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Pisetskiy Yuriy Valerevich, Tashkent University of Information Technologies, Docent, the Faculcy of Telecommunicetion E-mail: yuriy.pisetskiy@mail.ru
RADIO MONITORING OF THE ENVIRONMENT
Abstract: The article considers the issues of the necessity of environmental monitoring. The variants of the application of the radio monitoring system, a number of the main advantages of its use and the purpose of observations conducted within the framework of monitoring are given.
A structure for constructing a radio monitoring system is proposed. The working principle of the modernized thermo catalytic sensor is considered in order to increase its selectivity.
Keywords: Radio monitoring, ecology, environment, sensors, hazardous gases, selectivity.
Introduction In general, the listed main devices must perform all the func-
In some regions of our planet, world scientists develop specific tional tasks for the uninterrupted operation of the system: measure-programs for monitoring the ecological state of the geological envi- ment of physical quantities; Broadcasting of measurements on the ronment, monitoring the ecological state of surface waters, air and radio channel; Sensor control; Providing the user with a conve-
associated ecosystems. Such regions include the Central Asia with its unique geological environment and ecosystem that can easily be affected by anthropogenic influences [1].
The system of unified environmental monitoring provides for the development of mathematical models of industrial enterprises with various depths of study. The Simulation of the current situation allows to accurately identify focus of pollution and find adequate management at the interstate technological and economic levels [2].
Modern conditions ofwork at enterprises for processing mined gases or oil products require increased security measures. Therefore, the development of highly effective ways and means of continuous automated control of toxic and explosive components in the air is an actual problem. Safe operation of enterprises depend on the availability of such means of control which prevent emergency situations involving flammable substances release into the environment and provide effective work of warning systems.
At the moment there are many different ways to use the radio monitoring system, depending on the requirements of various industrial, household, strategic, or other objects [3]:
- System for collecting information on the status of elements and nodes of complicated mechanized systems;
- System for monitoring and collecting information on gas concentration;
- Pressure and flow monitoring system on the drainage area;
- Radio monitoring system for pumping station parameters;
- Radio monitoring and control of parameters of the filter station;
- System of remote gas control (the sensor is located in the selected area, collects, archives information on gas concentration, if necessary transfers data to a portable device, with a built-in radio module);
- Radio monitoring system for conveyor lines.
In all cases, the set of the radio monitoring system is a complex chain of interacting main devices, including: peripheral units containing radio modules, sensor modules equipped with the necessary sensors, a central control panel and information collection. Also, if additional services are needed, radio monitoring systems may include additional devices, depending on the requirements.
nient interface for collecting information from sensors and controlling sensors; Archiving of sensor information (if necessary); Work in data relay mode (if necessary).
Many enterprises today are still using wire monitoring systems, which, on the one hand, cheapens the control system for emissions of hazardous substances, on the other, makes it less reliable by the criterion of recoverability and non-mobile.
Most modern radiomonitoring systems are built on the basis of GSM networks. Such systems also do not always satisfy the reliability requirements, since in this case the exchange of information depends entirely on the radio channels of the cellular stations. Then the reliability of the system can be reduced by orders of magnitude, since the overall reliability ofthe system is the product of its own (circuit) and reliability of the cellular system servicing the monitoring system under consideration.
The use of the radio monitoring system has a number of main advantages [4]:
1. Increase the level of security due to the inability to intercept the signal from the radio sensor or simulate it;
2. The absence of cable jumpers allows to place sensors in hard-to-reach places to collect information;
3. In case of loss of general power at the object, the monitoring system continues to function and archive the received information;
4. Rapid deployment of the radio network.
Technique of experiments
The proposed developed radio monitoring system uses a radio channel in the civil band at a frequency of 27 MHz for transmitting information from the sensors to the central control panel, with a permissible output power of the transmitter up to 10W. The developed system is tuned to the transmitter power up to 1W, while the communication range between peripheral units and the central control panel is about one kilometer. The choice of range is due to the average size of the areas of the serviced enterprises. If necessary, it is possible to increase the power of the transmitters, which in turn will increase the communication range.
The system is designed for the fact that peripheral transmitters will be located in places where their power is possible only from batteries. Therefore, their work is configured discretely, i. e. In a certain
RADIO MONITORING OF THE ENVIRONMENT
time interval. The interval is selected for 20 minutes, and during these 20 minutes each transmitter operates for 10 seconds. By this method economical energy consumption of batteries is achieved [5].
To increase the noise immunity of the used radio channel and to provide reliable protection against industrial interference and unauthorized access to system data, signal transmission is performed digitally. To this, analog-digital and digital-to-analog converters have been introduced into the circuitry of the receiving and transmitting devices of the system being developed.
The prototype of the developed radio monitoring system consists of four peripheral units, which are installed in the places of necessary control of the environmental parameters and the central control panel, which serves information processing. The peripheral unit consists of a radio block (transceiver) and a sensor module, which includes a sensor producing the concentration of dangerous gases [4].
A sensor, or gas analyzer, in such monitoring systems is one of the main elements. An important metrological characteristic of gas analytical instruments is the selectivity index. Selectivity of the gas analyzer is the ability of measuring instruments from the composition of a complicated gas mixture to extract and fix the sought-for component with the maximum minimization of the effect on the final result of measurement of other, unmeasurable components included in the same gas mixture. That is, the effect of the unmetered components of the gas mixture on the result of the measurement of the sought-for component in its magnitude should be less than the specified maximum absolute error of the device. A means of measurement that satisfies this requirement is considered selective.
The transfer of thermochemical sensors from the function of detection and indication to the measurement function with observance of selectivity is a challenge in analytical instrumentation.
According to the conducted researches the technology of preparation of catalysts, providing selectivity for various ingredients, and also the technology of manufacturing the thermocatalytic sensors themselves, in which these catalysts are used, is proposed.
The principle of operation of the thermocatalytic sensor is based on measuring the concentration of the detected component from the gas mixture by the amount of heat released during the chemical reaction of catalytic oxidation. One of the methods used in the modernization of the thermocatalytic sensor to ensure its selectivity is to use its heat-sensitive elements containing catalysts having different degrees of activity to the components of the gas mixture. Sputtering of the thermosensitive elements of the experimental samples was carried out in a vacuum method with thermal magnetron evaporators, similar to the doping process described in [6; 7].
The work of the sensor, which provides the selectivity of determining CO in the presence of H2, is as follows. The analyzed gas mixture is fed to the sensing elements of the sensor. When the analyzed gas enters the catalyst, a complete oxidation of the mixture of carbon monoxide and hydrogen takes place. As a result, the output signal of one arm, the measuring element of the bridge circuit, is proportional to the total concentration of carbon monoxide and hydrogen, and the output signal of the other arm, the compensation element, is proportional to the concentration of hydrogen. The difference in the signal of the measuring and compensating elements is proportional to the exact concentration of carbon monoxide.
The sensor, in general, is a chamber in which a bridge circuit with two arms containing a measuring and compensation element is located. The principle ofoperation of the thermocatalytic sensor and the way to ensure selectivity is as follows. The analyzed gas mixture diffusively or forcedly enters the reaction chamber and enters into mechanical contact with the surface of the catalysts preheated by an electric current to the oxidation temperature of the sought-for component. Catalysts, multi-layered platinum helices and have varying degrees of activity. The catalyst, fitting the compensation element, has an inert activity with respect to the measured sought-for component.
Before the measurement, in the absence of the sought-for component, the bridge is in a balanced state, the output current is zero. When a sought-for component appears on the thermo catalytic sensor, the bridge emerges from the equilibrium state due to a change in the resistance of the measuring element and a current appears in the diagonal of the bridge, in proportion to the measured concentration of the sought-for component from the gas mixture. In this way, in a thermocatalytic sensor, a selective separation of the detectable component from a mixture of gases is simultaneously performed and its content is indicated.
Each of the gases has special chemical and specific physical properties: molecular weight, density, viscosity, specific electrical conductivity and thermal conductivity, ignition temperature, etc. As the main physical parameter, to ensure selectivity, the ignition temperature of combustible gases is chosen. For example : t (H2) = 580-590 oC; t (CO) = 644-658 °C; t (CH4) = 656-750 °C and so on.
Setting by the temperature on the measuring element of the thermo catalytic sensor corresponding to the ignition temperature of the sought-for gas, complete burning of the sought-for component from the composition of the combustible gases is carried out.
Thus, the process of implementing selectivity occurs in two, functional stages [8]. At the first, chemical stage, takes place chemical separation of gases. This is done by selecting the activity of various catalysts intended for thermocatalytic flameless oxidation corresponding to a group of combustible gases on a thermocatalytic sensor.
And in the second stage, physical, the selectivity is provided by additional afterburning on the same sensitive element. This is due to a specially set temperature for afterburning the sought-for component. The temperature is set by selecting the appropriate size of the current flowing through the measuring elements from the stabilized power source of the secondary device.
Experimental results and discussion
The developed device differs from its analogues in several basic features. In the radio modules of the system, digital-analog and analog-to-digital converters have been added. The circuit and algorithm of the control device are designed taking into account the digital signal transmission. And also taking into account discrete interrogation of peripheral devices. The central control panel includes the battery status indication.
The sensor module is designed in such a way that it is possible to replace the sensors with any other necessary for monitoring other chemical or physical parameters. This property gives universality to the developed monitoring system.
Thermocatalytic gas analyzers, having a miniature size, have another serious and important advantage over other existing
instruments based on other methods. The above procedure for increasing the selectivity of a thermocatalytic sensor is an advantage and has shown very good practical results in laboratory tests.
The final debugging of the developed system was carried out in the laboratory, after the completion of the assembly of all blocks of the system. Experimental tests of the developed radio monitoring system were carried out in real conditions at a gas processing station.
Conclusion
The creation of remote automatic radio monitoring of the maximum permissible and explosive gas concentrations, is one of the most important tasks of safety engineering and the solution ofvari-ous fire and environmental measures in many sectors of the economy.
The existing monitoring systems do not always meet the requirements of enterprises with specific conditions and regulations.
It is necessary to develop new systems that meet the requirements of enterprises and take into account the price policy in relation to the quality of the product.
The developed radio monitoring system takes into account the specific climate of Central Asia and the operating conditions for ensuring reliable, high-quality and autonomous work in the gas industry.
The upgraded thermo catalytic sensor showed positive experimental and practical results in the developed system of environmental radio monitoring. It can be used in other systems to determine the dangerous concentration of gases.
The proposed model of radio monitoring for the determination of hazardous gases has a wide range of applications in the oil and gas, chemical and other sectors of the economy, differing from the existing low cost, easy maintenance and high reliability indicators.
References:
1. Demina T. A. Ecology, nature management, environmental protection. - Moscow: Aspect Press, - 1998.
2. Ecology, nature protection and environmental safety. A manual for the system of advanced training and retraining of civil servants. Under the general editorship of prof. IN AND. Danilov-Danilyan. - Moscow: Publishing house MNEPU, - 1997.
3. Protasov V. F., Molchanov A. V. Ecology, health and nature management in Russia / Ed. V. F. Protasov. - Moscow: Finance and Statistics, - 1995.
4. Pisetsky Yu. V. Remote automatic radio monitoring. Report at the Republican Scientific and Technical Conference: Prospects for the Effective Development of Information Technologies and Telecommunication Systems. - Tashkent. PART 3. - March 13-14, - 2014. -P. 292-295.
5. Radzhabov T. D., Pichko S. V., Knyazev V. V., Sahibov Sh. D. Radiomonitoring of the gas content // Proceedings of the XVI Scientific-Technological Conf. "Vacuum science and technology". - Sochi, - 2007.
6. Radjabov T. D., Nazarov A. M., Koveshnikov S. V., Ibragimova B. B., Pisetskiy Yu. V. Application of ion doping to form a sensitive layer in a fiber-optic gaseous medium control sensor. Proceedings of XX Int. Conf. "Interaction of ions with a surface". Zvenigorod, Russia, -2011. - Vol. 2. - P. 133-136.
7. Radjabov T. D., Nazarov A. M., Davronbekov D. A., Piseckiy Yu. V., Gudkova N. I., Tadjieva A. Applying of the fiber laser for the humidity control in the cable water drain of the fiber-optical line. International Conference in Central Asia on Internet (ICI), - October 8-10, -2013. - Tashkent, Uzbekistan.Session 5: Optical Communications and Networking. 2013. IEEE.
8. Pisetskiy Yu. V., Talipov A. R. Analysis of qualitative indicators of the device for remote automatic radio monitoring of industrial enterprises. Republican scientific and technical conference "Key problems of technology and technology, their energy-saving and innovative solutions". Uzbekistan, Fergana, part 2. - April 20-22. - 2016. - P. 275-276.
