance approximately followed a species gradient from xeric to mesic. Irrigation represented about 26% and 53% of the total water input for the sclerophyll and the D. winteri plantation, respectively. At the plant level (0.4 × 0.4 m), soil evaporation and transpiration of D. winteri (273 and 232 mm year−1, equivalent to 43.7 and 37.1 L plant−1, respectively) were about twofold the values for the sclerophyllous/malacophyllous plantation (138 and 128 mm year−1, 22.1 and 20.5 L plant−1, respectively). We suggest the water budget for the sclerophyll/malacophyllous plantation was tight but feasible to be adjusted while for D. winteri irrigation was excessive, could be drastically reduced, and suppressed altogether if planted in gullies. We believe water balance models and soil moisture content sensors could be used to better plan and manage irrigation frequency and amounts in compensation forest plantations in semiarid central Chile.

Interdigital capacitance sensing of moisture content in rubber wood

A low-cost, repeatability, and linearity interdigital capacitive transducer is proposed with an explanation of experimental results. The probe is in the form of a printed circuit board (PCB) with configuration of two interpenetrating comb electrodes, which is different from the configuration of the moisture content sensors available in the market and literature. The moisture contents of the tested rubber wood samples were in the range of 6–70%. The change in capacitance of sensing probe due to the change of moisture content inside rubber wood was detected by the modified bridge circuit. The performance of this sensor is 2% accuracy error with 0.98% precision error.

Moisture content measurement in paddy

Moisture content is an important quantity for agriculture product, especially in paddy. In principle, the moisture content can be measured by a gravimetric method which is a direct method. However, the gravimetric method is time-consuming. There are indirect methods such as resistance and capacitance methods. In this work, we developed an indirect method based on a 555 integrated circuit timer. The moisture content sensor was capacitive parallel plates using the dielectric constant property of the moisture. The instrument generated the output frequency that depended on the capacitance of the sensor. We fitted a linear relation between periods and moisture contents. The measurement results have a standard uncertainty of 1.23 % of the moisture content in the range of 14 % to 20 %.

A Wireless Hay Bale Status Sensor Suite Using PCB Sensor Technology

The spontaneous combustion of curing hay bales poses serious safety and financial issues to farmers and ranchers across the United States and abroad. The primary cause of this spontaneous combustion is the baling of hay before it has adequately dried and reached a sufficiently low moisture content level. This inadequate drying is primarily due to the farmer allowing the hay to dry in the field after cutting for a given period of time. But unfortunately, this does not always ensure that the hay has sufficiently dried before baling. Spontaneous combustion of hay bales is due to a proliferation of thermophilic bacteria that thrive in a moist and hot environment. If the moisture content of hay is greater than 20%, it provides a suitable environment for mesophilic bacteria, which can heat the hay to as a high as 140°F. Although this is not problematic in and of itself, a 140°F hay bale is a suitable environment for the proliferation of thermophilic bacteria, which can further heat the hay to 170oF. At this temperature, the hay can spontaneous combust, destroying the hay and risking the loss of buildings, equipment, livestock and agricultural workers. To combat this problem, a low-cost, low-power, wireless hay bale status sensor suite has been developed so that the farmer can easily and safely monitor the conditions inside a curing hay bale, to give the farmer time to take action before the bale spontaneously combusts. The battery operated sensor suite has two sensors in contact with the hay inside the bale, a printed circuit board (PCB) moisture content sensor and a discrete temperature sensor. The extremely low-cost of the PCB moisture content sensor is what enables the practicality of the sensor suite. WiFi is used to transmit moisture content and temperature data to the farmer's smartphone when it comes within range. The sensor suite is placed inside the bale at the time of baling. After the bale has fully cured, in four to six weeks, the reusable sensor suite can be removed and used in a new bale.

Advanced Wireless Sensor Nodes - MSFC

IMAPS Device Packaging Conference 2017 Engineered Micro Systems & Devices Track Advanced Wireless Sensor Nodes - MSFC Abstract Kosta Varnavas NASA / Marshall Space Flight Center NASA field center Marshall Space Flight Center (Huntsville, AL), has invested in advanced wireless sensor technology development. Developments for a wireless microcontroller back-end were primarily focused on the commercial Synapse Wireless family of devices. These devices have many useful features for NASA applications, good characteristics and the ability to be programmed Over-The-Air (OTA). The effort has focused on two widely used sensor types, mechanical strain gauges and thermal sensors. Mechanical strain gauges are used extensively in NASA structural testing and even on vehicle instrumentation systems. Additionally, thermal monitoring with many types of sensors is extensively used. These thermal sensors include thermocouples of all types, resistive temperature devices (RTDs), diodes and other thermal sensor types. The wireless thermal board will accommodate all of these types of sensor inputs to an analog front end. The analog front end on each of the sensors interfaces to the Synapse wireless microcontroller, based on the Atmel Atmega128 device. Once the analog sensor output data is digitized by the onboard analog to digital converter (A/D), the data is available for analysis, computation or transmission. Various hardware features allow custom embedded software to manage battery power to enhance battery life. This technology development fits nicely into using numerous additional sensor front ends, including some of the low-cost printed circuit board capacitive moisture content sensors currently being developed at Auburn University.

Simultaneous Moisture Content and Mass Flow Measurements in Wood Chip Flows Using Coupled Dielectric and Impact Sensors.

An 8-electrode capacitance tomography (ECT) sensor was built and used to measure moisture content (MC) and mass flow of pine chip flows. The device was capable of directly measuring total water quantity in a sample but was sensitive to both dry matter and moisture, and therefore required a second measurement of mass flow to calculate MC. Two means of calculating the mass flow were used: the first being an impact sensor to measure total mass flow, and the second a volumetric approach based on measuring total area occupied by wood in images generated using the capacitance sensor’s tomographic mode. Tests were made on 109 groups of wood chips ranging in moisture content from 14% to 120% (dry basis) and wet weight of 280 to 1100 g. Sixty groups were randomly selected as a calibration set, and the remaining were used for validation of the sensor’s performance. For the combined capacitance/force transducer system, root mean square errors of prediction (RMSEP) for wet mass flow and moisture content were 13.42% and 16.61%, respectively. RMSEP using the combined volumetric mass flow/capacitance sensor for dry mass flow and moisture content were 22.89% and 24.16%, respectively. Either of the approaches was concluded to be feasible for prediction of moisture content in pine chip flows, but combining the impact and capacitance sensors was easier to implement. In situations where flows could not be impeded, however, the tomographic approach would likely be more useful.

Sensing Technologies for Grain Crop Yield Monitoring Systems: A Review

Purpose: Yield monitoring systems are an essential component of precision agriculture. They indicate the spatial variability of crop yield in fields, and have become an important factor in modern harvesters. The objective of this paper was to review research trends related to yield monitoring sensors for grain crops. Methods: The literature was reviewed for research on the major sensing components of grain yield monitoring systems. These major components included grain flow sensors, moisture content sensors, and cutting width sensors. Sensors were classified by sensing principle and type, and their performance was also reviewed. Results: The main targeted harvesting grain crops were rice, wheat, corn, barley, and grain sorghum. Grain flow sensors were classified into mass flow and volume flow methods. Mass flow sensors were mounted primarily at the clean grain elevator head or under the grain tank, and volume flow sensors were mounted at the head or in the middle of the elevator. Mass flow methods used weighing, force impact, and radiometric approaches, some of which resulted in measurement error levels lower than 5% (R 2 = 0.99). Volume flow methods included paddle wheel type and optical type, and in the best cases produced error levels lower than 3%. Grain moisture content sensing was in many cases achieved using capacitive modules. In some cases, errors were lower than 1%. Cutting width was measured by ultrasonic distance sensors mounted at both sides of the header dividers, and the errors were in some cases lower than 5%. Conclusions: The design and fabrication of an integrated yield monitoring system for a target crop would be affected by the selection of a sensing approach, as well as the layout and mounting of the sensors. For accurate estimation of yield, signal processing and correction measures should be also implemented.

Hydration Monitoring and Moisture Control of Cement-Based Samples Through Embedded Wire-Like Sensing Elements

In this paper, a time-domain reflectrometry (TDR)-based solution for monitoring moisture content in cement-based samples is presented. The proposed system employs a simple flexible biwire, which acts as a distributed sensing element (SE) (as opposed to traditional, local moisture content sensors). Once embedded, the SE remains permanently inside the cement-based sample and can be used both for monitoring the hydration process of the sample structures (ex-ante monitoring) and, successively, for monitoring possible water infiltration during the service life of the structure (ex-post monitoring). In practical applications, the SE could be employed inside building structures at the time of construction, and it could be used for the aforementioned moisture content monitoring purposes. As a preliminary validation of the practical feasibility of the proposed system, in this paper, two cement-based samples (made of mortar and concrete, respectively) were equipped with a SE, and their water content was monitored through TDR measurements, over a 28-day period (thus mimicking the ex-ante monitoring conditions). Furthermore, to verify the potential of the proposed method also for the ex-post monitoring, the air-dried mortar sample was intentionally subjected to wetting conditions and the resulting rising damp was observed through the proposed TDR-based system.

Detection Model for Effect of Soil Salinity and Temperature on FDR Moisture Content Sensors

Detection Model for Effect of Soil Salinity and Temperature on FDR Moisture Content Sensors

A PCB Technology Moisture Content and Electrical Conductivity Sensor Probe for Agricultural and Horticultural Applications

Commercial printed circuit board (PCB) technology affords the realization of low-cost sensor probes for agricultural and horticultural applications. Plant growth can be optimized when the soil (in field crop applications) or the substrate (in greenhouse crop applications) properties can be measured and properly adjusted. Two important parameters are moisture content and electrical conductivity. Measuring moisture content allows the grower to better time irrigation for most efficient crop growth. Accurate moisture content measurement also allows the grower to apply sufficient irrigation volume for optimum plant growth while avoiding excessive irrigation volume. Likewise, measuring the electrical conductivity reveals useful information regarding ions in the soil or substrate, which can be used to optimize the application of plant nutrients or manage soil salinity. Commercial soil probes are expensive, which limits their widespread use in commercial applications. PCB probes, on the other hand, can be very inexpensive and can quickly be redesigned to modify the form factor for different applications. These sensors make use of the materials and processes inherent in commercial PCB manufacturing, including the FR4 substrate, patterned Cu cladding and soldermask. The non-conductive E-glass FR4 substrate is used as the rigid backbone of the sensor probe. The patterned Cu cladding is used for electrodes and signal traces. The polymeric soldermask is used as a thin insulating and moisture barrier layer. With these materials, insulated fringing field sensors can be realized on the surface of the PCB to measure moisture content, while exposed metal pads on the surface can be used to measure electrical conductivity. Additionally, the PCB probe is directly compatible with the integration of any desired integrated electronic components. Furthermore, the turnaround time for a new PCB sensor design can be as little as 24 hours at modest cost, making this technology economically superior to traditional sensor technologies, such as silicon based MEMS, where it can take months to realize a new design and be very expensive. A prototype sensor probe has been designed, fabricated and evaluated. Test data is analyzed, compared with test data from traditional sensor probes and presented.

Small resistive wood moisture sensors: a method for moisture content determination in wood structures

The wood moisture content influences the service life of wood structures since wood is susceptible to decay by rot fungi if it is exposed to high moisture contents during long periods of time. In rain exposed structures, the moisture content close to end grain surfaces and joints can be significantly higher than the average moisture content, but moisture content determinations at such locations require small moisture content sensors. This paper presents small resistive moisture content sensors fastened by electrically conductive adhesive. The relationship between moisture content and electrical resistance was determined for Norway spruce (Picea abies (L.) Karst.) for a wide range of moisture conditions achieved both by equilibrating specimens over saturated salt solutions and by the pressure plate method. The error, i.e. the difference between the gravimetric moisture content and the moisture content from the regression equation, increased with increasing moisture content. Neither the wood type (heartwood/sapwood) nor the growth rate (southern or northern Sweden) influenced the resistance-moisture content relationship.