Zulkifly Abbas

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.

Complex permittivity measurements at Ka-Band using rectangular dielectric waveguide

The rectangular dielectric waveguide (RDWG) technique has been developed for the determination of the dielectric constant of materials from effective refractive index measurements in the Q and W bands. This paper describes the use of an optimization method in conjunction with the RDWG technique for the determination of both the dielectric constant and loss tangent of materials at Ka-Band. The effect of the uncertainty in the measured sample thickness is presented.

Determination of moisture content in oil palm fruits using a five-port reflectometer.

This paper presents the development of a PC-based microwave five-port reflectometer for the determination of moisture content in oil palm fruits. The reflectometer was designed to measure both the magnitude and phase of the reflection coefficient of any passive microwave device. The stand-alone reflectometer consists of a PC, a microwave source, diode detectors and an analog to digital converter. All the measurement and data acquisition were done using Agilent VEE graphical programming software. The relectometer can be used with any reflection based microwave sensor. In this work, the application of the reflectometer as a useful instrument to determine the moisture content in oil palm fruits using monopole and coaxial sensors was demonstrated. Calibration equations between reflection coefficients and moisture content have been established for both sensors. The equation based on phase measurement of monopole sensor was found to be accurate within 5% in predicting moisture content in the fruits when compared to the conventional oven drying method.

Parallel solution of high speed low order FDTD on 2D free space wave propagation

Finite Difference Time-Domain (FDTD) is one of the most widely used numerical method for solving electromagnetic problems. Solutions for these problems are computationally expensive in terms of processing time. Recently, we develop a method, High Speed Low Order FDTD (HSLO-FDTD) that is proven to solve one dimensional electro-magnetic problem with a reduction of 67% of processing time from the FDTD method. In this paper, we extend the method to solve two dimensional wave propagation problem. Since the problem is large, we develop the parallel version of HSLO-FDTD method on distributed memory multiprocessor machine using message-passing interface. We examine the parallelism efficiency of the algorithm by analyzing the execution time and speed-up.

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

A Simple Insulated Monopole Sensor Technique for Determination of Moisture Content in Hevea Rubber Latex

This paper describes the application of a SMA stub contact panel as an insulated monopole sensor for determination of moisture content in hevea rubber latex. Comparison results between measured and calculated reflection coefficient using King’s model are presented. Calibration equations relating moisture content to phase shift have been established in the frequency range from 100 MHz to 5 GHz. The accuracy of the technique was 1.3% when compared to actual moisture content obtained using the gravimetric method.

A simple procedure to determine complex permittivity of moist materials using standard commercial coaxial sensor.

A Simple Procedure to Determine Complex Permittivity of Moist Materials Using Standard Commercial Coaxial Sensor A simple procedure was developed to determine complex permittivity of moist materials for known percentage of moisture content at any frequency based using a standard commercial coaxial sensor. Polynomial fitting and Gaussian elimination method were applied to obtain a single equation of complex permittivity as a function of frequency and moisture content. The empirical equation was tested for new samples and was found to have mean error percentage of 5.14 % and 10.22 % for dielectric constant and loss factor, respectively, when compared to a commercial probe.

A Small and Slim Coaxial Probe for Single Rice Grain Moisture Sensing

A moisture detection of single rice grains using a slim and small open-ended coaxial probe is presented. The coaxial probe is suitable for the nondestructive measurement of moisture values in the rice grains ranging from from 9.5% to 26%. Empirical polynomial models are developed to predict the gravimetric moisture content of rice based on measured reflection coefficients using a vector network analyzer. The relationship between the reflection coefficient and relative permittivity were also created using a regression method and expressed in a polynomial model, whose model coefficients were obtained by fitting the data from Finite Element-based simulation. Besides, the designed single rice grain sample holder and experimental set-up were shown. The measurement of single rice grains in this study is more precise compared to the measurement in conventional bulk rice grains, as the random air gap present in the bulk rice grains is excluded.