Browsing by Author "Makonda, Martin Mussobi"

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    Simple outdoor surface temperature measurements: their problems and calibration
    (University of Dar es salaam, 1981) Makonda, Martin Mussobi
    In this thesis problems related to simple outdoor surface temperature measurements are dealt with. We discuss the use of thermocouples and simple infrared radiation thermometers in carrying out such measurements. The Stoutjesdijk surface temperature radiation thermometer is the remote sensor specifically investigated. A general review is first made about temperature sensors specifically investigated. A general review is first made about temperature sensors and their use in doing actual measurements sighting the examples of thermocouples and radiometers. The second and third chapters deal with calibration of the instruments (thermocouples and Stoutjesdijk) and establishment of their accuracies within the temperature range for which they are intended to be used. Special calibration devices and strategies are described and made use of. After the calibration, experiments are reported to test the potentialities of the Stoutjesdijk as a surface temperature thermometer indoors and finally outdoors. The experiments performed showed that before proper use is made of thermocouples and the Stoutjesdijk, through calibration of instruments must be performed, using proper calibration equipment. With thermocouples, a quadratic relationship between the Emf and the temperature difference is confirmed here to provide the Accuracy needed for most field purposes. Apart from the calibration problems encountered in connection with the Stoutjesdijk, we report in this work on problem related to its use as a field instruments have been observed to arise from the instrument’s responses on the instruments surface have been observed to affect highly the instrument’s performance. The Stoutjesdijk also suffers from what can be termed a memory affect. This becomes larger when it is longer exposed and subsequently moved to extremely different temperatures. A hypothesis is brought forward to explain these effects, finally, lack of knowledge of the exact emissivity of the measured surface and of the sky and surroundings’ effective temperature are shown to be potential sources of inaccuracy in the measurements. In the final chapter, suggestions are given to improve on the results when use is made of the instrument in the field. Shading from direct solar radiation did improve measuring results, but not to a sufficient extent. Insulating the instrument’s body with mylar covered polystyrene material was noted to improve the results greatly. Knowledge of the emissivity of the surface was found to be responsible for the high final accuracy of our measurements, which become as high 0.1 of a degree for the average of a large series of measurements. Finally, in an appendix to the work the discuss the use of the equipment described for educational purposes. Class demonstrations are suggested and a possible standard experiment is outlined making use of the calibration equipment and thermocouples