Kaida Khalid

Application of microwave moisture sensor for determination of oil palm fruit ripeness

Application of Microwave Moisture Sensor for Determination of Oil Palm Fruit Ripeness This paper describes the development of a low cost coaxial moisture sensor for the determination of moisture content (30 % to 80 % wet-weight basis) of the oil palm fruits of various degree of fruit ripeness. The sensor operating between 1 GHz and 5 GHz was fabricated from an inexpensive 4.1 mm outer diameter SMA coaxial stub contact panel which is suitable for single fruit measurement. The measurement system consists of the sensor and a PC-controlled vector network analyzer (VNA). The actual moisture content was determined by standard oven drying method and compared with predicted value of fruit moisture content obtained using the studied sensor. The sensor was used to monitor fruit ripeness based on the measurement of the phase or magnitude of reflection coefficient and the dielectric measurement software was developed to control and acquire data from the VNA using Agilent VEE. This software was used to calculate the complex relative permittivity from the measured reflection coefficient between 1GHz and 5 GHz.

Development of conductor-backed coplanar waveguide moisture sensor for oil palm fruit

The analysis, design and performance of a conductor-backed coplanar waveguide (CBCPW) moisture sensor are described. The sensor can be used to determine the moisture content (MC in per cent) in oil palm fruit and other agricultural products. The sensor consists of three parts - the coupling system representing the transition between the coaxial line and the CBCPW, the two-layer structures of the CBCPW and the sensing area with its semi-infinite three-layer CBCPW structure. A relationship between the scattering parameter or attenuation of the sensor and the moisture content of the sample has been developed. The reflection and transmission phenomena in the sensor structure can be represented by a signal flow graph and can be simplified by the use of non-touching loop rules. The calculation of is based on the quasi-transverse electromagnetic mode approximation. This work also studies the effect of the thickness of the protective layer and the size of the gap between the conducting line and the upper ground plane on the sensitivity and dynamic range of the sensor. Close agreement between the theoretical prediction and experimental results is obtained. The sensitivity and accuracy of the sensors are about and 1% (unit MC, wet basis), respectively. The sensor is suitable for development as a complete instrument and can be used for quality assessments of oil palm fruit and other agricultural products.

Dual frequency microstrip antenna sensor for water content measurements independent of temperature variation

Temperature variation causes errors in all indirect moisture measurement methods. To increase the accuracy of moisture content determination and to reduce the influence of temperature, a two-parameter measurement is used. The method uses the magnitude of reflected waves at two microwave frequencies in the X-band region. A dual frequency sensor system is developed to measure moisture content of dielectric-lossy liquids. The experiment is based on measurements of far-field reflection magnitudes at two different frequencies 8.48 GHz and 10.69 GHz using circular microstrip antennas. A calibration equation is sought that instantly gives temperature-independent moisture content of the samples under consideration. The sensor is integrated with a data acquisition card to record the detected reflection signals. The data analysis and error-correction technique are implemented using custom designed software. The system is tested using diluted rubber latex with moisture content ranging from 39.8% to 91.2% wet basis. The moisture content was predicted with a standard error less than 1.3% for the temperature range of 25 °C to 63 °C compared to the standard oven-drying technique.

Dual-Frequency Microwave Moisture Sensor Based on Circular Microstrip Antenna

A dual-frequency sensor was developed to measure moisture content of lossy liquids. The experiment is based on measurements of far-field reflection at two frequencies in the X-band, 8.48 and 10.69 GHz. The replacement of the conventional open horn antenna with microstrip radiating patches makes the sensor more versatile and compact. The sensor is interfaced to a notebook computer using a multipurpose data acquisition board and few custom made circuits. Data collection, errors correction and calibration modules were written using LabVIEWreg programming language. Three calibration methods were used to obtain an empirical equation, which is applied to obtain the moisture content of the rubber latex samples. Moisture content can be determined with a standard error 0.49%.

Development of Planar Microwave Moisture Sensors for Hevea Rubber Latex and Oil Palm Fruits

A review of the several moisture sensors using planar structures such as microstrip, conductor-backed coplanar waveguide (CBCPW) and microstrip antenna is described. These sensors are used for determination of moisture content in hevea rubber latex and oil palm fruit. This study includes the state of the art of sensor design by which the dielectric constant and dielectric loss of the hevea latex and oil palm are taking into consideration. A prototype developed known as microwave reflection type latexometer is able to measure the moisture content of hevea latex with the accuracy of less than 1% and suitable to be used at latex collecting center and latex dipping industries for process control. A close relationship has been found between insertion loss and moisture content in the mesocarp of oil palm fruit for the CBCPW sensor. This relationship will give the possibility of using this sensor to gauge fruit ripeness or oil content in the mesocarp

Water detection in fuel tanks using the microwave reflection technique

Water is often present in fuel tanks due to night and day temperature changes, resulting in a build-up of condensed water within the inner surface of the tank. The expectancy of water infiltration in fuel tanks is even higher in flooding prone areas. Water settlement at the bottom of the tank causes internal corrosion. In this work, a simple, low cost and accurate microwave reflection type system for detection of water in fuel tanks has been developed. A module consisting of a microwave generator and a detecting diode is used to measure the microwave reflection coefficient at various positions through the fuel tank. In the course of the study, a motion control and data acquisition system has been developed. Software written using the LabVIEW programming language is used to control the movement of the sensor and for the data acquisition. Theoretical and experimental results show the ability of the system to detect the presence of a water level down to approximately 1 mm. A simple theoretical model for power prediction of the reflected signal at various positions of the sensor in the tank is also presented.

Fast and Accurate Technique for Determination of Moisture Content in Oil Palm Fruits using Open-Ended Coaxial Sensor

A simple, fast and accurate technique employing an open-ended coaxial sensor for the determination of the moisture content in oil palm fruit is presented. For this technique, a calibration equation has been developed based on the relationship between the measured moisture content obtained by the oven drying method and the phase of the reflection coefficient of the sensor for 21 fruits. The moisture content predicted by the sensor was in good agreement with that obtained using the standard oven drying method within � 5% accuracy when tested on 145 different fruits samples. (DOI: 10.1143/JJAP.44.5272) Palm oil is now one of the worlds most popular edible oils. It is extracted from the flesh of oil palm fruits by a series of processes performed at a mill. The quality and quantity of the oil are functions of the ripeness of the fruit. Moisture content is one of the most important factors that influence the ripeness of oil palm fruit. 1) The measurement of moisture content using a microwave method is widely known to be accurate and rapid. However, not all microwave techniques are suitable for single fruit measurements due to the small sample size. It has been pointed out that a microstrip sensor 2) offers distinct advantages in this respect since only a small part of the sample interacts with the sensor and there is no restriction on the sample size. Unfortunately, use of the sensor requires laborious sample preparation in which the fresh mesocarp of the oil palm fruit has to be separated from the nut, cut into small pieces and crumbled to form a semi solid sample. In this article, we propose the use of an open-ended coaxial sensor to realize a simple, fast and accurate technique for the determination moisture content in oil palm fruits. In the near future, the sensor shall be incorporated in the development of a cost- effective portable microwave moisture meter operating at frequencies below 5 GHz. The open-ended sensor, as shown in Fig. 1, was fabricated from a 12.7 mm by 12.7 mm square flange, sub-miniature A type (SMA) coaxial stub contact panel. The dielectric material separating the gold-plated, stainless-steel inner and outer conductors of the coaxial line is PTFE. The diameters of the inner and outer conductors are 1.3 and 4.1 mm, respectively. The PTFE stub was machined flat and polished. The reflection coefficient of the oil palm fruits was measured using the sensor with a HP8720B Vector Network Analyzer (VNA). All calibrations and measurements were performed for 801 points in the frequency range between 1 and 5 GHz at room temperature in a stepped continuous-wave (CW) mode for which a synthesized frequency could be obtained for each data point. A full one-port calibration technique was implemented on the BB 0 plane using an HP 85052D 3.5 mm calibration kit. Under the assumption of a quasi-TEM mode, the measured reflection coefficientAA 0 of the fruit sample on the plane AA 0 can be de-embedded to the connector end of the probe which coincides with the calibration plane BB 0 to give a reflection coefficientBB 0 by the relation 3) � BB0 ¼ � AA0 expð jDÞ; ð1Þ whereis the propagation constant of the coaxial line section and D is the physical length of the coaxial line. Sampling was performed on fruits of various degrees of ripeness from twenty bunches from different 12-year-old oil palms of the tenera variety. Part of the fresh mesocarp of each fruit was sliced in the longitudinal direction to ensure good contact between the surface of the mesocarp and the sensor. The nondestructive testing of fruits can be accom- plished in the future by using an open-ended coaxial sensor with inner and outer conductors of small diameter. The true moisture content of the fruit samples was determined using the standard oven drying method. 4) A set of 21 fruits was used to establish the calibration equation relating the true moisture content to the phase of the reflection coefficient. The reliability of the calibration equation was tested using another set of 145 different fruits. Figure 2 clearly shows a linear relationship between the true moisture content (mc) of the oil palm fruits and the phase of the reflection coefficient, � . Due to the large number of frequency points, only representative frequency points, namely 1, 2, 3, 4 and 5 GHz, are shown in the graph. The coefficients A and B along with their R-squared values found using the linear regression model,

Improved Formulation for Admittance of Thin and Short Monopole Driving From Coaxial Line Into Dissipative Media

An improved formulation of the admittance equation for small and thin monopole is presented where the coefficient of the capacitive correction term can be calculated directly from the values of the inner and outer radius of the coaxial line. The results were found to agree well with measurements and the finite element method (FEM). Some rules, features, and limitations of the improved formula are also discussed.

Development and Design of Microstrip Moisture Sensor for Rice Grain

This paper deals with the analysis and design of a microstrip sensor for accurate determination of moisture content (MC) in rice grains. The sensor consists of four layers- RT-Duroid substrate, protective layer, wet medium as a sensing area, and air. A functional relationship has been developed between microwave attenuation of the sensor and moisture content in grains for four layered semi-infinite microstrip structure, and close agreement has been found between computed and experimental results. The analysis of electromagnetic wave propagation in the sensor structure is simply represented and prediction of dielectric properties of rice grains is given by a dielectric mixture model. This work also studies the effect of thicknesses of protective layer on the sensitivity of the sensor. The sensor is suitable for development as a complete instrument and to estimate the optimum moisture content of rice grains, more quickly and accurately

The Analysis of Multi-Layer Conductor-Backed Coplanar Waveguide for Moisture Sensor Application

The analysis of conductor-backed coplanar waveguide moisture sensor by using numerical method is described. The effective dielectric constant, characteristic impedance and dielectric loss of this multi-layer structure are calculated at various moisture contents with respect to protective layer thickness. The analysis shows that calculated values are drastically affected by a small thickness of the protective layer. The experimental results of the attenuation of sensor at various moisture contents agree reasonably with the theoretical data based on the above analysis. The information available from this study is important for estimating of the dynamic range and optimal design of the sensor.The analysis of conductor-backed coplanar waveguide moisture sensor by using numerical method is described. The effective dielectric constant, characteristic impedance and dielectric loss of this multi-layer structure are calculated at various moisture contents with respect to protective layer thickness. The analysis shows that calculated values are drastically affected by a small thickness of the protective layer. The experimental results of the attenuation of sensor at various moisture contents agree reasonably with the theoretical data based on the above analysis. The information available from this study is important for estimating of the dynamic range and optimal design of the sensor.