Vladimir Gryuk

Faculty of Computer Information Technologies and Automation(CITA)

Department of Electronic Technology

Speciality Electronic Systems

Development of an electronic system for calibration and research anemometer

Scientific adviser: Ph. D. Dmitry Kuznetsov

Resume Abstract

Abstract

Content

• Introduction
• 1. Relevant topics
• 2. Purpose and objectives of the research
• 3. Overview of Research and Development
• 4. Current outcome
• Conclusion
• List of sources

List of sources

Thermoanemometers (TA) have been widely used for measuring gas flow velocities. They have high sensitivity in a wide range of measured speed, easy to manufacture, do not contain expensive elements, and have an electrical output without requiring additional amplification. In particular, TA successfully used:

• to control speeds and ventilation costs flows during the construction of various architectural structures and during their operation;
• to conduct research on study of the dynamic parameters of turbulent flows;
• measurement concentration of flammable gases;
• in the automotive industry to optimize of gasoline internal combustion engines;
• the study flow control and complex bodies of gas flows;
• flow Measurement gases in large pipes, etc. [1].

1. Relevant topics

Currently, the actual is the problem of measuring airflow in accounting systems consumption, and environmental monitoring systems in industrial ventilation. Air flow in industrial and ventilation ducts has predominantly turbulent, chaotic character and three-dimensional structure; is essential dynamic, pulsating velocity component. This imposes more stringent and high metrological requirements and performance air velocity meters.

In this context emerged the need to develop technical means to experimentally determine the static and dynamic characteristics speed sensors and assess the impact on the metrological characteristics measurement conditions, design features and materials transducers. The analysis showed that one of the few devices to meet the requirements of the Drugs measuring the characteristics of turbulent flows is  anemometer. Sensor element TA substantially does not disturb the flow, low inertia and does not depend on changes in ambient temperature [2].

2. Purpose and objectives of the research

The aim is to development and research-flight anemometer, as well as an assessment of its metrolagicheskih characteristics.  For achieve this goal in the makes the following main problem :

1. Overview methods and means of measurements of the local velocity and temperature of gas flows.
2. Development of  anemometer, whose testimony will be invariant to changes Temperature of the gas flow.
3. Static anemometer calibration.
4. Dynamic evaluation anemometer characteristics.
5. Rationale for structural design of the electrical system of the signal recording anemometer.

3. Overview of Research and Development

Question opredileniya speed gas streams and explore widely in many razrabatyvaetsya developed countries such as:

• Russia (Scientific-Production Association Turbulence-DON);
• Canada (company TransKanada Pipelines);
• and excluding Ukraine became (LLC "DP Ukrgazteh" и and special Design and Technology Bureau «Turbulence» Donetsk National University).

These research centers and industrial companies on spetsializiruyutsya solving a number of practical problems in industry, ecology, occupational safety and health. For this it is necessary to determine the dynamic and velocimeters thermal characteristics and temperature air flows. This parameter control systems and ventilation air conditioning, climate in residential and industrial buildings, cockpits and interiors of vehicles, fume collection channels and pipes.

The instruments used for these measurements must possess a wide range, as the speed (as tenths to several tens of meters per second), and by temperature (from tenths to several hundred degrees), high sensitivity at low pressure drops (Pascal units). They must be reliable and easy to use, provide an indication parameter being measured in units of physical quantities. These requirements are fully meet modern thermoanemometers.

The Special Design and Technology Bureau «Turbulence» Donetsk National University developed and produced several modifications such thermoanemometric devices:

- Anemometer AIST-5. Autonomous measuring the velocity and temperature of the air flow;

- Thermoanemometer IRIT-4. Flow Indicator and traction;

- Thermoanemometer ISRV-2. Hot-film gas flowmeter [3].

4. Current outcome

Main scope anemometer is small opredilenie skorostyaey air flows. This is due to the fact that other anemometers in the art can not give unambiguous testimony that would not depend on changes the temperature of the stream.

Sensor developed TA consists of two parallel tungsten wires diameter 5 mm and length 5 mm, arranged perpendicularly to the flow gas at a distance L = 3 mm apart (see Fig. 1).

The first wire Rt1 pulses are applied voltage, and it emits thermal labels that carried by the gas stream and recorded by means of a second wire Rt2. By the time lag τ second signal wire relative to first determine the rate flow.

At the same time on propagation of thermal labels are not affected by the temperature and flow component composition. That is TA readings will invariant to changes in temperature and composition of the flux.

Circuitry ТА. functional diagram developed TA is shown in Figure 2. Module microcontroller (MC) generates a signal given shape and heating frequency , which, through digital to analog converter DAC and amplifier PA power is supplied to the first wire Rt1 TA sensor . heat tags displaced by the flow and recorded the second wire Rt2, which is incorporated in a measuring bridge thermometer. measurement signal is amplified by the differential amplifier and the control unit via an analog-to-digital converter input to the MC. Accumulated as a result of measurement data sets transmitted to a personal computer for DSP [4].

prototype TA implements the algorithm described above operation was made using the Module Arduino Uno microcontroller based ATmega328. The composition of this MK includes 10-bit ADC, but no built-in DAC. The simplest DAC has been implemented based on an 8-bit pulse-width modulator (PWM) with the addition of PWM output RClow-pass filter of the first order [5].

As the original signal heating used a sinusoidal voltage with a frequency of 200 Hz amplitude and offset of 0,5 V. The sampling frequency was chosen to be 8 kHz.

Experimental graduation ТА conducted ADS-200/250 aerodynamic stand speeds ranging from 1 to 4 m/s air stream at temperatures of 25 and 40 C. At each point on the speed check carried out the original signal and the heating power received signal. The type species of these signals is shown in Figure 3. From results show that the received signal is disturbed by noise and phase shifted relative to the original signal [6].

Arrays of measurement data accumulated and processed in computer. To determine the time delay of the received signal correlation was calculated relative to the original signal.

where n — sample size (10000 points); xi и yi — arrays of discrete values source and received signals, respectively; k — mutual displacement signals.

Correlation (2) was calculated at various displacements k, constructed correlation function (see Fig. 4) and determined offset kmax, corresponding to the maximum correlation function [7], [8].

Elaboration flow rate determination function. With by experimental data found that with increasing flow rate delay τ not seek to 0, and to a certain value τ(∞). This is explained by the influence of the inertia sensor and measurement chains TA.

Conclusion

1. In the course of the work was the proposed equation (3) calibration characteristics developed TA which provides an approximation of the experimental data with the calibration relative error of the speed is not more ± 2 %.
2. The experimental calibration results identified the main metrological anemometer characteristics and the requirements to the ADC circuit signal processing.
3. Indications TA invariant to changes in the temperature of the gas flow, which allows perform his grading at an arbitrary temperature.
4. At writing this essay Master's work is not yet complete. Final completion: December 2014. Full text of the work and materials on the topic can be obtained the author or his manager after that date.

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