A digital anemometer

A digital anemometer has been developed for air flow measurements in home and office environments. The principle is based on hot-wire anemometry. The probe consists of a cold thermistor for flow temperature detection and a hot thermistor for flow rate detection. The latter is self-heated by a thermal bridge. Its unbalance voltage due to the air flow is compared with the reference response transformed into the time domain by direct digital synthesizing. This pulse-width modulation provides the linear digital representation of the flow rate under measurement. The unbalance component due to flow temperature is compensated by scaling the reference response depending on temperature detected by a cold thermistor. These linearization and compensation techniques make accurate measurements possible with a simple configuration. Performances of a prototype anemometer built using a one-chip 4-bit microcomputer are also presented to demonstrate the validity of these techniques     

超声波风速仪的理论建模及分析

深入分析了超声波在空气中的传播特性,研究了基于传播时间和声强变化的超声波风速仪理论模型,从传播时间和声强两个方面描述了超声波风速仪的基本原理,并在不同风速和相对风向的条件下进行了实验,取得了和理论模型一致的结果,为研制超声波风速仪提供了理论基础。     

Pressure dependence of hot-wire anemometer readings

Translated from Izmeritel'naya Tekhnika, No. 5, pp. 21–23, May, 1991.     

Thermoelectric anemometer for measuring air flow speeds

Conclusions The thermoelectric anemometer was tested under mining conditions for measuring the speed of air along underground workings. The tests have shown that the instrument is more accurate than existing impeller or cup-type anemometers and is suitable for measuring low air speeds. It is also possible to measure air depressions by means of this instrument, thus providing depression surveys by means of one instrument instead of two, namely, a microammeter and an anemometer which are normally used in mines. The instrument has three ranges: 0.001–0.3; 0.1–6 and 1–20 m/sec; its error is 1.5% and its over-all dimensions are 90×110×130 mm, with a weight of 1.2 kg.     

Intelligent heating control of a new ice-free anemometer

The wind industry has grown over the years along with the collective desire to produce clean energy. High wind potential sites are often located in northern regions where harsh climatic conditions arise. The performance of anemometers, which provide essential measurements to wind turbine operation and wind resource assessment, is then jeopardized by ice build-up and snow accumulation. These conditions result in the need for heated instruments able to remain ice-free regardless of weather conditions while minimizing energy consumption. The main objective of this work was to develop an intelligent heating control for a new generation of ice-free anemometers. The controller is based on vision recognition of ice build-up on the cups of the anemometer using a neural network. Heating power is applied according to the icing state and the icing history of the instrument. Primary results have shown that, for a completely ice-free performance, the developed controller uses an average of less than two thirds of the energy consumed by common control systems similar to those used by other ice-free anemometers available on the market.     

Hot-wire anemometer with temperature compensation using only onesensor

In conventional constant temperature hot-wire anemometers, the compensation for the fluid temperature is done by using two sensors. In this paper, the analysis of an anemometer circuit using only one sensor, operating alternately at two different temperatures is presented. The effect of the amplifier input offset voltage is taken into account, and its influence on the measurement of fluid velocity is quantified. Preliminary experimental results are also presented     

Response of phase Doppler anemometer systems to nonspherical droplets

The Phase Doppler Anemometer (PDA) technique measures particle diameter assuming sphericity. A means for detecting nonsphericity has usually been implemented in commercial PDA systems to avoid sizing errors if the sphericity assumption is not valid. In the present research the response of standard and planar PDA systems is examined experimentally in more detail by passing nonspherical droplets of known shape through the measurement volume. The effectiveness of nonsphericity detection schemes can be evaluated, and furthermore the influence of the droplet oscillations on the frequency and phase evolution of individual signals can be quantified. The light scattering from such particles has been simulated by using geometric optics, and the computed response of standard and planar PDA systems agrees well with the experimental observations. We conclude with some remarks concerning the possibilities of characterizing the nonsphericity with PDA systems.     

Implementation of a new type of time-of-flight laser anemometer

A new time-of-flight (TOF) laser anemometer system utilizing a spatial lead-lag filter for bipolar pulse generation has been constructed and tested. This new TOF has been modified to enable measurements in turbulent flows near walls. Good results have been obtained as close as 100 microm from a surface, with a 140-mm focal length final lens. Lading's theory for the behavior of the measurement variance has been confirmed for this configuration.     

Evolutionary optimised nonlinear function for linearisation of constant temperature anemometer

A simple software method to derive linearised output for constant temperature anemometer (CTA) is presented. The method uses a nonlinear ratiometric-logarithmic function, which consists of two parameters whose optimal values are determined by minimising the objective function (mean square error) to improve the linearity of CTA signal. Covariance matrix adopted evolutionary strategy algorithm, which generates optimal values consistently, is employed to determine the optimal values of linearisation parameters. The proposed linearisation algorithm was implemented using LabVIEW 7.1 Professional Development System in a personal computer that provides the facility to interface with the National Instruments data acquisition module PCMCIA-NI DAQCard-6024E. Experimental studies have been carried out using practical air-flow velocity measurement data obtained form Dantec Dynamics practical guide. The performance measures such as full-scale error and root mean square error are considered to compare the performance of the proposed method with the methods reported for linearisation of transducers. Experimental results reveal that the proposed evolutionary optimised nonlinear function-based software lineariser works well for CTA, and it can be suitable for computer-based flow measurement/control systems.     

基于凹面反射的超声风速测量系统设计与实现

时差法是超声风速风向测量系统的基本方法。在介绍时差测量原理的基础上,分析了系统测量误差的来源;构建了增大测量范围的凹面反射模型;结合该模型,在系统结构、电路系统、控制流程及数据处理算法等方面进行了全面的设计和实现,并制成了原理样机。风洞试验结果表明,凹面反射结构可以增加系统的测量范围,提高大风条件下测量数据的稳定性。原理样机具有体积小、可靠性高、测量范围大的优点,已在风力发电方面获得了实际应用,并取得了较好的应用效果。     

A laser-type anemometer for measuring the velocities of air streams

A laser-type anemometer is described which measures the mean velocity and velocity fluctuations in turbulent streams.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 24, No. 5, pp. 888–890, May, 1973.     

Hot-wire anemometer measurement of mean velocity very close to a wall

This paper analyzes the errors arising in the use of a hot-wire anemometer for measurements in flow near the wall and associated with proximity to a heat-conducting surface and large velocity gradients.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 6, pp. 985–990, June, 1979.     

风沙环境对超声风速仪测量结果的影响

超声风速仪由于其在风速、风向测量方面的卓越性能被引入风沙物理学及沙尘暴研究中以获得相关风场信息。然而,对其在风沙环境下测量结果的准确性目前并无文献资料讨论。通过对超声风速仪测量原理及超声波在含颗粒物介质中传播速度变化的理论分析,讨论了沙尘暴环境下沙尘颗粒物体积浓度对超声风速仪测量结果的影响。数值计算结果表明,当沙尘颗粒体积分数超过50%时,超声风速仪测量值的相对误差超过10%,且随着颗粒物体积分数的增加,其测量误差呈指数形式递增。这一结果对于风沙环境中超声风速仪的正确使用具有非常重要的参考价值。     

Laser Doppler anemometer measurement of the velocity pulsations of large particles

A procedure has been developed for estimating the velocity pulsations of polydisperse particle velocities. The mean velocities of glass particles as well as their root-mean-square deviations were measured in trials for various sensitivities of the laser Doppler anemometer system used. Translated from Izmeritel'naya Tekhnika, No. 6, pp. 35–39, June, 1999.     

Effect of averaged flow temperature on readings of a hot-wire anemometer

Experimentally verified expressions that take into account the effect of the averaged flow temperature on the readings of a hot-wire anemometer are proposed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 4, pp. 622–627, April, 1982.     

Quantization error in processing the signal from a laser Doppler anemometer

The effect of quantization noise arising in the course of digital processing of the signal of a laser Doppler anemometer on the error in Doppler signal frequency estimation in the time domain is considered. It is shown that in high-precision measurements the quantization noise that appears in amplitude quantization of the signal of a laser Doppler anemometer is comparable with other noise sources and must be taken into account in estimation of the limiting accuracy of a laser Doppler anemometer. Results of a simulation and experiment are presented. Translated from Izmeritel'naya Tekhnika, No. 9, pp. 15–17, September. 1998.