Bundle fibre-optic displacement sensor

Force measuring is used in various surface characterization techniques such as indentation,
scratch tests, tribological analysis, determination of gas content, etc. The main
problems related with force measurement under extreme conditions have been analysed.
A strategy that should be followed to solve these problems has been discussed and several
examples of successive solutions that recently were developed by the authors are
presented. The need to carry out the characterization under extreme conditions poses
serious problems for the designers of the measuring systems that may include the
incompatibility of the sensors with the test conditions, undesirable interactions with other
components, stability, precision and uncertainty issues, the measurement range, etc.
Resolving these problems must be based on a global approach in which the characterization
system is considered as a whole, while the designer must analyse and solve the
possible conflicts between the subsystems. The way how an appropriate force measuring
system can be selected is described. The proposed method is illustrated by an example
in which an indirect force measurement using optical fibre displacement sensor was used.
Another example describes measuring system developed for vacuum high-temperature
nanoindentation. At high temperature, proper heat management based on noncontact
heating and laminar flow cooling system is mandatory to avoid experimental data
being affected by external noise and thermal drift.