Analysis of gas media is a mandatory activity in the work of chemical industries, as well as in many industrial enterprises. Such studies are procedures for measuring a particular component in a gas mixture. For example, in mining enterprises, knowledge of the characteristics of the air in the mine is a safety issue, and environmentalists thus determine the concentration of harmful elements. Not so often, such analyzes are used for domestic purposes, but if such a task arises, then 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, which have fundamental differences.
Gas analyzer device
Despite the many design variations of the device, there is a set of basic components that are present in each model. First of all, this is a housing that contains all the working elements of the gas analyzer. 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 - respectively, the batterycan also be considered as a mandatory part of the device. Next, it is worth moving on to a more responsible component. This is a primary transducer, i.e. a gas analyzer sensor or sensing element that provides direct data for measurement.
I must say that there are several types of such sensors, including thermal catalytic, infrared and electrochemical. The task of this element is to convert the desired component of the gas composition into an electrical signal. After that, the measuring and indicating device comes into operation, which processes this signal and demonstrates its indicators in the form of an indication or display on the 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, the oxygen oxidation technique is used in the process. 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. Measurement of oxidation indicators is carried out using metal or semiconductor thermistors. In some cases, the surface of the 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 water electrolysis. It can be used to determine, for example,oxygen content in hydrogen.
Magnetic devices
In this case, we are also talking about devices focused on the determination of oxygen. This type of gas analyzer monitors the susceptibility of 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 types of the device, but there is one feature. The fact is that a magnetic gas analyzer is a meter that is able to determine the concentration in complex mixtures with higher accuracy. It is also necessary to 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 placed in the medium under study, for example, a rotor. Readings will depend on medium temperature and pressure. The principle of operation of thermomagnetic models is based on the convention that occurs when a gas mixture interacts with non-uniform temperature and magnetic fields.
Pneumatic Models
Such devices work on the basis of measuring viscosity and density. To do this, the data of the hydromechanical properties of the flow are analyzed. It must be said right away that there are three options for such devices: throttle, jet and pneumoacoustic. A throttle gas analyzer is a device with a transducer that measures the hydraulic resistance when a gas mixture is passed through it. Jet type models measure the dynamic characteristics of the pressure of the gas mixture,flowing from the nozzle. Usually devices of this type are used in work with nitrogen and chloride compounds.
The pneumoacoustic device includes two whistles with approximately equal frequencies of about 4 kHz. The first whistle passes the analyzed gas through itself, and the second - the composition for comparison. As a result, the air gas analyzer allows you to compare the oscillation frequencies, converting the indicators into pneumatic vibrations using an amplifier. A frequency-to-analogue type converter is used to provide the signal.
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 also determines the increased selectivity of such devices. For example, there are conventional and dispersion versions of the transducer. A dispersive gas analyzer is a device that uses radiation produced by monochromators, that is, diffraction gratings or prisms. In ordinary representatives of this class, non-monochromatic radiation is used, which is provided due to the features of optical circuits. For this, light filters, special radiation receivers and other components are used. Also, non-selective type radiation detectors can be used in infrared gas analyzers - in particular, thermopiles, bolometers andsemiconductor components.
How to use the appliance?
It is important for the user of the device to become familiar with the display or other output device that the device is equipped with. As a rule, modern displays show the date, as well as several fields for data on the composition of the gas mixture. To obtain complete information about the meaning of the fields and channels of the device, the instruction of the gas analyzer in a specific configuration will allow. Actually, the control of the device functions also depends on the specific model. As a rule, it is enough to activate the device while in a gaseous environment. Further, when the threshold concentrations of the desired component are reached, the device will give a signal. In some models, a light indication is also possible. At the same moment, the main lines about the chemical composition of the gas mixture and the properties of a certain component to which the device was tuned should be filled in on the screen of the device.
Check device
Like any measuring device, the gas analyzer needs to be calibrated. This procedure will allow you to assess the technical condition, performance of the device, as well as its compliance with the metrological characteristics. Portable gas monitors are the most likely to experience performance failures, so they need to be serviced more frequently. So how is verification done? The procedure is performed on a special calibration stand. It begins with an inspection of the device, testing the replacement of faulty elements. The following are calibration measures and the implementationnecessary settings.
Direct verification involves the use of a device to assess the concentration of a particular component in a cylinder of compressed gas. That is, special mixtures are used, with the help of which gas analyzers are calibrated for the analysis of a particular component.
Reviews on gas analyzers
As the practice of operating such devices at enterprises shows, models of a domestic manufacturer are practically not inferior in quality to imported counterparts. You can focus on the products of Testo, Ditangas, 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 the sensitive element, that is, the sensor. Therefore, the possibility of maintenance with the replacement of this component should be considered in advance.
How much does a gas analyzer cost?
The initial level is represented by models priced at 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 high-qualityresult. In addition, for this 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, but devices for working with gas 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 the universal rules of choice, then you should not purchase a gas analyzer, the price of which does not exceed 5 thousand rubles. Although such instruments provide a basic set of options and guarantee a certain level of accuracy, they are not always durable and require frequent verification. Also, when choosing, it is worth considering the possibility of operation in different conditions. For example, most of these devices are sensitive not only to the chemical composition of gas mixtures, but also to temperature.
