A comprehensive and novel system of automatic control has been
designed and constructed using distributed intelligence techniques
to control a complex item of equipment for the measurement of linear
thermal expansion over the temperature range 1.5K - 300K. The system
is designed to perform its own self-calibration automatically before
the experiment commences.
The low temperature dllatometer developed for this research project
incorporates the most sensitive length change sensor available; a
three-terminal capacitance transducer. This transducer technique has been refined to resolve length changes of 10-5A and more importantly,
measure length against temperature profiles to better than 10-2A.
The period of time required to collect a full set of data
measurements on any particular specimen was in excess of 100 hours.
Forming the heart of the automated control system is an assembly of
Intel MCS-Sl single chip microcontrollers connected together on a
serial link consisting of a simple pair of wires. The approach has
been to divide the system automation into a number of specific
control tasks and to allocate a different task to each controller.
The Instrument has been used as a diagnostic tool to investigate the
properties of lead glasses, and in particular to study the
possibility of negative thermal expansion existing at low
temperatures. Thermal expansion measurements were also performed to
observe the phase change within single crystals of polydiacetylene
and to research into low temperature phenomena occurlng within the
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.