The device for measurement of saltationing grains’ parameters

Аuthors

Lisutenko A. S.^*, Mirsaitov S. F.^**, Titov A. A.^***

Moscow State University of Engineering and Computer Science, 20, Stromynka str., Moscow, 107996, Russia

*e-mail: Lisyutenko_AS@mgupi.ru
**e-mail: mgupipr5@mail.ru
***e-mail: dor7338@mail.ru

Abstract

It is proposed the device for measuring of saltationing grains’ parameters with an upgraded optical system and based on a combination of the interference method and the method of light scattering by particles, crossing the laser beam.

The proposed device consist of a laser, illuminated an acoustic-optic modulator (AOM), which is served voltage of high and low frequency from the control unit, two measuring channels with upgraded optics.

Laser module illuminates the AOM by an advanced beam, which is served voltages of the two closely located frequencies from the control unit, which allows us to create a interference pattern in the diffracted beam. At the output of the first AOM beams of the first and zero order are standed out. Grains are introduced into the measurement volume with the tube. When grains fly out through two beams, light is scattered on them and enters two measuring channels. The first channel is formed by a lens, photodetected module, phase detector and a frequency control unit, and the second — lens, photodetected module and a digital oscilloscope.

When grains fly out through the interference pattern in the first channel, light, scattered on it, will acquire the Doppler frequency shift, which is proportional to the grain’s speed with flying through measuring volume.

The second measuring channel allows to estimate the size of the saltation grain, using the amplitude and the shape of the pulse signal from the outputs of the photodetected module.

As a result of researching for the first channel we get that photodetector`s minimal detected power is 2,74*10^-11 W. The signal-to-noise ratio is 26.37. And it is sufficiently for reliable reproduction of information.

For the second channel photodetector`s minimal detected power is 3,55*10^-13 W. The signal-to-noise ratio is 253.5.

Accuracy of velocity measurement is about 5%.

The relative error in measuring the size is 0.86%.

Studies have shown, that using of proposed upgraded optical system of the device may extend the range of measurement saltation particles’parameters.

Keywords:

laser module, optical-acoustic modulator, photodetector, lens, frequency meter, phase detector, digital oscillograph

References

1. Titov A.A., Gorchakov G.I., Buntov D.V. Doklady Akademii Nauk. Geofizika, 2009, vol. 424, no.1, pp.102-106.

2. Titov A.A., Mirsaitov S.F. Metrologiya, 2013, no.1, pp. 18-23.

3. Titov A.A., Amurskij V.V., Garipov V.K. Metody postroeniya i rascheta lazernykh izmeritel’nykh i zapominayushchikh ustroistv (Methods of construction and calculation of laser measuring and storage devices), Moscow, Mashinostroenie, 2008, 134 p.

4. Titov A.A. Izmeritel’naya tekhnika, 2008, no.11, pp. 43-45.

5. Zakaznov N.P., Kirjushin S.I., Kuzichev V.I. Teoriya opticheskikh system (The theory of optical systems), Moscow, Mashinostroenie, 1992, 447 p.

6. Dubnishhev Ju.N., Rinkevichjus B.S. Metody lazernoi doplerovskoi anemometrii (Methods of laser Doppler anemometry), Moscow, Nauka, 1982, 304 p.

7. Yaping Shao. Physics and Modelling of Wind Erosion, Springer, 2008, 452 p.

Download