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control all drying system by changing temperature control program parameters and heating load capacity such as clothes drying system, fruit drying system. References
1. Luu The Vinh (2002). Textbook of Electrical and Electronic Measurement Techniques. Dalat University. [in Vietnamese language]
2. Nguyen Huu Cuong. (2007). Sensor technology. Can Tho University. [in Vietnamese language]
3. https://www.haoyuelectronics.com/Attachment/AM2301/AM2301.pdf
© Mac B.V., Nguyen H.T., Tong H.T., Nguyen H.N., 2024
УДК 62
Mac Van Bien, Le Oinh Giang, Nguyen Van Tung, Tran Ngoc Quang
Faculty of Electronics and Informatics, College of Industrial Techniques (CIT), Bac Giang City, Vietnam
OPTOELECTRONIC SYSTEM FOR MONITORING SMOKE DENSITY DURING SAMPLE COMBUSTION IN A CHAMBER
Abstract
The article considers an optoelectronic system for monitoring smoke density during sample combustion in a chamber. This device contains a system of mirrors to increase the source beam path, which increases the sensitivity of smoke density measurement, and a source modulator, which reduces the noise level and background influence.
Keywords:
smoke emission, photometry, smoke density measurement, optical-electronic system.
Currently, in various areas of human activity, there is a problem of monitoring the smoke content of the environment. The existing devices for monitoring the smoke content of the environment implement the principle of measuring the smoke density during object combustion. To improve the accuracy of measurement, the authors propose to use modulation of the source radiation flux, an optical system of the radiation flux length in the chamber, and a gain correction unit of the optoelectronic path.
The thermal noise voltage dispersion is determined by the Nyquist formula [1]:
VT.N. = 4kTRAf, (1)
where k = 1,38 • 10-23 J • K-1 is Boltzmann constant, T is the ambient temperature, R is the photoresistor resistance, Af is frequency band in which measurements are taken.
Shot noise is explained by the fact that electric current is a flow of particles that fluctuate in time. Flowing through the load resistance RL, the shot noise current creates a noise voltage[1, 3]:
Vs2n. = 2eIoR2lAf, (2)
Generation-recombination noise is caused by the random nature of the generation of current carriers, as well as the random nature of the recombination of these carriers. The dispersion of the generation-recombination noise voltage for photoresistors[1, 3]:
v2 = 4v2. rlrt t"m—1— (3)
Current noise combines several types of noise that are difficult to calculate separately. It depends on the
surface condition and manufacturing technology of the photosensitive layer, on the quality of contacts and leakage currents. Dispersion of the voltage of current noise on the load resistance RL [1, 3]
(4)
Vc2.n. = br2llo2f ,
The signal at the output of the photocurrent amplifier is determined by the ratio:
u(t) = SiRlxpKyO(t), (5)
Since the measurement error is a random function, then in the absence of a correlation relationship between the parameters and the same distribution laws of the measurement results, the error is determined by the following expression [2, 3]
6u= j62l + 6rl + 62 + 62p + 6ky + 6|.
(6)
Figure 1 - Schematic diagram of the test device for measuring smoke density under specified conditions
Fig. 1 shows a diagram of an optoelectronic system for monitoring smoke density during sample combustion in a chamber (top view): 1 - test chamber; 2 - fan; 3 - damper and air screen; 4 - support; 5 -combustion of sample; 6 - light source; 7 - optical system; 8 - disk modulator; 9 - mirrors; 10 - light guide; 11 -equipped with a movement mechanism; 12 - computer; 13 - screen.
Conclusions. The introduction of a modulated optical flow and a selective scheme for its registration allows us to reduce the effects of noise, eliminate the effects of background illumination and zero drift of the photodetector in optical system 7, and the introduction of a system of mirrors allows us to increase the sensitivity of the measurement method by increasing the length of the optical beam and to reduce the effects of uneven smoke in the test chamber on the control error. All these introductions allow us to increase the accuracy of control, and the system of mirrors allows us to reduce the dimensions of the chamber. In addition, the modulation of the radiation flow will significantly simplify the design of smoke meters in pipes, since the proposed version eliminates the effect of background illumination. References
1. G. G. Ishanin [et al.]. (2003). Radiation receivers. St. Petersburg: Papyrus. [in Russian language]
2. P. V. Novitsky, I. A. Zograf. (1991). Estimation of errors in measurement results. Leningrad: Energoatomizdat. [in Russian language]
3. Shilin A. N., Borbenchuk A. S., Kotsur D. I. Opto-electronic monitoring system of smoke density of electric cables burning chamber // Bulletin of the Volgograd State Technical University. - 2015. - №.11. - P. 79-83. [in Russian language]
© Mac B.V., Le G.D., Nguyen T.V., Tran Q.N., 2024
