A simple, dual wavelength, multiple-angle, light scattering system has been developed for detecting cryptosporidium suspended in water. Cryptosporidium is a coccidial protozoan parasite causing cryptosporidiosis; a diarrheal disease of varying severity. The parasite is transmitted by ingestion of contaminated water, particularly drinking-water, but also accidental ingestion of bathing-water, including swimming pools. It is therefore important to be able to detect these parasites quickly, so that remedial action can be taken to reduce the risk of infection. The proposed system combines multiple-angle scattering detection of a single and two wavelengths, to collect relative wavelength angle-resolved scattering phase functions from tested suspension, and multivariate data analysis techniques to obtain characterizing information of samples under investigation. The system was designed to be simple, portable and inexpensive. It employs two diode lasers (violet InGaN-based and red AlGaInP-based) as light sources and silicon photodiodes as detectors and optical components, all of which are readily available. The measured scattering patterns using the dual wavelength system showed that the relative wavelength angle-resolved scattering pattern of cryptosporidium oocysts was significantly different from other particles (e.g. polystyrene latex sphere, E.coli). The single wavelength set up was applied for cryptosporidium oocysts'size and relative refractive index measurement and differential measurement of the concentration of cryptosporidium oocysts suspended in water and mixed polystyrene latex sphere suspension. The measurement results showed good agreement with the control reference values. These results indicate that the proposed method could potentially be applied to online detection in a water quality control system.
A simple multiple-angle light scattering system was developed for the differential measurement of particle concentrations in suspension even in high concentration where multiple scattering effects are significant based on size. The system combines multiple-angle detection to collect scattered angle dependent light intensities, and Partial Least Square Regression method (PLS-R) to compose the predictive models for analyzing scattered signal obtain concentrations of samples under investigation. The system was designed to be simple, portable and inexpensive. It employs a diode lasers (red AlGaInP-based) as a light source and a silicon photodiode as a detector and optical components, all of which are readily available. The technique was validated using 1.1 μm and 3.0μm polystyrene latex beads in both mono-dispersed and poly-dispersed suspensions. The measurement results showed good agreement between the measured results and reference values. Their deviations from the reference values are 2.4% and 1.5% relating to references' concentrations of 8 10 3 .
Electric field is a fundamental quantity that is studied in the secondary and university levels. For the study, an experiment of finding equipotential lines from the charged electrodes is conducted. For the general experiment, the electric potentials are measured at various positions around the electrodes using a voltmeter. The measured data are then manually plotted to a graph to show the equipotential line. This experimental method is time-consuming (more than 1 hour in experiment). It is complicated to study of multiple electrodes using this experiment. Therefore, this research developed an experimental set that can display equipotential lines from various electrodes in real time. The developed experimental set uses a microcontroller (Arduino MEGA) to control a stepper motor to determine measuring positions of electric potential and measure electric potential at various positions around the electrodes (point of charge), automatically. The measured electric potentials and positions were plotted in contour graph to display patterns of the equipotential lines via a computer. The experimental set was tested using 2, 3 and 4 electrodes. The results showed that the developed system was able to display the equipotential lines of the electrodes within 2 minutes. The patterns of the equipotential lines were consistent with the equipotential lines generated from the theory. The correlations of the electric potential values from the experiments and the theoretical simulations for the systems of 2, 3 and 4 electrodes were 0.9452, 0.8691 and 0.9193, respectively. These results demonstrate that the presented experimental set can be used to display the equipotential lines from the electrodes effectively.
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