The purpose of this study is to reduce the uncertainty of reference velocity measure-ments in low velocity ranges using a duplex differential manometer and to evaluate the need for an additional term in King's law to approximate a calibration curve of a constant-temperature hot-wire anemometer. Based on these findings, the study further investigates a hot-wire recalibration method that allows long-term measurements, focusing on the calibration curve function. While previous studies have relied on the output voltage itself for recalibration, this study adopts a method based on the squared output voltage according to King's law. The accuracy of these two hot-wire recalibration methods is compared, and the results indicate that they are equivalent. In addition, to validate the feasibility of long-term hot-wire measurements, mean flow quantities were measured over nearly six hours using a Pitot tube and a hot-wire anemometer. The uncertainties of all measurements were confirmed to be less than 1%. These results underscore the reliability of the hot-wire recalibration method as a calibration technique and pave the way for long-term hot-wire measurements.
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