Development of cylindrical hot-film sensors for measuring instant velocity of fluid flow

The cylindrical hot-film sensor has found wide industrial application because it combines the high frequency response with improved strength and stability. In this work, such sensors were fabricated for application in different fluids. The sensing part of the sensor consisted of a nanostructured sandwich with a 40–60 nm thick nickel film deposited by PVD process onto a 125 micrometer diameter cylindrical quartz wire. An outer 0.5 or 2 micrometer thick protective silica layer was applied onto the nickel film. The sensors obtained were subjected to various functional and quality assessment tests. Using a constant temperature anemometry (CTA) circuit, the sensors were calibrated conforming to well-known procedures. Furthermore, an evaluation of the sensor response was undertaken by measuring an already known turbulent flow and comparing the results with those of the literature. Finally, technical conclusions were drawn from the results.