Moisture Content Estimation of Wet Sand from Free-Space Microwave Techniques

2015 ◽  
pp. 277-297
Author(s):  
S. Richards ◽  
A. Tan ◽  
I. Platt ◽  
I. Woodhead
Keyword(s):  
Moisture Content ◽  
Free Space ◽  
Microwave Techniques

Microwave Nondestructive Sensing of Moisture Content and Water Activity of Almonds

2021 ◽  
Vol 64 (4) ◽  
pp. 1373-1379
Author(s):  
Samir Trabelsi
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Bulk Density ◽  
Water Activity ◽  
Free Space ◽  
Loss Factor ◽  
Dielectric Loss Factor ◽  
List Type

HighlightsMoisture and water activity were determined nondestructively and in real time from measurement of dielectric properties.Moisture and water activity calibration equations were established in terms of the dielectric properties.Situations in which bulk density was known or unknown were considered.SEC ranged from 0.41% to 0.68% for moisture and from 0.02 to 0.04 for water activity.Abstract. A method for rapid and nondestructive determination of moisture content and water activity of granular and particulate materials was developed. The method relies on measurement of the dielectric constant and dielectric loss factor at a single microwave frequency. For the purpose of illustration, the method was applied to predicting the moisture content and water activity of almond kernels. A free-space transmission technique was used for accurate measurement of the dielectric properties. Samples of Bute Padre almond kernels with moisture content ranging from 4.8% to 16.5%, wet basis (w.b.), and water activity ranging from 0.50 to 0.93 were loaded into a Styrofoam sample holder and placed between two horn-lens antennas connected to a vector network analyzer. The dielectric properties were calculated from measurement of the attenuation and phase shift at 8 GHz and 25°C. The dielectric properties increased linearly with moisture content, while they showed an exponential increase with water activity. Situations in which the bulk density was known and unknown were considered. Linear and exponential growth regressions provided equations correlating the dielectric properties with moisture content and water activity with coefficients of determination (r2) higher than 0.96. Analytical expressions of moisture content and water activity in terms of the dielectric properties measured at 8 GHz and 25°C are provided. The standard error of calibration (SEC) was calculated for each calibration equation. Results show that moisture content can be predicted with SECs ranging from 0.41% to 0.68% (w.b.) and water activity with SECs ranging from 0.02 to 0.04 for almond kernel samples with water activity ranging from 0.5 to 0.9 and moisture contents ranging from 4.8% to 16.5% (w.b.). Keywords: Bulk density, Dielectric constant, Dielectric loss factor, Free-space measurements, Loss tangent, Microwave frequencies, Moisture content, Water activity.

Measurement of Moisture Content in Powdered Food Using Microwave Free-Space Transmission Technique

2006 ◽  
Vol 321-323 ◽  
pp. 1196-1200 ◽  
Author(s):  
Ki Bok Kim ◽  
Seon Gun Park ◽  
Ji Yeon Kim ◽  
Jong Heon Kim ◽  
Chan Joo Lee ◽  
...  
Keyword(s):  
Phase Shift ◽  
Moisture Content ◽  
Free Space ◽  
Milk Powder ◽  
Correlation Coefficients ◽  
Food Samples ◽  
Coefficient Of Determination ◽  
Powdered Food ◽  
Transmission Technique ◽  
Moisture Content Measurement

In this study, microwave free-space transmission technique was applied to measure the moisture content of powdered food (wheat flour, milk powder, and coffee powder). In frequency range from 1 to 15 GHz, the microwave attenuation and phase shift due to moisture content of food samples were measured and analyzed using vector network analyzer, double rigid horn antennas, and sample holder filled with moist food samples. To estimate the relationship between moisture density of powdered food and the attenuation and phase shift, correlation analysis was performed. The correlation coefficients at each food sample were greater than 0.91. The calibration equation for moisture content measurement having attenuation and phase shift as independent variables at 15 GHz was developed and evaluated. The coefficient of determination and root mean square for all food samples were 0.974 and 0.328 % respectively.

Performance Comparison of Three Density-Independent Calibration Functions for Microwave Moisture Sensing in Unshelled Peanuts during Drying

2020 ◽  
Vol 36 (5) ◽  
pp. 667-672
Author(s):  
Micah A. Lewis ◽  
Samir Trabelsi
Keyword(s):  
Moisture Content ◽  
Real Time ◽  
Complex Permittivity ◽  
Free Space ◽  
Calibration Function ◽  
Moisture Sensor ◽  
Content Determination ◽  
Transmission Measurements ◽  
Independent Calibration ◽  
Moisture Content Determination

HighlightsReal-time, free-space transmission measurements of relative complex permittivity in unshelled peanuts during dryingDynamic application: temperature, density and moisture content changing during dryingThree density-independent calibration functions evaluated for accuracy in real-time moisture content determinationReal-time moisture content determination with standard error of performance (SEP) = 0.55% moisture content for all calibration functionsCalibration function most commonly used with microwave moisture sensor was determined to be most accurate; SEP = 0.448% moisture contentAbstract. A microwave moisture sensor, developed within USDA ARS, has been used to determine moisture content in unshelled peanuts during drying. Relative complex permittivities of the peanuts obtained from free-space transmission measurements at 5.8 GHz are used for the moisture determination. Due to variations in density caused by drying, it is advantageous to estimate moisture content independent of bulk density. Therefore, moisture content was estimated with three density-independent calibration functions to assess which one provided optimal accuracy. One of the functions is based on the measured attenuation and phase shift, and the other two are permittivity based (one of which is commonly used with the microwave moisture sensor). The sensor was calibrated for peanut pod moisture content determination over a temperature range of 10°C to 40°C and a moisture content range of 6.5% to 19% wet basis (w.b.). Statistical analysis showed high coefficients of determination (r2), = 0.97 for the calibration with each function. Peanut pod moisture content was determined with the sensor in real-time as peanuts dried, and estimated moisture content was compared to the reference oven drying method. While the standard error of performance (SEP) for the three functions was = 0.55% moisture content, the calibration function most commonly used with the microwave sensor was observed to be the most accurate (SEP = 0.448% moisture content). Microwave sensing is a viable solution for nondestructive, real-time determination of moisture content in peanuts in dynamic situations such as drying. Keywords: Complex permittivity, Dielectric properties, Free-space measurements, Microwave sensing, Moisture content, Peanut drying.

Determination of Plasma Properties by Free‐Space Microwave Techniques

1962 ◽  
Vol 33 (7) ◽  
pp. 2275-2282 ◽  
Author(s):  
R. Buser ◽  
W. Buser
Keyword(s):  
Free Space ◽  
Plasma Properties ◽  
Microwave Techniques

Contactless Detection of Moisture Content in Blended Fabrics With a Free-Space Microwave Method

2020 ◽  
Vol 69 (5) ◽  
pp. 2139-2144
Author(s):  
Zhong Xiang ◽  
Jinbo Wu ◽  
Chong Qi ◽  
Xudong Hu
Keyword(s):  
Moisture Content ◽  
Free Space ◽  
Microwave Method

Measurement of Moisture Content in Powdered Food Using Microwave Free-Space Transmission Technique

2006 ◽  
pp. 1196-1200
Author(s):  
Ki Bok Kim ◽  
Seon Gun Park ◽  
Ji Yeon Kim ◽  
Jong Heon Kim ◽  
Chan Joo Lee ◽  
...  
Keyword(s):  
Moisture Content ◽  
Free Space ◽  
Powdered Food ◽  
Transmission Technique
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