AUTOMATED MULTI MEASUREMENT SYSTEM FOR RESEARCH OF DRYING

Transcription

1 AUTOMATED MULTI MEASUREMENT SYSTEM FOR RESEARCH OF DRYING PROCESSES JURIJS SULINS, ANDREJS KOSTROMINS Latvia University of Agriculture, Faculty of Information Technologies, Liela 2, Latvia, Abstract Scientists almost of all science sectors have the same problem: several devices mutually incompatible, is not possible to make automatic data acquisition and processing by own needs and also experiments are able to observe only in presence. It is therefore very important to create an easily manageable system, connecting many devices, retrieve and store data in electronic format. Finally process data by own needs for example, create a diagram, where is possible to investigate research result. We create our own computer system: investigated apples (research object) drying process, we measured two electrical components capacity and resistance, temperature, humidity and mass of research object. At the end of the experiment we created several diagrams by our computer system to analyze obtained data. Keywords: IT, Computer science, Computer control, multi-measurements, LCR. Introduction Nowadays, science sector occupies a major role in human development. There are being conducted experiments and studies, which can lead to significant discoveries and inventions. The integral part of these processes is to fix and analyze measured data. The measurement results can be achieved by reading them from the measurement scales or an electronic display, what during the experiment becomes a routine job. Today in reliable studies it is more wisely to use computerized systems for performing automated measurements without human direct interference in the measurement process. As students of faculty of Information Technologies of study program Computer Science and Computer Control, we set ourselves the objective of creating computer systems which perform mentioned functions: automated measurements, measurements storage on the physical computer memory, the obtained data further processing and graphics creation. Chemical and physical properties of substances can be studied using various direct measurements such as temperature measured by thermocouples, to determine the mass by scale, etc. In such experiments there also can be used indirect measurements - measurements of the electrical parameters, such as active resistance or capacity, when after the calibration, we obtain information about the object humidity (Moin et al., 1988, Petrov et al., 1985). Our experiment is related to dynamics of various porous objects drying processes, which have emerged in both food technology (Moin et al., 1988, Petrov et al., 1985, Ginzburg et al., 1980) and building material manufacturing processes (Iljins et al., 2009, Iljins et al., 2008, El-Beltagy et al., 2007). Our study is devoted to measure dynamics of apples drying processes. Materials and Methods In this experiment s development stage we offer a method, where we use a modern gauge and familiar software packages. Since the research is specific, we had to program our own software, because manufacturers software was unusable for our research. In experiment was used: electronic multimeter - LCR HiTESTER Hioki , electronic scales - Kern , electronic temperature and humidity gauge - TFA Dostmann By Hioki Hitester were measured two electrical parameters: Rs serial circuit active resistance and Cs - serial circuit capacity. Scheme of automatic measurement system in Figure 1 is presented. 235

2 Figure.1. Scheme of automatic measurement system. These values were measured at alternating current flowing which is proportionally dependent on the resistance of apple and at 1v pressure at 58 different frequencies in the range from 42Hz to 1MHz. Electrical parameters were measured every 10 minutes, but frequency was switched every one second so all measurements at whole frequency range were performed at about one minute. To automate the measurements we use a manufacturer s software which store data in Microsoft Office Excel workbook. For processing obtained data we create our own software using C# programming language and special MATLAB.dll reference library which read data from Excel s workbooks worksheets and then transfer data to MATLAB (v. 2009a) plot through which the measurement results are represented in the 3D graphs. MATLAB is a numerical computing environment and fourth-generation programming language, and C# is multi-paradigm programming language encompassing imperative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines, which was developed by Microsoft within the.net initiative and later approved as a standard by Ecma (ECMA- 334) and ISO (ISO/IEC 23270). Dynamics of Apple s active resistance as function of time and frequency and dynamics of apple s capacity as function of time and frequency in Figure 2 and Figure 3 are presented. 236

3 Figure.2. Dynamics of apple s active resistance as function of time and frequency. Figure.3. Dynamics of apple s capacity as function of time and frequency. Also C# programming language we use to create our own software to control the electronic scales Kern , that is to send balance command to scales and receive back readings in electronic format and store them in text file. The balance commands were sent every ten minutes. Indoor temperature and humidity were fixed by TFA Dostmann device every two hours and in the end of measurements were imported to computer for 237

4 further processing. Throughout the course of the experiment if necessary it was possible to connect remotely to the computer system and observe the research and make the processing and analyzing of already acquired data, using MS Windows Remote Desktop Connection utility from any location where the Internet was available. To accelerate the water evaporation from the apple, it was cut, and for research was used middle part of the apple without peel, and also we conducted additional air circulation - artificially created air flow with 5V electronic fan that was focused on research object. The research occurred from to and there were made 1620 Cs, Rs and mass measurements and 180 indoor temperature and indoor humidity measurements. Dynamics of indoor temperature as function of time and dynamics of indoor humidity as function of time in Figure 4 and Figure 5 are represented. Figure.4. Dynamics of indoor temperature as function of time. Figure.5. Dynamics of indoor humidity as function of time. Similar experiments, where the computer automated system perform measurements, the researchers carried out using various methods (Hellerstein et al., 2001, Mamaev et al., 2005). One of them is to perform measurements and data analyzes by using LabView software (Laboratory Virtual Instrumentation Engineering Workbench), what is a platform and development environment for a visual programming language from National Instruments. With Lab view is possible to perform multiple measurements by connecting the relevant sensors to the special interface cards (Johnson et al., 2006). Results and Discussion Before carrying out the experiment we have performed test measurements when the AC frequency range was from 42Hz to 5Mhz. Apple wasn t peeled and wasn t cut as a result in two weeks the moisture loss was negligible and also in the test final part from resistance diagram was observed that the active resistance is declining that shows that humidity has risen in apple. This could be explained by starting of the decay process. In the both charts (active resistance and capacity charts) we see that, by increasing the frequency, measurements 238

5 become less sensitive therefore does not make sense to perform research at very high frequencies (above 1 MHz). We concluded that the drying process should be researched with apple that has no peel, so then the water is easier to evaporate, and promoting drying by changing external conditions - heating or generating additional air flow. At the heating case the electronic scales heats up too as a result scales were showing the wrong data, while creating additional air flow (in our case with the 5v electronic fan) weight readings are not affected. Obtained information in the test measurements coincides with the observations of other scientists (Moin et al., 1988, Petrov et al., 1985). Moisture detection methods used by researchers are different (Moin et al., 1988, Petrov et al., 1985, Ginzburg et al., 1980). Scientists in their publications (Petrov et al., 1985) write that in the practice it is useful to gather active resistance and capacity data, in addition, each in different phase, also measurements must be done at the alternating current and at working frequency of 50Hz (can be used frequencies up to the limit of audibility (20kHz), because with higher frequencies the sensitivity decreases and the measured data changes are virtually invisible (Figure 1, Figure 2). Using the direct current for long time to measure active resistance, the electrodes start to polarize, resulting that active resistance begins to rise and causes errors in measurements. Drying Process can be divided into two phases (Iljins et al., 2009, Moin et al., 1988, Petrov et al., 1985). At the first phase vaporization continuous at a constant speed and the apple s mass chart is linear function (Figure 8), which can be explained by a sufficient amount of water at surface of the apple. In this phase, the active resistance is insensitive (Figure 7), so it is appropriate to analyze the capacity (Figure 6). This is explained by the fact that the environment s (water) dielectric permeability ε = 81, and according to formula (1). Formula of capacity for capacitor is (1) where, C 2 (N m 2 ) -1 - electric constant; ε - dielectric permeability of the environment, C 2 (N m 2 ) -1 ; S - condenser surface area, m 2 ; d - distance between capacitor plates, m 2. In the second phase the water evaporation rate depends on the diffusion process through the apple s pores towards it s surface, and curve is changing the nature from linear to logarithmic (Figure 8). In this phase chemical composition and particle size begin to play a major role, which is not directly related to the humidity of the surveyed object or substance, therefore, it is necessary to begin to analyze the active resistance R, Ω. In the second phase, by decreasing humidity, resistance begins very rapidly increasing (Figure 7). It is also important to note, that, when in the apple was been left very little moisture, the active resistance became dependent on the ambient humidity (Figure 9) Figure.6. Dynamics of apple s capacity as function of time at frequency of 42Hz. 239

6 Figure.7. Dynamics of apple s active resistance as function of time at frequency of 42Hz. Figure.8. Dynamics of apple s mass as function of time. Figure. 9. Dynamics of all measurements as function of time at frequency of 42Hz. 240

7 Conclusions Our primary objective was to find a solution for automated measurement managing, which was based on the apple drying process dynamics. We have created our own system that is able to automatically take measurements without human presence at predefined terms and parameters, thus solving the problem, which often experienced engineers. We have complemented our experience in working with measuring instruments, programming and automated computer control. After the study we see the possibility of the development and improvement, for example, where there are errors in data reading, or other type of software problems, the system can send electronic messages via or mobile SMS system. Also could be installed surveillance cameras in the laboratory, for reason when, for example, is unexpected temperature changes, the computer could switch on video surveillance and record it, and send the report to researchers in the same way like previously mentioned. Returning to the measurements, our experimental results coincide with findings of other scientists. There are two phases in the apple s mass chart (Figure 8), when curve is changing it s characteristics during the experiment, which is directly related to the evaporation of moisture from the apple. Increasing frequency, both - active resistance and capacity become insensitive during the evaporation at time (Figure 2, Figure 3). Most stable performance is at the lowest possible measuring frequency 42Hz, in the curves characteristics there are no large spikes. Active resistance begins to rise sharply in the second phase, but the capacity varies very little, while in the first phase, the opposite phenomenon occurs when the active resistance is insensitive, but the capacity rapidly decreases, while apple is losing humid (Figure 6, Figure 7). Although the room humidity and temperature were not constant (Figure 4, Figure 5), which is reflected in the mass chart, and indiscriminate mass increases for short times (Figure 9). From our study, we concluded that the measurement can be taken at frequencies up to 20 khz, but the best option is to do measurements at 42 Hz frequency (Figure 2, Figure 3). It follows that similar experiments may be carried out with a much cheaper and more portable device, than HIOKO 3522, because the measurements at high frequencies are senseless. Once again, we were convinced of the truth of life - any experiment cannot be perfectly accurate, because there is no the environment free of side effects from other factors: temperature, humidity, vibration, thermo-radiation etc. Acknowledgements We would like to thank our project coordinator Uldis Gross (Dr.phys., Asoc.prof.) who assisted with the development of this experiment. We are grateful for the support that we received from Sergejs Arhipovs (Assist. prof.) in programming field. References 1. El-Beltagy A., Gamea, G. R., Essa, A. H. A. Solar drying characteristics of strawberry, Journal of Food Engineering, vol. 78, Issue 2, January 2007, Hellerstein J., Parekh S. (2001) An Introduction to Control Theory With Applications to Computer Science. Available at: Iljins U., Skujāns J., Ziemelis I., Gross U. (2008) Investigation of Moisture Diffusion in Foam-Gypsum Samples.- Proceedings of The International Scientific Conference Applied Information and Communication Technologies 08.- Jelgava, pp. 4. Iljins U., Skujāns J., Ziemelis I., Gross U., Veinbergs A. (2009) Theoretical and experimental research on foam gypsum drying process. - Chemical Engineering transactions, Volume 17, pp. 5. Johnson G. W., Jennings R. (2006) LabVIEW Graphical Programming Fourth Edition Available at: Mamaev A.I, Borikov V. N., Mamaeva V. A. and Dorofeeva T. I. (2005) A Computer System Measuring the Electrical Parameters of Microplasma Processes in Solutions Available at: Ginzburg A. S., Gromov M. A., Krasovskaja G. I. (1980) Teplo - fizicheskie harakteristiki pishhevyh produktov (Thermo - physical characteristics of food products). Moskva, Pishhevaja promyshlennost, p. 288 (in Russian). 8. Moin I. B., Rogov N. A., Gorbunov A. V. (1988) Termo - i vlagomerija pishevyh produktov (Thermoand moisture measurement of food products). Moskva, Agropromizdat, p. 304 (in Russian). 9. Petrov I. K. (1985) Tehnologicheskie izmerenija i pribory v pishhevoj promyshlennosti (Process measurement and devices in food industry). Moskva, Agropromizdat, p. 344 (in Russian). 241