New density-independent moisture measurement methods using frequency-swept microwave transmission

Microwave nondestructive sensing of moisture content in shelled peanuts independent of bulk density and with temperature compensation

“…However, density measurement is more troublesome and requires a separate measuring system which complicates the moisture meter and increases its price. Therefore, more research efforts were dedicated to developing methods for simultaneous bulk density and moisture determination from dielectric properties or related electrical parameters measurement [31][32][33] or identifying density independent functions and algorithms for moisture determination independent of the bulk density of the material [10,12,14,15,[17][18][19][20][21]. In this paper, three density-independent functions are used to determine moisture content from measurement of attenuation, phase shift, and dielectric properties at microwave frequencies.…”

“…At higher frequencies of several GHz, the ionic conduction effect vanishes, and it is possible to eliminate the effect of bulk density and compensate for temperature effects [9]. Because bulk density measurement is more troublesome and often requires additional measurement instrumentation, several density-independent algorithms [10][11][12][13][14][15][16][17][18][19][20][21] for moisture determination from microwave measurements were developed and effectively tested for moisture sensing in granular and particulate materials. In this paper, three density-independent calibration functions [10,12,15] were used to predict moisture content in shelled peanuts from free-space measurements of attenuation, phase shift, and the dielectric properties at 10 GHz at temperatures ranging from 1 to 38°C.…”

Technology and Signal Processing of Dielectrometric Microwave Sensors for Industrial Applications

“…If the moisture content w increases beyond a certain threshold, the measurement may lose sensitivity. This can be the case when b 0 becomes small as compared with the rest of the sum term in the denominator [3,4]. In general, the functional behavior depends on the coefficients a k and b k , and the moisture content can be calculated from…”

A Low-Cost Microwave Moisture Sensor

“…Also, recent scientific findings provide a basis for solving the problems previously cited. New density-independent calibration functions have been proposed [4,5] that allow moisture content to be determined from microwave measurements without knowledge of density. A method was proposed for simultaneous and independent determination of moisture content and bulk density from measurement of the complex permittivity at microwave frequencies [6,7].…”