The analysis of gaseous media is an obligatory measure in the work of chemical plants, as well as in many industrial enterprises. Such studies are procedures for measuring a component in a gas mixture. For example, in mining enterprises, knowledge of the characteristics of the air in a mine is a matter of safety, and environmentalists thus determine the concentration of harmful elements. Not so often, such analyzes are used for domestic purposes, but if such a problem arises, it is best to use a gas analyzer. This is a measuring device that allows you to determine the composition of the gas mixture. At the same time, there are many varieties of this device that have fundamental differences.
Gas analyzer device
Despite the many structural variations of the device, there is a set of basic components that are present in each model. First of all, this is the case in which all the working elements of the gas analyzer are enclosed. The fact is that such devices require a high degree of protection, so serious requirements should be made to the outer shell. Almost every device requires power supply - accordingly, the battery can also be considered as a mandatory part of the device. Next, go to the more responsible component. This is a primary transducer, that is, a gas analyzer sensor or a sensing element that provides direct measurement data.
I must say that there are several types of such sensors, including thermocatalytic, infrared and electrochemical. The objective of this element is to convert the desired component of the gas composition into an electrical signal. After that, a measuring and indicating device comes into operation, which processes the given signal and demonstrates its indicators in the form of indication or display. Now it is worth considering the types of existing gas analyzers.
Thermochemical models
In devices of this type, the principle of measurement is provided by determining the thermal effect of a chemical reaction involving the desired component. As a rule, in the process of work, the oxygen oxidation technique is used. Therefore, such a device can be considered as an oxygen gas analyzer, and hopcalite, which is deposited on a porous carrier, performs the function of catalysts. Oxidation is measured using metal or semiconductor thermistors. In some cases, the surface of platinum thermistors also acts as a catalyst. Typically, thermochemical models are used to work with combustible gases and vapors, as well as in the process of electrolysis of water. With its help it is possible to determine, for example, the oxygen content in hydrogen.
Magnetic devices
In this case, we are also talking about devices focused on the determination of oxygen. A gas analyzer of this type monitors the susceptibility of the magnets relative to the medium under study, depending on the concentration of oxygen in it. It would seem that this component can be determined by other varieties of the device, but there is one feature. The fact is that a magnetic gas analyzer is a meter that is able to more accurately determine the concentration in complex mixtures. You should also distinguish between magnetomechanical and thermomagnetic devices. In the first case, the device measures the force acting in an inhomogeneous magnetic field on a sensitive element located in the medium under study, for example, a rotor. Indications will depend on the temperature of the medium and pressure. The principle of operation of thermomagnetic models is based on the convention that occurs when a gas mixture interacts with inhomogeneous temperature and magnetic fields.
Pneumatic models
Such devices work on the basis of measuring viscosity and density. For this, the data of the hydromechanical properties of the flow are analyzed. I must say right away that there are three options for such devices: throttle, inkjet and pneumatic acoustic. The throttle gas analyzer is a device with a converter that measures the hydraulic resistance when a gas mixture passes through itself. Jet models measure the dynamic characteristics of the pressure of a gas mixture flowing out of a nozzle. Typically, devices of this type are used in work with nitrogen and chloride compounds.
The pneumatic-acoustic device includes two whistles with approximately equal frequencies of the order of 4 kHz. The first whistle passes the analyzed gas through itself, and the second - the composition for comparison. As a result, an air gas analyzer allows you to compare vibration frequencies, converting the indicators into pneumatic vibrations using an amplifier. To provide a signal, a frequency-analog type converter is used.
Infrared models
The principle of operation of such gas analyzers is based on the selective absorption of vapor and gas molecules by infrared radiation. It is important to consider that the device provides for the absorption of those gas mixtures whose molecules contain at least two different atoms. The specificity of molecular spectra in various gases determines the increased selectivity of such devices. For example, there are conventional and dispersion versions of the converter. A dispersive gas analyzer is a device that uses radiation generated by monochromators, that is, diffraction gratings or prisms. In ordinary representatives of this class, nonmonochromatic radiation is used, which is provided due to the features of optical schemes. For this, filters, special radiation detectors and other components are used. Also, non-selective type radiation detectors can be used in infrared gas analyzers - in particular, thermal batteries, bolometers and semiconductor components.
How to use the device?
It is important for the user of the device to familiarize themselves with the display or other device for displaying information that is supplied with the device. As a rule, modern displays display the date, as well as several fields for data on the composition of the gas mixture. Obtain complete information about the value of the fields and channels of the device will allow the instructions of the gas analyzer in a specific configuration. Actually, the control of instrument functions also depends on the specific model. As a rule, it is enough to activate the device while in the gas environment. Further, when the threshold concentration indicators of the desired component are reached, the device will give a signal. In some models, light indication is also possible. At the same time, the main lines on the chemical composition of the gas mixture and the properties of the specific component that the device was configured on should be filled in on the screen of the device.
Device verification
Like any measuring device, the gas analyzer needs verification. This procedure will allow you to evaluate the technical condition, performance of the device, as well as its compliance with metrological characteristics. Most often, portable gas analyzers are subject to failures in operating indicators, therefore, their maintenance should be done more often. So how is verification done? The procedure is performed on a special calibration bench. It begins with an inspection of the device, testing the replacement of faulty elements. This is followed by calibration measures and the necessary settings.
Direct verification involves the use of a device to assess the concentration of a particular component in a compressed gas cylinder. That is, special mixtures are used, with the help of which gas analyzers are checked for the analysis of a specific component.
Gas analyzer reviews
As the practice of operating such devices in enterprises shows, the models of a domestic manufacturer are practically not inferior in quality to their foreign counterparts. You can focus on the products of firms "Testo", "Ditangaz", "Giam", etc. In the model lines of these companies you can find high-quality stationary and portable gas analyzers for working with various mixtures. However, users note that the weak point of almost all devices of this type is a sensitive element, that is, a sensor. Therefore, you should consider in advance the possibility of maintenance with the replacement of this component.
How much is a gas analyzer?
The initial level is represented by models at the price of 3-5 thousand rubles. For this amount, the owner receives a device equipped with a digital display and a semiconductor sensor. Other parameters, such as sensitivity, response time and probe parameters, are unlikely to be of interest to a specialist. If you need a device for responsible work with combustible and explosive substances, then you should focus on a professional gas analyzer. The price in this case can be about 30-40 thousand rubles, but a qualitative result will be ensured. In addition, for the money you can count on the versatility of the gas analyzer and a high degree of ergonomics.
Conclusion
Measuring devices are quite widely represented on the market, however, gas instruments belong to a specific segment. On the one hand, this makes it difficult to find a suitable device, on the other hand, it allows you to get acquainted with the assortment in more detail. If we talk about universal selection rules, then you should not buy a gas analyzer, the price of which does not exceed 5 thousand rubles. Such devices, although they provide a basic set of options and guarantee a certain level of accuracy, are not always distinguished by their durability and require frequent verification. Also, when choosing, it is worth considering the possibility of operating in different conditions. For example, most of these devices are sensitive not only to the chemical composition of gas mixtures, but also to temperature.