•Methods for anemometers dynamic behavior improvement were presented.•The methods are based on the use of active control with feedback loop.•The research results for rotary and thermal anemometer ...were presented.•The proposed methods allows for minimization of the dynamic errors.
Tachometric and thermal anemometers are two types of instruments mainly used in typical standard measurements in meteorology, ventilation, air conditioning, technical and industrial measurements. Both types of these instruments have many beneficial metrological properties, which causes their widespread use in many measurement issues. However, the sensors of mechanical anemometers have large dimensions and considerable high mechanical inertia. This is the reason for their poor dynamic properties. This results in dynamic measurement errors that are the cause of the measured average value being normally overstated. Thermal anemometers are dedicated for measurements in fast-changing flows. Hot-wire constant-temperature anemometers due to the low thermal inertia of the sensor and the applied feedback, have a wide frequency bandwidth for velocity fluctuations measurement, reaching hundreds of kilohertz. For standard constant-temperature anemometers this bandwidth strongly depends on flow velocity. In high-amplitude fast-changing flows, this can cause significant dynamic measurement errors. This paper presents two methods for improving the dynamic behavior of respectively rotary and thermal anemometers by active control. These methods are based on the introduction of additional feedback loop to the instruments.
We have developed a new method for measuring temperature and velocity at a high spatial resolution (minimum 2.56 mm pitch along an optical fiber). The developed method uses the same principle as a ...hot wire anemometer, where the velocity perpendicular to an optical fiber is estimated as a function of the cooling curve of a gold-coated layer on the optical fiber Joule-heated intermittently. The developed optical fiber sensor demonstrated the ability to acquire a transient velocity profile in airflow experiments with high repeatability and accuracy. This paper describes optical fiber-based velocity measurement in the velocity range of approximately 0-7 m/s with an error of approximately 10% compared to a hot wire anemometer and a new method for simultaneous temperature and velocity measurements. Applicability to velocity distribution measurements and seconds transient velocity changes are also described.
A compact anemometer capable of detecting both the magnitude and the direction of the wind in 2-D is presented. The device relies on a recently formalized principle, consisting in combining the ...differential pressures measured across distinct diameters of a cylinder exposed to the wind to estimate the wind velocity and the incidence angle. The cylinder includes an ad hoc microfluidic structure with three sections of diametric pressure probes connected in parallel. The multisection approach has been adopted in order to increase the reliability of the device. The prototype has been fabricated with stereolithographic printing, while commercial differential pressure sensors with low power consumption are used to read the pressures. The results of detailed experiments performed in a wind tunnel in the range 4-30 m/s are reported. A maximum angular error of 6° and a speed relative error less than 5.3% have been obtained.
This article proposes a hot-wire anemometer based on optical fiber embedding a fiber Bragg grating (FBG) and having a D-shaped transversal Section on whose flat surface a thin metallic layer has been ...deposited. Due to this geometrical structure, the optical power flowing through the fiber core can achieve the metallic layer and can be converted into heat. The embedded FBG can measure the resulting temperature increase and the temperature fluctuation of the D-fiber caused by the wind flowing. Numerical simulations have been performed in order to select the appropriate design parameters, such as thickness of the metallic layer and its distance from the core. Then, the fabrication process of the device and the experimental results of its characterization in temperature and wind assess its working principle. The developed sensor can work at low power levels of the source and is characterized by small size and high accuracy. Furthermore, it shows high cost-effectiveness and the possibility to modulate its wind sensitivity by setting the source power.
Mechanical tachometric anemometers, based on the phenomenon of the exchange of momentum between the flow and rotating measuring element, represent an important class of instruments used in flow ...metrology. In particular, they are used in meteorological and ventilation measurements. Mechanical anemometers with rotating measuring element are, however, known for their drawback related to their poor dynamic properties resulting from relatively large dimensions and mechanical inertia of the measuring element. In these instruments, the phenomenon of overestimating the measured average velocity caused by the inertia of the rotor takes place. Optimization of the dynamics of the measurement process, as well as the estimation and minimization of the measurement uncertainty, can be performed based on mathematical model of anemometer. In this study, a new, original concept of optimization of dynamic properties of tachometric anemometers is proposed, and the results of model and simulation studies are presented. The new concept of measuring instrument is based on the use of feedback and active control of the rotor. The new method was tested using model research, where two types of flow velocity excitations were applied: sinusoidal and rectangular. The tests carried out showed that the developed method allows for minimization of the dynamic uncertainty of the measurement and minimizes the phenomenon of average flow velocity overestimation occurring in time-varying flows. It has been shown that the use of optimization system allows for approximately tenfold reduction of the error of average velocity measurement in the case of pulsating flows. In addition, the optimization systems allow for anemometer's transmission bandwidth to be extended about a hundred times. This creates new application possibilities for these instruments and allows for a large reduction of measurement uncertainty.
An optical fiber thermal anemometer with a light source-heated Fabry-Perot interferometer (FPI) is proposed. The FPI is fabricated on the tip of a single-mode fiber using an ultraviolet-cured ...adhesive. A broadband light source acts as a heating light source as well, eliminating the need for a heating resistor or a pump laser which are usually required in optical fiber thermal anemometers. The interference fringe of the FPI shifts with airflow velocity because airflow not only reduces temperature of the FPI but also introduces strain due to wind force. Airflow velocity is therefore measured by detecting wavelength shift of the interference fringe. In the experiment, a high sensitivity up to −3.13 nm/(m·s −1 ) was achieved at the low velocity region, reducing to ∼−0.2 nm/(m·s −1 ) at the high velocity region within the measurement range of 0-7 m/s. The response and recovery time is 250 and 580 ms, respectively. It is worth noting that the anemometer maintains a relatively high sensitivity at the high velocity region due to the contribution of wind force effect that makes it outperform most of the fiber thermal anemometers.
This paper analyzes the field performance of two cup anemometers installed in Zaragoza (Spain). Data acquired over almost three years, from January 2015 to December 2017, were analyzed. The effect of ...the different variables (wind speed, temperature, harmonics, wind speed variations, etc.) on two cup anemometers was studied. Data analysis was performed with ROOT, an open-source scientific software toolkit developed by CERN (
) for the study of particle physics. The effects of temperature, wind speed, and wind dispersion (as a first approximation to atmospheric turbulence) on the first and third harmonics of the anemometers' rotation speed (i.e., the anemometers' output signature) were studied together with their evolution throughout the measurement period. The results are consistent with previous studies on the influence of velocity, turbulence, and temperature on the anemometer performance. Although more research is needed to assess the effect of the anemometer wear and tear degradation on the harmonic response of the rotor's angular speed, the results show the impact of a recalibration on the performance of an anemometer by comparing this performance with that of a second anemometer.
We propose a method to assess the accuracy of atmospheric turbulence measurements performed by sonic anemometers and test it by analysis of measurements from two commonly used sonic anemometers, a ...Metek USA-1 and a Campbell CSAT3, at two locations in Denmark. The method relies on the estimation of the ratio of the vertical to the along-wind velocity power spectrum within the inertial subrange and does not require the use of another measurement as reference. When we correct the USA-1 to account for three-dimensional flow-distortion effects, as recommended by Metek GmbH, the ratio is very close to 4∕3 as expected from Kolmogorov's hypothesis, whereas non-corrected data show a ratio close to 1. For the CSAT3, non-corrected data show a ratio close to 1.1 for the two sites and for wind directions where the instrument is not directly affected by the mast. After applying a previously suggested flow-distortion correction, the ratio increases up to ≈1.2, implying that the effect of flow distortion in this instrument is still not properly accounted for.
A continuously recording, impedimetric thermal liquid flow sensor fabricated on a Parylene C thin film substrate is presented for the first time. The sensing concept, inspired by hot-film anemometry, ...includes an additional upstream unheated reference electrode pair which enabled attenuation of environmental drift in impedance by more than <inline-formula> <tex-math notation="LaTeX">5\times </tex-math></inline-formula>. This sensor design and transduction approach was motivated by the need for an alternative to traditional hot-film anemometers for in vivo applications. An analytical model was developed to describe the axial fluid temperature surrounding the impedimetric sensor and its effect on solution conductivity. The impact of heater power was modeled and matched with experimental data; similar analysis was conducted for other parameters including channel height, ambient temperature, and electrolyte concentration. The sensor achieved a <inline-formula> <tex-math notation="LaTeX">2\sigma </tex-math></inline-formula> resolution of <inline-formula> <tex-math notation="LaTeX">17~\mu \text{L} </tex-math></inline-formula>/min over the range 43-200 <inline-formula> <tex-math notation="LaTeX">\mu \text{L} </tex-math></inline-formula>/min. The models and fabricated device significantly expand our understanding of thermal impedimetric flow sensing. 2020-0357
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