Microwave Moisture Meter Research Articles

Convolutional neural network-based multimodal image information fusion for moisture damage assessment of cultural heritage buildings

Water is an essential factor causing the deterioration of historical and cultural heritage, and identifying and quantifying moisture damage is essential for conserving cultural heritage buildings. This study combines infrared thermography (IRT) and microwave technology to investigate moisture-induced diseases and the variation of the spatial distribution of water content in the Yungang Grottoes of China, a World Heritage Site. Information on building humidity distribution was extracted and combined from IRT and microwave information. Furthermore, multi-feature image fusion combines different types of monitoring information through the Convolutional Neural Network (CNN), which is used to diagnose moisture distribution and content accurately. The features obtained from different non-destructive methods were then jointly analyzed using statistical analysis methods such as absolute contrast, noise ratio (SNR), and spatial stability to quantify the artifact moisture defect data, thus improving the accuracy and range of features for detecting water-damaged pathologies. The results show that the combination of IRT and microwave information technology not only qualitatively but also quantitatively analyses the moisture in the building, significantly using microwave moisture meters to study water distribution at different depths and surface characterization by IRT. The use of non-destructive monitoring tools helps to guide the diagnosis of moisture damage, restoration of heritage buildings, and the planning of intervention strategies.

MICROWAVE MOISTURE MEASUREMENT

The article describes the wide possibilities of microwave methods for measuring humidity of a large range of products, their differences and advantages. Specific examples and the most common schemes of implemented microwave moisture meters are given. The ways of development of microwave moisture measurement in modern conditions are shown.

Microwave Moisture Meter for Cereal Grains

A method and instrument for measurements of the moisture content of cereal grains on the basis of a microwave amplitude method are developed. Results of studies of the metrological characteristics of an experimental prototype are presented. Problems for further study focused on reducing the error components of microwave moisture meters are defined.

Microwave moisture meter for in-shell peanut kernels

A microwave moisture meter built with off-the-shelf components was developed, calibrated and tested in the laboratory and in the field for nondestructive and instantaneous in-shell peanut kernel moisture content determination from dielectric properties measurements on unshelled peanut pod samples. The meter operates at a single frequency of 5.8 GHz and uses free-space transmission measurement principles for determining the dielectric properties of the peanut pods. From these properties, a dielectric-based algorithm provides peanut kernel moisture content from measurements on pods. Field tests at a peanut buying station showed that moisture content of peanut kernels can be determined with a standard error of performance of 0.82% when compared to the official moisture meter which required the pods to be shelled before kernel moisture content can be determined. When performance of both the microwave moisture meter and the official meter were compared to the oven-drying standard method, values of the standard errors of performance were 0.53% for the microwave moisture meter and 0.87% for the official moisture meter.

A microwave sensor for the characterization of bovine milk

The use of a moisture sensor, based on microwave absorption at 40 GHz, is explored for the direct determination of the water content in milk. The operating principle of the device is based on the relative decrement of a transmitted signal through the sample. The results of the study are based on the measurements of over 150 samples of milk, taken from individual cows, from bulk tank milk and from skimmed milk sources. A high correlation is revealed between the signal absorption, measured by the sensor, and the nominal main solids content in bovine milk, determined independently. In addition, the fat concentrations in raw milk, considered separately from the other constituents, were also well correlated to the microwave moisture meter readings. As the other solid fractions of milk show less or non-significant correlation to the absorption coefficient, it is concluded that the correlation of fat to signal decrement is due to an excluded volume effect.

Assessment of Real-Time, In-Shell Kernel Moisture Content Monitoring with a Microwave Moisture Meter during Peanut Drying

Abstract. The present-day peanut drying process lacks the capability of in-situ kernel moisture content determination in real-time. Samples of peanut pods have to be taken from the drying trailer, cleaned and shelled by an operator to test for the kernel moisture content. The frequency with which the operator samples the peanuts in the drying trailer to determine kernel moisture content determines the accuracy of the drying process in reaching the targeted kernel moisture content. However, by using a microwave moisture meter, developed within USDA ARS and operating at power levels of a few milliwatts, the moisture content of the peanut kernel can be determined without having to shell the peanut pods. An automated quarter-scale drying system, equipped with the microwave meter, was developed and tested, and it has demonstrated effective control of the drying process and accurate real-time monitoring of kernel moisture content. The objective of this study was to evaluate the performance of the drying system with varying initial kernel moisture contents and atmospheric conditions. Therefore, three trials were run where such conditions were varied. Analysis of variance was performed, and standard errors of prediction were evaluated to compare the kernel moisture content values predicted by the microwave moisture meter to those determined by the oven method. In-shell kernel moisture content was determined in real-time with a standard error of performance ≤ 0.55% moisture when compared to the reference oven-drying method. Overall evaluation demonstrated that the automated drying system is an effective solution for user-independent dryer control and real-time, in-shell kernel moisture content monitoring.

Research on Controlled Permeability Formwork of Nonwoven Fabrics to Retain the Humidity on the Concrete Surface

It is of great significance for concrete to be cured using controlled permeability formwork of nonwoven fabrics especially in dry area. CPF can improve durability of concrete through decreasing the ratio of water and cement in concrete surface. CPF could also retain the water within it. The role of concrete curing using CPF or not is test by MOIST200B type microwave moisture meter. In addition, the permeability of concrete surface between the concrete which use CPF or not is analyzed through the air permeability test, the initial surface absorption of concrete test (ISAT). The testing results indicate that there is little effect on curing of concrete using controlled permeability formwork liner.

An Automated Approach to Peanut Drying with Real-Time Microwave Monitoring of In-Shell Kernel Moisture Content

<abstract><title><italic>Abstract. </italic></title> Peanut (arachis hypogaea L.) drying is an essential task preceding the grading process. Kernel moisture is one of five parameters used to establish the grade for a specific lot of peanuts, and it is imperative that peanuts be dried to a kernel moisture content <10.5% wet basis for grading and storage purposes. Today’s peanut drying processes utilize decision support software based on modeling and require substantial human interaction to obtain kernel moisture content. These conditions increase the likelihood of peanuts being overdried or underdried. This research addresses the need for an automated controller with real-time, in-shell kernel moisture content determination capabilities. By using a microwave moisture meter, developed within United States Department of Agriculture, Agricultural Research Service, the moisture content of the peanut kernel can be determined without having to shell the peanut pods. The kernel moisture content and atmospheric conditions serve as inputs to the controller, and thus, air temperature and drying time are controlled automatically. Such implementation reduces overdrying and underdrying, preserves quality of peanuts, and minimizes energy consumption through efficient control of the heater. In this article, a quarter-scale drying system with automated control is discussed. Kernel moisture content was determined in real time with a standard error of performance of 0.55% moisture when compared to the reference oven-drying method. Such results show promise for large-scale implementation and testing.

Predicting oven-dry density of Sugi (Cryptomeria japonica) using near infrared (NIR) spectroscopy and its effect on performance of wood moisture meter

We propose a non-destructive method to predict the oven-dry density of Sugi (Cryptomeria japonica D. Don) using near infrared (NIR) spectroscopy so as to calibrate a commercial moisture meter. A prediction model for oven-dry density was developed using NIR spectra obtained from Sugi samples with a known density. The density of air-dried Sugi boards was predicted with the developed model. Then, the moisture content (MC) of the boards was measured by a hand-held capacitance-type and an in-line microwave moisture meters. For each board, the moisture meters were calibrated by the predicted density. The predicted density was correlated with the measured one with an R2 of 0.81 and a standard error of prediction (SEP) of 15.3 kg/m3 within the measured density of 279.2–436.4 kg/m3, indicating that the developed model was applicable for predicting oven-dry density of Sugi. The MC readings of both moisture meters showed a good correlation with the oven-dry MC that ranged from 12.1 to 28.9 %. For both moisture meters, the density calibration with the NIR-predicted density gave a higher R2 and a lower SEP than with the conventional calibration with the mean density. These results demonstrate that the present density calibration using NIR spectroscopy could improve the performance of the moisture meters for the air-dried Sugi boards with varying densities.

Integrating an Embedded System in a Microwave Moisture Meter

The conversion of a PC- or laptop-controlled microwave moisture meter to a stand-alone meter hosting its own embedded system is discussed. The moisture meter measures the attenuation and phase shift of low power microwaves traversing the sample, from which the dielectric properties are calculated. The power level of the microwaves is similar to that of Wi-Fi. Therefore, the sample is unharmed and no heating occurs. The dielectric properties are then used for rapid, nondestructive determination of the moisture content in the grain or seed sample. The initial system consisted of the moisture meter, controlled via USB interface by an external laptop or PC. Though effective, the system lacked full portability and was susceptible to computer crashes and interruptions in communication between the meter and laptop. To improve the system, a microcontroller was selected in the design of an embedded system for the moisture meter. The microcontroller provides a graphical 144 x 32 pixel LCD and 16-button keypad to facilitate user interaction. The embedded system provides the following functionalities: user interface (input/output), event execution, process control, data acquisition and data storage. Testing showed that the moisture meter with the new embedded system maintained the performance and accuracy observed for the original meter with PC or laptop control. Results are included to show the similarity of measurements taken with the microwave meter (both versions) to measurements taken with a vector network analyzer. The integration of the embedded system with the microwave moisture meter provides a cost-effective, portable, and robust solution for microwave moisture sensing.

Automatic control of moisture in agricultural products by methods of microwave aquametry

This paper describes the results of the elaboration of the microwave moisture meter for continuous control of moisture of grain, sugar and dry milk in the technological processes of their production. Dielectric properties of these materials and high technological requirements on the accuracy determine the choice of investigation methods. Unlike the known microwave moisture meters, used in the case of grain for the flour-milling industry, we offer a two-sensor device using two algorithms with the second algorithm taking into account the influence of the refraction factor of the electromagnetic energy in the surface layer of the freshly moistened grain. The increase in the accuracy of moisture control in the production of sugar and dry milk is obtained at the expense of the influence of the material density placed into the volume resonator. In this case two parameters of the electromagnetic wave in the resonator are controlled. These parameters are connected with material moisture and density.

SIMPLE INSTRUMENT FOR MOISTURE MEASUREMENT IN GRAIN BY FREE-SPACE MICROWAVE TRANSMISSION

A simple microwave moisture meter for grain was introduced with reduction of the size and volume of theinstrument by means of 22 microstrip patch array antennas. The attenuation and phase shift produced by Korean short-grainrough rice, brown rice, and barley were analyzed to estimate the relationships between moisture density in the grain and theattenuation and phase shift. Second- and third-order polynomial attenuation models were a better measure of moisture densitythan were phase shift models. A grain moisture meter using microwave attenuation in free-space was constructed. A prototypegrain moisture meter consisting of a 10.5 GHz oscillator, patch array antennas, isolator, detector, and digital voltmeterprovided a coefficient of determination, standard error of prediction (SEP), and bias of 0.975, 0.62% moisture content, and-0.05% moisture content, respectively.

Method to estimate the internal stresses due to moisture in wood using transmission properties of microwaves

The purpose of this paper is to offer a new method for detecting stress in wood due to moisture along the lines of a theory reported previously. According to the theory, the stress in wood could be estimated from the moisture content of the wood and the power voltage of a microwave moisture meter (i.e., attenuation of the projected microwave). This seems to suggest a possibility of utilizing microwaves in the field of stress detection. To develop such an idea, the stress formulas were initially modified to the form of an uni-variable function of power voltage, and the application method of the formulas to detection was tried. Finally, these results were applied to the data of sugi (Cryptomeria japonica) lumber in the previous experiment. The estimated strains showed fairly good agreement with those observed. It could be concluded from this study that the proposed method might be available for detecting stress in wood due to moisture.

Density-Independent Moisture Measurement Using Dielectric Constants at Two Microwave Frecquencies

It is important to find a method using the dielectric properties of the material to determine moisture content independent of the density in developing microwave moisture meter. Moisture measurement based on the dielectric properties of the material can be applied in various microwave techniques. In this paper, a new method using dielectric constants only for density-independent moisture determination is proposed. The new method was used to measure moisture content of green tea, and the results are presented. It was shown that the Root Mean Square Error (RMSE) is 2.4% in the moisture measurement for the samples in 8-49% moisture range and 0.14-0.69 g/cm3 density range. The comparison of the proposed method with the former method on green tea was also presented. The results show that the accuracy of moisture determination by the proposed method is better than the former method.

ADVANCES IN SENSING GRAIN MOISTURE CONTENT BY MICROWAVE MEASUREMENTS

The history of information development on the electrical properties of grain and their use for sensing moisture content is briefly reviewed. Basic principles of grain moisture sensing by microwave measurements are presented, including techniques for moisture content determination independent of bulk density. Recent research findings on densityindependent microwave determination of moisture content in grain are briefly summarized. Three functions of the grain dielectric properties or the wave parameters are identified from which moisture content can be determined independent of bulk density, and the performance of these density-independent functions is compared for sensing moisture content in hard red winter wheat. Results show that standard errors of performance of about 0.3% moisture content or less can be achieved by using these functions with microwave measurements at frequencies between 11 and 18 GHz. Results of these and other cited studies indicate that measurement techniques for density-independent moisture sensing in grain should provide a sound basis for development of microwave moisture meters for on-line applications.

Development of Microwave Moisture Meter for Free-Flowing Materials

Development of Microwave Moisture Meter for Free-Flowing Materials

Some Aspects of the Optimal Control of the Coal Separation Process

A knowledge of changes in quality characteristics of a raw coal feed to a preparation plant is essential for designing of its washing technology and optimum control of the washing processes in order to reduce coal losses. The long-term industrial experiments performed in a group of coal preparation plants, included the measurements of washability curves, ash content, moisture content and calorific value of power small coal. Automatic measurement systems including radiometric ash monitors, microwave moisture meters and calorific value calculators have been applied.The time-variability of washability curves has been estimated on the base of laboratory-analysed coal samples. A statistical analysis of the above parameters has been done. This analysis allows to introduce the short-term prediction methods of coal quality changes. On an example of a coal preparation plant the analysis of washing parameters basing on a computerized simulation model, is presented. Basing on the results of such calculations the optimum control strategy can be evaluated

A density-independent microwave moisture meter for heterogeneous foodstuffs

Experiments on unground fish meal have been performed using a prototype microwave moisture meter: This device, which was claimed to be density-independent for loose materials such as fibres and powders, measures two microwave parameters simultaneously. A full examination of its performance over a wide range of density and moisture content whilst not entirely justifying this claim shows that it is considerably better than any instrument based on single parameter measurement. For very heterogeneous materials the moisture content could be determined to within ±0·6% moisture content or better-depending on the range of density variation experienced in practice.

High-Moisture Content Measurement of Grain by Microwaves

AbstractHigh-moisture content of grain (rice, corn, soybean, and red bean) can be measured by the microwave moisture meter reported in this paper. The measurement results are obtained by improving the construction of the microwave moisture meter for high-moisture grain and by using the new method of considering both the microwave attenuation and the density of the grain sample. The measured maximum moisture content is 52% within the error of about ±0.6% on a wet basis for red bean.

Compact Microstrip Sensor For High Moisture Content Materials

A compact form of stripline sensor has been developed which is robust in construction and suitable for measuring moisture contents up to 100% (wet basis). It offers potential for further miniaturisation of microwave moisture meter circuitry.