FREE-SPACE MICROWAVE MEASUREMENT of LOW MOISTURE CONTENT IN POWDERED FOODS

2000 ◽  
Vol 24 (1) ◽  
pp. 39-56 ◽  
Author(s):  
RAM M. NARAYANAN ◽  
KHOI T. VU
Keyword(s):  
Moisture Content ◽  
Free Space ◽  
Microwave Measurement

Microwave Non-Destructive Testing of Coatings and Paints Using Free Space Microwave Measurement

2005 ◽  
Vol 2 (2) ◽  
pp. 17
Author(s):  
Norhayati Hamzah ◽  
Deepak Kumar Ghodgaonkar ◽  
Kamal Faizin Che Kasim ◽  
Zaiki Awang
Keyword(s):  
Free Space ◽  
Protective Coatings ◽  
Microwave Measurement ◽  
Multiple Reflections ◽  
Destructive Testing ◽  
Lens Antennas ◽  
Coatings And Paints ◽  
Microwave Nondestructive Testing ◽  
Mode Transitions ◽  
Diffraction Effects

Microwave nondestructive testing (MNDT) techniques are applied to evaluate quality of anti-corrosive protective coatings and paints on metal surfaces. A tree-space microwave measurement (FSMM) system is used for MNDT of protective coatings. The FSMM system consists of transmit and receive spot-focusing horn lens antennas, a vector network analyzer, mode transitions and a computer. Diffraction effects at the edges of the sample are minimized by using spot-focusing horn lens antennas. Errors due to multiple reflections between antennas are corrected by using free-space LRL (line, reflect, line) calibration technique. We have measured complex reflection coefficient of polyurethane based paint which is coated on brass plates.

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.

Density-independent Microwave Measurement of Moisture Content in Static and Flowing Grain

1993 ◽  
Vol 36 (3) ◽  
pp. 827-835 ◽  
Author(s):  
B. D. McLendon ◽  
B. G. Branch ◽  
S. A. Thompson ◽  
A. Kraszewski ◽  
S. O. Nelson
Keyword(s):  
Moisture Content ◽  
Microwave Measurement

Measurement on the Dielectric Constant of Grass with Rectangular Waveguide at C Band

2011 ◽  
Vol 130-134 ◽  
pp. 2138-2142 ◽  
Author(s):  
Chun Lin Xian ◽  
Yan Chen ◽  
Ling Tong ◽  
Ming Quan Jia
Keyword(s):  
Dielectric Constant ◽  
Measurement Error ◽  
Moisture Content ◽  
Measurement System ◽  
Rectangular Waveguide ◽  
Microwave Measurement ◽  
Error Range ◽  
Constant Measurement ◽  
Standard Block ◽  
Dielectric Constant Measurement

This paper was developed by microwave measurement on the vegetation dielectric constant through using the rectangular-waveguide at C Band. The measurement system and the method of the measurement will be introduced in detail. We have a standard block of known dielectric constant measurement, and then evaluate the error range. The system of measurement error range is ± 5%.At last, the result of this experiment showed that different density corresponds to different dielectric constant in the case of certain moisture content, and the dielectric constant increases with the density.

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.

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