A handheld InfraRed (IR) Carbon Dioxide (CO2) gas detector was developed and used to carry out a study of water and urine samples in South Africa. The details of the model and the results of the study are discussed here. The overseas markets are not geared for the current South African conditions. Use is made of components that can be obtained locally. Imported components are very expensive and should an imported model be damaged, it has to be returned overseas to be repaired. As an illustration of this technology it was decided to perform research in water technology and then develope a handheld Infrared CO2 gas detector based prototype which would: highlight the benefits of using handheld IR CO2 gas detectors; be built locally; be powered by a 12 Volt supply; be very easy to maintain; and be cost effective. Experimental results on the accuracy and stability of the instrument formed part of this study. The IR CO2 Gas detector that was developed was used throughout the project as a prototype and testing vehicle for numerous designs. It proved to be superior to the current imported commercial instruments in terms of size, cost effectiveness and user friendliness. A further advantage of the instrument is its robustness.

An experimental analysis of the factors which affect the sensitivity of the Ported Coaxial Cable Sensor (PCCS) system is presented. The measured response profile of the test system is compared against variations of cable separation distance, soil conductivity and permittivity, and magnetic field intensity above the transmitter cable. These experiments show that higher conductivity and permittivity of the burial medium results in a decrease in the strength of the magnetic field above the transmitter cable, and that this results in a decrease in response number. The results of these experiments are compared with the results obtained from a theoretical analysis of a simplified model. An experimentally derived relationship between cable separation distance and response number, which is valid for all soil types, can be applied to predictably minimize variations in sensitivity, resulting in a response ratio for each cell which will not exceed 3:1.

The increased demand for modern optical components necessitates an interferometric system that can rapidly and accurately measure wavefront phase errors during the complete fabrication process, from generation to polishing. The suitability of infrared wavelengths for several optical testing applications is well known, as are the greatly increased speed and accuracy of phase-shifting interferometric techniques. Therefore, this dissertation discusses extensively three topics: (1) the demonstration theoretically and experimentally of the feasibility of using a pyroelectric vidicon for infrared phase-shifting interferometry, (2) the design and fabrication of a prototype next-generation optical shop infrared phase-shifting interferometric system, and (3) the definition and quantification of the fundamental system performance parameters and limitations. Additionally, some application examples of infrared phase-shifting interferometry are presented, and specific recommendations for future work are included with the conclusions.

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Astronomers need single photon detectors to detect very faint light sources from deep space. An avalanche photodiode in the geiger mode is especially suited for the detection of single photons. Three by three arrays of avalanche photodiodes were fabricated. Breakdown voltages of 200V were measured. Large reverse currents prevented operating the array in the geiger mode. An improved design which minimizes the reverse current is needed. A commercial avalanche photodiode especially made for the geiger mode was tested and compared to a general purpose avalanche photodiode. Using the general purpose avalanche in the geiger mode was found to be unacceptable because when exposed to a weak light source, 90% of the output pulses were dark current pulses. A computer interface circuit was designed to read the time and location where photons were absorbed by the array. The circuit performed its function qualitatively, but it had a false triggering problem.

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