Low-cost thermoluminescence measurement using photodiode sensing
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Date
2015-05
Authors
Mbongo, M.
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
Many branches of scientific and industrial research require precise instrument(s)
for control and measurement. Such instruments tend to be prohibitively
expensive. In the current global economic climate the funding to procure
research equipment is fast dwindling. One current interest that our institution
has is the synthesis and thermoluminescence (TL) characterization of phosphors,
polymers and nano-materials. TL measurement requires precise control and
measurement of sample temperature as a function of output intensity.
In the present research, we describe the design and construction of a low-cost
TL instrument that allows automatic control of various steps of the experiment
while logging instantaneous intensity output. This work started with two
fundamental considerations. Firstly, whether a low-cost thermoluminescence
equipment is feasible. Secondly and more importantly, whether a photodiode
can form the intensity sensing apparatus. We answer these questions affirmatively
by first putting together a course of research and assimilating the necessary tools needed. Using the the resulting demonstrable TL instrument, we demonstrate
the versatility for temperature sequencing, range and heating control of the
sample over the temperature range of 23 to 600 ± 0.5 ◦C. A comparable
instrument in the institution operates at a maximum ceiling of 300 ◦C. Additional
refinements to the prototype instrument enable the sample temperature to be
held constant at any temperature within this range with the aid of software
tuned Proportional-Integral-Derivative (PID) control. The intensity measurements
are made using a temperature-compensated, large area photo-diode operated
in photovoltaic mode and covering a wavelength range 400 to 1100 nm. The
interfaces of the instrument that made the instrument easy to use were developed
con-currently. For instance the Universal Serial Bus (USB) handler, the Visual BASIC.NET control program that also logs the temperature and intensity
data, and the PIC18F2520 micro-controller firmware code that was written
in the C-language. Several other tools, listed in the body of the dissertation
were also used. Finally, we present various results of temperature control and
measurement and a demonstration measurement on a ceramic sample.
Description
Keywords
Thermoluminescence, Electroluminescent devices, Photodiodes, Dissertation (M.Sc. (Physics))--University of the Free State, 2015