Determination of moisture content in mortar at near relaxation frequency 17 GHz

The knowledge of moisture content in cement based material is important especially for the safety in field work. In this paper, a non-destructive and contactless free space method is used for measurement of moisture content in cement based materials (mortar) at microwave frequencies. The measurement system consists of a 17 GHz dielectric resonator oscillator (DRO) as a microwave source, a Power Meter as the detector, and a pair of lens horn antennas to transmit and receive the microwave signal. An empirical formula of moisture content was obtained by using a relationship between attenuation and moisture content. This model is best for prediction of moisture content greater than 2% with percentage mean error of 3%

A simple rectangular microstrip technique for determination of moisture content in Hevea rubber latex

A simple rectangular microstrip sensor for determination of moisture content in Hevea Rubber Latex is presented in this paper. The microstrip patch sensor was designed to operate at microwave frequency range from 1 to 5 GHz on a RT/Duroid substrate with 6.15 ±0.015 permittivity and 1.27 mm thickness. The width and length of the rectangular patch antenna was 18 mm and 38 mm, respectively. The reflection coefficient of the sensor loaded with Hevea latex at various percentages of moisture content from approximately 36.1% to 88.6 %. Calibration equations have been established between moisture content and phase of reflection coefficient at several selected frequencies. These equations were used to predict the amount of moisture content on Hevea latex based on the measured reflection coefficient values. The actual values of moisture content were obtained using standard oven drying method. The lowest mean relative error between actual and predicted moisture contents was 0.04 at 1 GHz

Variations of reflectance with moisture content in single maize kernels and spinach leaves at wavelength 300 nm to 800 nm

This research describes an optical fiber reflectance technique in determining the moisture content in single maize kernels and spinach leaves in wavelength region from 300 nm to 800 nm. The technique is a simple, fast, non-destructive and accurate way to establish the relationship between reflectance and moisture content of both samples. Spectral acquisitions were controlled using the Ocean Optic Spectra Suite operating software. Samples were illuminated by a light source that combines deuterium and tungsten halogen light sources in a single optical path. The Ocean Optic Spectroscopy system consists of an integrated set of seven 440 μm diameter fibers with six illumination fibers encircling one detection fiber. Spectral changes were related to changes in the apparent colour of maize kernels and spinach leaves as it was influenced by moisture content. The results suggest that the percentage of reflectance decreases with moisture content for both maize kernel and spinach leaves at all wavelengths. Lower values in moisture content will result in a slightly darker colour of both samples which in turn will reduce the percentage values of reflectance. In this work, the actual moisture content was found by applying standard oven drying method whilst the Kubelka-Munk theory was used to characterize the scattering and absorption coefficients of single maize kernels and spinach leaves. The performance characteristics of the optical fiber technique for the determination of moisture content were presented in terms of accuracy, standard deviation, probability density function and tolerance. The relative error of the optical fiber technique to determine moisture content based on reflectance measurements were found to be as low as 0.037 at 590 nm for single maize kernels and 0.073 at 380 nm for spinach leaves