Analysis of Metrological Conditioning of Thermal Diffusivity Measurements Applying Modified Ångström’s Method at Scanning Mode Operation

A technique of the temperature dependent thermal diffusivity investigation has been analysed. The technique is based on the modified Ångström method utilising periodic temperature oscillations in a slab specimen. The additional modification consists of imposing linear temperature changes – application of linear scans. This scanning mode procedure enables investigation of the thermal diffusivity over a certain temperature interval. The thermal diffusivity is calculated independently from two relations based on the measured amplitude attenuation and the measured phase shift of the temperature oscillation passing through the investigated specimen. The paper discuses the problem of the thermal diffusivity identification uncertainty. As a result correction factors for the thermal diffusivity data derived from simplified formulae have been determined. The procedure of the thermal diffusivity measurement has been verified by numerical modelling. Comparison between the initial and response signals with illustration of the linear scan imposed to a basic oscillation with reference to a classical procedure of subsequent steps, illustration of the approximation error analysis methodology and results in the form of a thermal diffusivity correction factor, comparison between the uncorrected and corrected applying in numerical modelling of the temperature oscillation experiment are presented in the paper.