Drift compensation in thermal anemometry

Abstract

The drift of the resistance of sensors used in thermal (such as hot-wire and hot-film) anemometry remains a perpetual concern for users of constant-temperature anemometers (CTAs). Even small changes in the resistance of such sensors result in error if the sensor was calibrated prior to the occurrence of the drift. In the present work, modified forms of the relationship between the output voltage of a constant-temperature anemometer and the fluid velocity, which take into account the sensor resistance as well as other resistances involved in the Wheatstone bridge (top resistance, operating resistance, cable and probe resistances), are used to minimize the sensitivity of the CTA to changes in the sensor resistance. These new relationships are tested using (i) two different CTAs and (ii) three hot-wires of differing resistances (3-17 Ω), and are shown to collapse the calibration data, even though the sensor resistances had drifted. It is expected that use of this method would reduce the frequency of calibrations needed to maintain satisfactory degrees of accuracy and repeatability in experimental measurements of fluid flows made using CTAs.

Multi-scalar mixing in turbulent coaxial jets

“…After finishing all experiments, a calibration for the interference probe was repeated to account for any possible drift, which in thermal-anemometry techniques may arise from a variety of factors, including changes in ambient temperature, humidity and probe resistance (Hewes et al. 2020). Additional information on the calibration procedures may be found in Hewes & Mydlarski (2021 a , b ).…”

“…a hot-wire, cold-wire thermometer or interference probe) after or between calibrations may result in measurement error known as drift. Drift in thermal anemometry occurs due to a variety of circumstances, including, but not limited to changes in ambient temperature or humidity, and fouling or aging of a wire (Hewes et al 2020). In the present work, drift may also occur due to small changes in the separation distance of the two hot-wires which make up the interference probe.…”

Design of thermal-anemometry-based probes for the simultaneous measurement of velocity and gas concentration in turbulent flows

“…Assuming that no drift (resulting from changes in the ambient temperature and/or wire aging [32]) occurs after the wires are calibrated, the above data reduction scheme can be used to infer the velocity and concentration at each point in the flow from the measured voltages of both wires (E up , E down ). First, equation ( 11) is used to calculate C, and then, using that value of C, equation ( 12) is used to calculate U .…”

“…and using the convective heat transfer correlation for a long cylinder developed by Collis and Williams [22]: Nu c T f T −0.17 Thermal-anemometry-based probes to measure velocity and concentration variable, denoted as n. Additionally, given that experimentalists typically measure the anemometer bride voltage (E) (see Hewes et al [32]) :…”

A Temperature Compensation Method for aSix-Axis Force/Torque Sensor Utilizing Ensemble hWOA-LSSVM Based on Improved Trimmed Bagging

“…Hardware and software methods are two ways to compensate for the impacts of temperature. Compensating methods focusing on hardware aim to eliminate the temperature's impact on the regulating circuit [4][5][6]. However, compensating on the circuit is usually costly and lacks flexibility.…”