High-precision anemometer with thermal wave

Rachalski, A.

doi:10.1063/1.2338260

Cited by 12 publications

(6 citation statements)

References 8 publications

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“…These effects were investigated both theoretically and experimentally in the macroscopic regime, and several models were considered to explain the nonlinearities. 15 Related recent work on macroscopic phase-shift thermal-wave anemometry sensors shows promising preliminary results, 16 potentially eliminating nonlinearities and dependence on fluid properties.…”

Section: Introductionmentioning

confidence: 99%

Time-of-flight thermal flowrate sensor for lab-on-chip applications

et al. 2011

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We describe a thermal microflowrate sensor for measuring liquid flow velocity in microfluidic channels, which is capable of providing a highly accurate response independent of the thermal and physical properties of the working liquid. The sensor consists of a rectangular channel containing a heater and several temperature detectors microfabricated on suspended silicon bridges. Heat pulses created by the heater are advected downstream by the flow and are detected using the temperature detector bridges. By injecting a pseudo-stochastic thermal signal at the heater and performing a cross correlation between the detected and the injected signals, we can measure the single-pulse response of the system with excellent signal-to-noise ratio and hence deduce the thermal signal time-of-flight from heater to detector. Combining results from several detector bridges allows us to eliminate diffusion effects, and thus calculate the flow velocity with excellent accuracy and linearity over more than two orders of magnitude. The experimental results obtained with several test fluids closely agree with data from finite element analysis. We developed a phenomenological model which supports and explains the observed sensor response. Several fully functional sensor prototypes were built and characterized, proving the feasibility and providing a critical component to microfluidic lab-on-chip applications where accurate flow measurements are of importance.

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Section: Introductionmentioning

confidence: 99%

Time-of-flight thermal flowrate sensor for lab-on-chip applications

et al. 2011

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“…Two interconnected phenomena are involved in the process of propagation of a temperature wave in flowing gas: Wave drift with the flow velocity, and thermal diffusion. For a sinusoidal wave, the dependence of the wave phase velocity on the flow velocity is described by the relationship [1,2]:…”

Section: Basics Of the Thermal Time-of-flight Methodsmentioning

confidence: 99%

“…In order to generate a thermal wave in the flowing gas, the temperature of the transmitter must change over time. In the thermal wave method, various types of electric current waveforms heating the wave transmitter are used: It may be a pulse signal [3][4][5][6], a sinu-soidal signal [1,2,[7][8][9][10] or-easiest to implement and most commonly used-a rectangular signal [11,12]. Other signals that have been used include a pseudo-stochastic signal [13], a signal composed of the sum of sinusoidal waveforms with various appropriately selected frequencies and amplitudes [14], and a rectangular multifrequency binary sequence (MBS) signal [15].…”

Section: Main Approaches To the Thermal Time-of-flight Methodsmentioning

confidence: 99%

where v T is the temperature wave phase velocity (m/s), v is the gas velocity (m/s), ω is the wave frequency (rad/s), and κ is the gas temperature diffusivity (m 2 /s). From Equation (1), it follows that the velocity v T of the temperature wave is always greater than the drift velocity v and depends on the frequency of the wave.…”

Section: Methodsmentioning

confidence: 99%

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A Semi-Empirical Approach to Gas Flow Velocity Measurement by Means of the Thermal Time-of-Flight Method

Sobczyk

Rachalski

Wodziak

2021

Sensors

Self Cite

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This paper presents a method of measuring gas flow velocity based on the thermal time-of-flight method. The essence of the solution is an analysis of the time shift and the shape of voltage signals at the transmitter and at a temperature wave detector. The measurements used a probe composed of a wave transmitter and a detector, both in the form of thin tungsten wires. A rectangular signal was used at the wave transmitter. The time-of-flight of the wave was determined on the basis of the time shift of two selected characteristic points of the voltage waveform at the transmitter and the wave detector. To obtain the correct velocity indication, a correction in the form of a simple power function was applied. From the measurements performed, the relative uncertainty of the method was obtained, from approx. 4% of the measured value at an inflow velocity of 6.5 cm/s to 1% for an inflow velocity of 50 cm/s and higher.

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“…With the known hotwire driving frequency and comparing the sensing wire signal to the same, the spatial wavelength of the heat convection pattern was measured, and the air mean convection velocity was calculated. In recent years, quite a few excellent research works based on this concept have been published [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. In these studies, the approach was also named pulsed anemometers.…”

Section: Thermal Time-of-flight Sensingmentioning

confidence: 99%

Micromachined Thermal Time-of-Flight Flow Sensors and Their Applications

Huang¹

2022

Micromachines

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Micromachined thermal flow sensors on the market are primarily manufactured with the calorimetric sensing principle. The success has been in limited industries such as automotive, medical, and gas process control. Applications in some emerging and abrupt applications are hindered due to technical challenges. This paper reviews the current progress with micromachined devices based on the less popular thermal time-of-flight sensing technology: its theory, design of the micromachining process, control schemes, and applications. Thermal time-of-flight sensing could effectively solve some key technical hurdles that the calorimetric sensing approach has. It also offers fluidic property-independent data acquisition, multiparameter measurement, and the possibility for self-calibration. This technology may have a significant perspective on future development.

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High-precision anemometer with thermal wave

Cited by 12 publications

References 8 publications

Time-of-flight thermal flowrate sensor for lab-on-chip applications

Time-of-flight thermal flowrate sensor for lab-on-chip applications

A Semi-Empirical Approach to Gas Flow Velocity Measurement by Means of the Thermal Time-of-Flight Method

Micromachined Thermal Time-of-Flight Flow Sensors and Their Applications

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