Ionel Valeriu Grozescu

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.

Thermal diffusivity measurement of black and metallic graphite paint coatings

The suitability of a single-access approach involving a pulsed laser technique for non-contact and non-destructive measurement of thermal diffusivity is further examined. It was used to measure the thermal diffusivity of black and metallic graphite paint coatings. The values obtained in the present work are and for black and metallic graphite paint coatings respectively. All measurements were performed at room temperature.

Effect of Q-switched pulse laser temporal shape on induced temperature profile of laser absorbing materials

This paper examines the effect of a Q-switched pulsed lasers temporal output on the induced temperature change profile of laser absorbing materials. The effect was also discussed in the light of the case of the temperature profiles that were induced by ideal Dirac- function, square and Gaussian laser pulses. The induced temperature profiles were found to be unique with respect to the laser pulse temporal shape and therefore none of them resembled each other, even among the temperature profiles that were induced by Q-switched laser outputs with different pumping level.

Numerical solution of transient temperature for pulsed heating in a single spherical particle model

Photothermal technique provides a convenient means for detecting the change in pulse‐induced thermal radiation emission from a single spherical particle. The change in the emitted blackbody radiation is determined by the change in the surface temperature of the particle which in turn can be derived from heat conduction equation. Numerical solution to the heat conduction equation for a single spherical particle model on thermally bad conducting samples is derived and compared with a relatively simple analytical solution. Some results for particles of interest are discussed.

Microwave application for the detection of biodiesel-glycerine and biodiesel-water interfaces in the biodiesel production

In biodiesel industry there is a need to detect interfacing layer between biodiesel and glycerine after the transesterification and interfacing layer between water and biodiesel after the washing process. The detection of these two interfaces is important for separation process. In this work, a simple, low cost, and accurate microwave reflection type system for production of coconut biodiesel has been applied for the detection these interfaces. A module that works at 10.7 GHz, consisting of a microwave generator and a detecting diode, is used to measure the microwave reflection coefficient at various positions through the tank. The experimental results show the ability of the system to detect the level or height of these interfaces at the accuracy of 0.1 mm.

Sintering time effect on thermal diffusivity in BSSCO doped with Sm at low temperatures as revealed by flash method

We report the effect of sintering time on thermal diffusivity of BSCCO (Bi-Pb-Sr-Ca-Cu-O) superconductors doped with Sm with different concentration. The superconductor samples were sintered for 24, 48 and 100 hours respectively at 850 Celsius. Thermal diffusivity measurement was carried out at 80 - 300 K by using photoflash technique. The sintering time was found indirectly affect the thermal diffusivity in the way it influenced the grain size and grain alignment.

Heat conduction and laser beam deflection model using combined finite difference method for transient photothermal displacement technique

A numerical model of the heat conduction and laser beam deflection in a fluid heated by a thin, cylindrical resistance wire is presented. The model, developd using combined finite difference method technique is used to determine the temperature distribution in a test fluid sample and the heating wire. A probe laser beam passing through the sample is deflected by the refractive index gradient caused by the temperature gradient. The transient probe beam deflection can be recorded using a position sensitive detector. Simultaneous determination of the thermal diffusivity and thermal conductivity of the test fluid is possible by comparing the theoretical results of the probe beam deflection and the experimentally measured deflection.