Low-cost thermoluminescence measurement using photodiode sensing

[摘要] Many branches of scientific and industrial research require precise instrument(s)for control and measurement. Such instruments tend to be prohibitivelyexpensive. In the current global economic climate the funding to procureresearch equipment is fast dwindling. One current interest that our institutionhas is the synthesis and thermoluminescence (TL) characterization of phosphors,polymers and nano-materials. TL measurement requires precise control andmeasurement of sample temperature as a function of output intensity.In the present research, we describe the design and construction of a low-costTL instrument that allows automatic control of various steps of the experimentwhile logging instantaneous intensity output. This work started with twofundamental considerations. Firstly, whether a low-cost thermoluminescenceequipment is feasible. Secondly and more importantly, whether a photodiodecan form the intensity sensing apparatus. We answer these questions affirmativelyby first putting together a course of research and assimilating the necessary tools needed. Using the the resulting demonstrable TL instrument, we demonstratethe versatility for temperature sequencing, range and heating control of thesample over the temperature range of 23 to 600 ± 0.5 ◦C. A comparableinstrument in the institution operates at a maximum ceiling of 300 ◦C. Additionalrefinements to the prototype instrument enable the sample temperature to beheld constant at any temperature within this range with the aid of softwaretuned Proportional-Integral-Derivative (PID) control. The intensity measurementsare made using a temperature-compensated, large area photo-diode operatedin photovoltaic mode and covering a wavelength range 400 to 1100 nm. Theinterfaces of the instrument that made the instrument easy to use were developedcon-currently. For instance the Universal Serial Bus (USB) handler, the Visual BASIC.NET control program that also logs the temperature and intensitydata, and the PIC18F2520 micro-controller firmware code that was writtenin the C-language. Several other tools, listed in the body of the dissertationwere also used. Finally, we present various results of temperature control andmeasurement and a demonstration measurement on a ceramic sample.

[发布机构] University of the Free State