Design and optimisation of NiTi pressure gauge

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Mondragon Unibertsitatea
This paper describes construction of NiTi pressure gauge possible application mostly in an automotive. The aim is to present data of an electrical properties based on multiple input variables – the mechanical stress and the temperature of surrounding environment. Last aim of this paper is to describe development of the software for optimisation of the sensors shape to reach given force range, to ensure that maximal strain wouldn’t be crossed and to come up with a solution of compensation of sensors resistance temperature drift and nonlinearities. NiTi wires are very thermal dependent, but they shows also several advantages including large recoverable strains and higher sensitivity and smaller time constants then foil strain gauges with on ranges linear dependence between resistance and strain. Compensation is realised by combination of thermally compensated quarter bridge with a look-up tables. For realising look-up tables measuring system was equipped by independent thermometer to be able to choose appropriate characteristic and to judge on its limitations. Acquired data shows that quarter bridge cannot be used by itself, namely when subzero temperatures might be reached. This is due to material properties of NiTi which affects maximal recoverable stress of the wire and which is dependent on temperature. We did several measurements of thermal characteristics, stress-strain and resistance-strain characteristics. It was used for software development. The used model allowed to skip some of the model creation processes, resulting model has been validated by measurement.
Gauge design, NiTi, Pressure gauge, Thermal compensation, Binary alloys, Titanium alloys