Abstract:
Development of low cost instrumentation is a valuable exercise in a country
like Sri Lanka where scientists strive to sustain in their research with limited
funds. This student research project is motivated on such grounds and
integrated with the existing experimental facility developed locally. In this
work, a multiplexing electronic device was designed and constructed to
automate multiple measurements of several samples during slow cooling heating runs and isothermal measurements of an applied magnetic field
sweep. The self-designed low-cost multiplexing device is constructed to
automatically select one from several input signals and be measured either
by an instrument or by microprocessor via analogue to digital converter. The
device can be used with an amplification option if the resolution of the
measuring instrument is insufficient. The design was with a multiplexer IC
4051 to automatically select inputs at specific time intervals that is controlled
by 4017 Counter IC supported by 555 Timer IC, while the selected channel
inputs are identified via a seven segment display. Op-amp CA 3140 was used
for the amplification option. A specially designed regulated power supply
unit provides the dc power requirements for the device. Microprocessor was
connected using flash analog to digital converting method. Visual Studio
2007 software and the C++ programming were used to accept and analyze
the digital data from the multiplexing electronic device. Several test
experiments were performed to ascertain the multiplexing process and to
validate the amplification reliability. The uncertainty that arises due to
amplification is verified to be within 6%.
