Transient measurement method for the thermal properties of the thin-film membrane in a multi-parameter wind sensor

The performance of our previously devised thermal multi-parameter wind sensor for gaseous fluids is noticeably influenced by the thermal heat shunt induced by the thin-film membrane where heating and temperature sensing elements are embedded. Consequently, reliable values for the thermal parameters of the thin-film membrane are mandatory for their design and characterization. We present a new method to determine the thermal conductivity, thermal diffusivity, and average spectral emissivity of the thin-film membrane. Compared to commonly used measurement techniques for these thermal thin-film parameters, our method does not require custom-built specimens, i. e., the results can be obtained from transient excess temperature measurements carried out directly on the wind sensor device. We describe the theoretical background of this method, provide an efficient analytical model for the data evaluation including its validation by computer numerical analyses, and showcase sample measurements on multi-layer Si_xN_y-SiO₂ thin films.