Review of modern gas analyzers and their properties

At any public utility facilities, in industrial production, in mines and even in homes, there may be an increased risk of poisoning with harmful gaseous substances. This situation is quite common, so it is necessary to constantly monitor the quality of the air people inhale and check for the presence of harmful gases in it.

More recently, people used various home-made structures for the above places, allowing them to determine the presence of dangerous gas mixtures. In the modern world, circumstances have seriously changed and special analyzers have begun to be used everywhere, which in the shortest possible time are able to determine the presence of harmful substances in the air and send a corresponding signal to a person about this.

Gas analyzer device

Almost all such devices have three key elements in their design - a detector (transducer), a measuring part and a power source. Regarding the detector, it can be conventionally represented as an ultra-sensitive module capable of determining the presence/absence of certain vapors in the air mixture, about which a corresponding signal is given to the operator. This sensor can be based on different operating principles, depending on the method of fixation of the chemical substance. The signal processing itself is performed by the measurement module. Thanks to it, household apartment gas analyzers are able not only to register the presence of a particular substance, but also to reflect its specific value visually (for example, display a numerical value on the display). And if we talk about the latest models of the devices in question, they can decompose the analyzed substance into its component parts and display each specific value.

To carry out continuous/autonomous operation, the devices are designed with different power sources. These can be AA and AAA batteries, rechargeable batteries, or they can be powered from an electrical network. Thus, there are both portable and stationary models.

How to choose a gas analyzer

When purchasing a device, you first need to determine its purpose: what substance it should detect and under what conditions.

After this, we recommend determining the form factor of the equipment. If you need a gas analyzer to constantly monitor the air in one room, choose a stationary model.

Mobile or portable equipment is used when frequently moving from one workplace to another.

The third important factor is the accuracy of the definition. For some gases, a change in concentration of 0.01% is already critical. The device must quickly detect such fluctuations and notify the user about it.

Using the device to analyze gas mixtures

The devices under consideration are high-tech and high-precision measuring equipment, intended for the analysis of components entering the atmospheric air, and also capable of determining the qualitative and quantitative composition of gas mixtures. The devices are equipped with special sensors that detect excess levels of hazardous components in the air. As a rule, for the full operation of these devices, auxiliary equipment is also required, which, for example, will create the necessary pressure (compressors), and if harmful substances are detected, it will begin to automatically clean the air from tar, dust, etc.

Using gas analysis instruments it is possible to perform:

Environmental air control, i.e. monitor the atmosphere to prevent man-made disasters and promptly respond to the fact of their occurrence (for example, determining the increase in the concentration of dangerous carbon dioxide or other harmful substances).
Monitor the current atmosphere in the work area, maintaining the occupational health and safety system. This is especially true for large garages, boiler rooms, deep wells, as well as in tunnels and other underground objects. They are intended not only to determine the presence of harmful substances, but at the same time are aimed at eliminating their influence (for example, automatically turning on ventilation).
Monitoring of industrial emissions during technological processes at energy, metallurgy, petrochemical and cement industry facilities. However, in these industries it is necessary to know the permissible harmful composition of the gas environment and regularly obtain measurements of the content of hydrogen, oxygen, methane, sulfur, nitrogen, etc. Industrial analyzers are considered the most powerful because they can monitor up to 50 different components simultaneously.
Analysis of the operation of gas turbines, furnaces and burners, as well as boilers - any equipment that uses a fuel combustion mechanism.
Identify gas leaks when installing a gas pipeline or waterproofing a pipeline.
Determine the concentration of gas in a liquid, which is necessary for water purification procedures. Typically, for these purposes, a method of analyzing oxygen and its partial pressure is used to find out its total content in the liquid. Area of use: aeration and wastewater treatment stations, water quality control laboratories.
Analysis of vehicle exhaust gases in the field of auto diagnostics. Such equipment is capable of measuring 4 component gas mixtures - O2, NOx, CH, CO2. From here the toxicity of the exhaust will be calculated and, accordingly, it will be possible to determine the general condition of the car, find out problems and malfunctions of the internal combustion engine, as well as the ignition and fuel circulation systems;
Monitoring the quality of the atmosphere in a residential area - helps to identify sources of leakage at the household level;
Monitoring the alcohol vapor exhaled by a person will help determine the level of alcohol in the blood.

Types of gas analyzers

A variety of gas analyzers based on physical characteristics of operation. Today, there are more than 10 types of gas analyzers, which are divided according to the physical characteristics of analyzing the gas environment.

But there is no such universal design for measuring the composition of impurities. For some, a certain physical principle is suitable, but for others it will be unacceptable.

By the way, read this article too: Equipment Corrosion

Thermoconductometric

May react to the thermal conductivity of mixtures. It analyzes how effectively temperature is transmitted in a gas environment. This device is suitable only if the thermal conductivity of impurities and gases differs significantly from each other.

Pneumatic

Designed to determine the viscosity of the mixture, which is inherent in a given room. They are also used in explosive objects, since they do not have an electrical component. There is no spark, therefore the gas will not ignite.

Magnetic

It is suitable for oxygen analysis. These devices are used in those mechanisms where the gas mixture is to be burned. Example of an indicator: lambda sun. It is found in the exhaust system of cars, which are now relevant in the modern car market. Designed to determine the oxygen concentration in relation to the exhaust gas output. It also serves to determine how well the automobile fuel has warmed up. Infrared

Needed to irradiate a gas environment with infrared rays. They have a built-in explosion-proof housing, as they are used where there are explosive substances. It is used for laboratories and industry.

Ionization

Checks for electrical conductivity. If there are impurities in the composition, then the electrical conductivity is different. This is recorded and reflected as a percentage on the scoreboard. It is intended for gases that are not flammable.

Ultraviolet

They have the same principle as infrared. But there is a difference in that they are irradiated with ultraviolet rays. These devices can analyze the absorption intensity of the medium using rays that are directed at them.

Luminescent

Necessary in order to determine which gases have luminescent properties. They depend on the concentration of these impurities. This is a rare type of device because it is the most complex type. In practice, as a rule, simpler technologies are used. There are other equipment that have different physical principles. It is the most expensive and requires complex maintenance. Equipment based on chemical principles is charged with certain chemical reagents. They are used if there are specific gases for which other methods are not suitable.

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Classification of gas analyzers

The devices discussed in this article have many modifications and can be classified into several categories at once.

By functionality:

Indicator - they are capable of giving a qualitative assessment of a gas substance based on the presence of a substance subject to control. The data will be displayed with several dot indicators. When all indicators are fully lit, this means that there are too many controlled components, and when one or two are present, this means a normal level. Leak detectors can also be included in this group - they are equipped with special probes (or samplers), thanks to which the location of a leak in the pipeline is detected.
Signaling - they have one or more threshold signals. Their optical indicator elements are triggered visually or with sound when the concentration of a harmful mixture reaches a threshold value.
Gas analyzers themselves - they are adapted to provide an estimate of the concentration of a gas mixture based on its mass or volume. Usually they are also supplemented with threshold equipment equipped with a digital/analog signal or even a printer.

By design features:

Stationary samples are large and massive, they are designed for uninterrupted operation. They are used to monitor the working area of an industrial enterprise and record the degree of gas contamination both in the room itself and in the environment. This equipment is aimed at studying the concentration of gases, and in particular their maximum permissible values. They have integrated threshold sensors, which, when there is a threat of exceeding gas pollution limits, turn on the siren, start automatic ventilation, and close a special shut-off valve.
Portable samples are slightly smaller devices that are easy to transport from one facility to another and are quite simple to start in operating mode. They are used in the oil and gas industry, utility industries, as well as during environmental monitoring and laboratory research. In most cases, they are used by the Ministry of Emergency Situations, sanitary supervision, as well as companies for the installation and adjustment of air conditioning, ventilation and heating systems. Some models are used in civil engineering by industrial safety and labor protection departments of organizations.
Portable samples - they are compact and lightweight. They are used in the production, transportation, processing of oil and gas, as well as in water utilities, tunnels and wells. They can be found at gas stations and other places where it is necessary to ensure the personal safety of employees. They are also used by ecologists during field work during monitoring of air composition in residential areas or industrial enterprises. These devices are equipped with visual and audio alarms and can be supplemented with an infrared port (or other modules for wireless data transmission) in order to send results to the “mother” station.

Separately, it is worth mentioning smoke gas analyzers - they are designed to monitor the optimization of combustion processes, while simultaneously making an inventory of emissions produced into the atmosphere. Used in rooms with industrial furnaces and boiler rooms. They are also able to detect the amount of carbon monoxide in a confined space, or determine the location of gas leaks.

By the number of measured components:

Industrial narrowly focused ones (in a specific industry) are usually adapted to identify only one or two components;
Automotive – mandatory four (but may be more);
Professional laboratory models can determine up to 50 components.

Types of gas analyzers

March 18, 2013
GAS ANALYZERS, devices that measure the content (concentration) of one or more. components in gas mixtures (see also Gas analysis). Each gas analyzer is designed to measure the concentration of only certain components against the background of a specific gas mixture at normal levels. conditions. Along with the use of individual gas analyzers, gas monitoring systems are being created that combine dozens of such devices. In most cases, the operation of a gas analyzer is impossible without a number of auxiliary equipment. devices that ensure the creation of the necessary temperatures and pressures, purification of the gas mixture from dust and resins, and in some cases from certain components and aggressive substances that interfere with measurements. Gas analyzers are classified according to the principle of operation into pneumatic, magnetic, electrochemical, semiconductor, etc. The physical ones are outlined below. fundamentals and areas of application Naib. common gas analyzers.

Thermoconductometric gas analyzers. Their action is based on the dependence of the thermal conductivity of the gas mixture on its composition. For most practically important cases the following equation is true:

where is the thermal conductivity of the mixture, is the thermal conductivity of the i component, Ci is its concentration, n is the number of components.

Thermoconductometric gas analyzers do not have high selectivity and are used if the controlled component in thermal conductivity differs significantly from the rest, for example. for determining the concentrations of H2, He, Ar, CO2 in gas mixtures containing N2, O2, etc. The measurement range is from units to tens of percent by volume.

A change in the composition of the gas mixture leads to a change in its thermal conductivity and, as a consequence, temperature and electrical properties. resistance of metal heated by current. or a semiconductor thermistor placed in a chamber through which the mixture is passed. Wherein:

where a is the design parameter of the chamber, R1 and R2 are the resistance of the thermistor in the case of current I passing through it with the thermal conductivity of the gaseous medium, respectively. and, -temperature coefficient. electric thermistor resistance.

Rice. 1. Thermoconductometric. gas analyzer: 1 - source of stabilizers. tension; 2-secondary device; R1 and R3 - working thermistors; R2 and R4 - compare. thermistors; R0 and potentiometers; the inlet and outlet of the analyzed gas mixture are shown by arrows.

In Fig. 1 shows a diagram used in many thermoconductometric tests. gas analyzers. Feels. elements R1 and R3 (working thermistors) are washed with the analyzed mixture; compare thermistors R2 and R4 are placed in sealed cells filled with compar. gas of precisely known composition. Potentiometers R0 are designed to set zero readings and adjust the measurement range. A measure of the concentration of the component being determined is electrical. the current passing through, which is measured by a secondary (i.e. indicating or recording) device. Thermoconductometric gas analyzers are widely used to monitor processes in the production of H2SO4, NH3, HNO3, in metallurgy, etc.

Thermochemical gas analyzers. These devices measure the thermal effect of chemicals. r-tion, in which the determined component is involved. In most cases, oxidation of the component with atmospheric oxygen is used; catalysts - manganese-copper (hopcalite) or finely dispersed Pt deposited on the surface of a porous support. The change in t-ry during oxidation is measured using metallic. or semiconductor thermistor. In some cases, the surface of a platinum thermistor is used as a catalyst. The value is related to the number of moles M of the oxidized component and the thermal effect in the ratio:, where k-coefficient, taking into account heat loss, depending on the design of the device.

The diagram (Fig. 2) includes measuring. a bridge with fixed resistors (R1 and R4) and two thermistors, one of which (R2) is in the atmosphere. gas, and the second (R3) is washed by the flow of the analyzed gas. The voltage Uout in the bridge diagonal is proportional to the concentration of the component being determined. For stable operation of the gas analyzer, the influence of environmental temperatures is eliminated (by thermostatting or temperature compensation), the voltage is stabilized, the gas flow rate is maintained constant, and the gas is purified from impurities that poison the catalyst (C12, HC1, H2S, SO2, etc.).

Rice. 2. Termokhim. gas analyzer: 1 - source of stabilizer. tension; 2-secondary device; R1 and R4 are fixed resistors; R2 and R3, respectively, comparative and working thermistors.

Most thermochemical gas analyzers are used as gas detectors for flammable gases and vapors (H2, hydrocarbons, etc.) in the air at a content of 20% of their lower. CPV, as well as during electrolysis of water to determine impurities of hydrogen in oxygen (measurement range 0.02-2%) and oxygen in hydrogen (0.01-1%).

Magnetic gas analyzers. Used to determine O2. Their action is based on magnetic dependence. susceptibility of the gas mixture on the O2 concentration, volumetric mag. its susceptibility is two orders of magnitude greater than that of most other gases. Such gas analyzers allow selective determination of O2 in complex gas mixtures. The range of measured concentrations is 10-2 - 100%. Naib. Magnetic mechs are common. and thermomagnetic gas analyzers.

In magnetomechanical gas analyzers (Fig. 3), the forces acting in an inhomogeneous magnetic field are measured. field on a body (usually a rotor) placed in the mixture being analyzed. Force F pushing a body out of a magnet. fields is determined by the expression:

where is the volumetric mag. susceptibility resp. the analyzed mixture and a body placed in a gas, V-volume of the body, H-magnetic intensity. fields. Typically, a measure of the concentration of a component is the torque found from the angle of rotation of the rotor. Indications of magnetometer. gas analyzer are determined by magnetic properties of the gas mixture being analyzed and depend on temperature and pressure, since the latter affect the volumetric magnetic field. gas susceptibility.

Gas analyzers made using compensation are more accurate. scheme. In them, the torque of the rotor, functionally related to the concentration of O2 in the mixture being analyzed, is balanced by a known torque, to create which magnetoelectrics are used. or electrostatic systems. Rotary gas analyzers are unreliable in industrial environments and are difficult to adjust.

Rice. 3. Magnetomech. gas analyzer: 1-rotor; 2-pole magnet; 3-stretch; 4-mirror; 5-illuminator; 6-scale secondary instrument.

The operation of thermomagnetic gas analyzers is based on thermomagnetic. convection of a gas mixture containing O2 in non-uniform magnetic and temperature fields. Often used are devices with an annular chamber (Fig. 4), the edges of which are hollow metal. ring. A thin-walled glass tube is installed along its diameter, on which a platinum spiral is wound, heated by electricity. electric shock The spiral consists of two sections - R1 and R2, the first of which is placed between the poles of the magnet. If O2 is present in the gas mixture, part of the flow is directed through the diametrical channel, cooling the first section of the platinum spiral and transferring part of the heat to the second. A change in resistances R1 and R2 causes a change in the output voltage U, proportional to the O2 content in the analyzed mixture.

Rice. 4. Thermomagnetic gas analyzer: 1-ring chamber; 2-glass tube; 3-permanent magnet; 4-source of stabilizers. tension; 5-secondary device; Rt and R2 -resp. the worker will compare. thermistors (sections of a platinum spiral); R3 and R4 are constant resistors.

Pneumatic gas analyzers. Their action is based on the dependence of the density and viscosity of the gas mixture on its composition. Changes in density and viscosity are determined by measuring the fluid mechanics. flow parameters. Common pneumatic three types of gas analyzers.

Gas analyzers with throttle converters measure hydraulic the resistance of the throttle (capillary) when passing the analyzed gas through it. At a constant gas flow rate, the pressure drop across the throttle is a function of density (turbulent throttle), viscosity (laminar throttle) or both parameters simultaneously.

Inkjet gas analyzers measure dynamic pressure of the gas stream flowing from the nozzle. They contain two jet elements of the “nozzle-receiving channel” type (Fig. 5). To submit the analyzed and compare. gases are served by ejector 2. The pressure at the outlet of the elements is maintained by regulator 4. Equality of gas pressures at the inlet to the elements is ensured by the connection. channel 5 and valve 6 settings. Dynamic difference. pressures (pressures) perceived by tubes 1b, is a ratio function and a measure of the concentration of the determined component of the gas mixture. Jet gas analyzers are used, for example, in the nitrogen industry to measure the H2 content in nitrogen (measurement range 0-50%), in the chlorine industry - to determine C12 (0-50 and 50-100%). The time required to establish the readings of these gas analyzers does not exceed several. seconds, therefore they are also used in gas detectors of pre-explosive concentrations of gases and vapors of certain substances (for example, dichloroethane, vinyl chloride) in industrial air. premises.

Rice. 5. Pneumatic jet gas analyzer: 1 - “nozzle-receiving channel” element; 1a-nozzle; 1b-receiving tube; 2-ezhsktor; 3-secondary device; 4 - pressure regulator; 5 - connects, channel; 6-valve.

Pneumoacoustic gas analyzers contain two whistles (Fig. 6) with similar frequencies (3-5 kHz), the analyzed gas passes through one of them, and the comparative gas passes through the second. The frequency of the sound vibrations in the frequency mixer depends on the density of the analyzed gas. Beats (frequency up to 120 Hz) are amplified and converted into pneumatic. amplifier vibrations. To obtain the output signal (pressure), a frequency-to-analog converter is used.

Rice. 6. Pneumoacoustic gas analyzer: 1 - whistle; 2-frequency mixer; 3 - amplifier - converter; 4 — frequency-analog converter; 5-secondary device.

Pneumatic gas analyzers do not have high selectivity. They are suitable for analyzing mixtures in which the concentration of only one of the components changes, while the ratio between the concentrations of the others remains constant. The measurement range is from units to tens of percent. Pneumatic gas analyzers do not contain electricity. elements and therefore can be used in premises of any category of fire and explosion hazard. The circuit elements in contact with gases are made of glass and fluoroplastic, which makes it possible to analyze very aggressive gases (chlorine, sulfur-containing, etc.).

Infrared gas analyzers. Their action is based on election. absorption of IR radiation by molecules of gases and vapors in the range of 1-15 microns. This radiation is absorbed by all gases whose molecules consist of at least two different types. atoms. High specificity of molecular absorption spectra decomposition. gases determines the high selectivity of such gas analyzers and their widespread use in laboratories and industry. The range of measured concentrations is 10-3 -100%. Dispersive gas analyzers use radiation of one wavelength, obtained using monochromators (prisms, diffraction gratings). In non-dispersive gas analyzers, due to the features of the optical. device circuits (use of light filters, special radiation receivers, etc.) use non-monochromatic. radiation. As an example in Fig. 7 shows Naib. a common diagram of such a gas analyzer. Radiation from the source sequentially passes through a light filter and a working cuvette, into which the analyzed mixture is supplied, and enters the special. receiver. If the analyzed mixture contains a component to be determined, then, depending on the concentration, it absorbs part of the radiation, and the recorded signal changes proportionally. The radiation source is usually a heated coil with a wide spectrum of radiation, or less often an IR laser or LED, emitting radiation in a narrow region of the spectrum. If a non-monochromatic source is used. radiation, selectivity of determination is achieved using a selective receiver.

Rice. 7. Non-dispersive infrared gas analyzer: 1-radiation source; 2-light filter; 3-modulator; 4 and 4′-resp. working and compare. (bottom) cuvettes; 5-radiation receiver; 6-amplifier; 7-secondary device.

Naib. Gas analyzers with a gas-filled optical-acoustic receiver are common. The latter is a sealed chamber with a window, filled with exactly the gas whose content needs to be measured. This gas, absorbing a certain part from the radiation flux with a set of spectral lines characteristic of this gas, heats up, as a result of which the pressure in the chamber increases. Through fur. modulator, the radiation flow is interrupted with a certain value. frequency. As a result, the gas pressure in the receiver pulsates at the same frequency. The amplitude of pressure pulsation is a measure of the intensity of radiation absorbed by a gas, depending on what part of the characteristic radiation is absorbed by the same gas in the working cell. Dr. the components of the mixture do not absorb radiation at these wavelengths. Thus, the amplitude of pressure pulsation in the radiation receiver is a measure of the amount of the component being determined in the analyzed mixture passing through the working cell. Pressure changes are usually measured with a condenser microphone or microanemometer (gas flow sensor). Replacing the gas in the optical-acoustic radiation receiver. gas analyzer, you can selectively measure the content of decomposition. components of mixtures.

Infrared gas analyzers also use non-selective radiation receivers - bolometers, thermopiles, semiconductor elements. Then, in the case of sources with a wide radiation spectrum, the selectivity of detection is ensured by the use of interference and gas filters. To increase the accuracy and stability of measurements, part of the radiation flux is usually passed through a comparator. a cuvette filled with a gas that does not absorb the recorded radiation, and measure the difference or ratio of the signals obtained as a result of the passage of radiation through the working one and compare. cuvettes.

Infrared gas analyzers are widely used to control the quality of products, analyze exhaust gases, and indoor air. With their help, they determine, for example, CO, CO2, NH3, CH4 in technol. synthetic gases ammonia, vapors of a number of solvents in the industrial air. premises, nitrogen oxides, SO2, CO and hydrocarbons in vehicle exhaust gases, etc.

Ultraviolet gas analyzers. The principle of their operation is based on select. absorption of radiation by molecules of gases and vapors in the range of 200-450 nm. The selectivity of the determination of monatomic gases is very high. Di- and polyatomic gases have a continuous absorption spectrum in the UV region, which reduces the selectivity of their determination. However, the absence of a UV absorption spectrum for N2, O2, CO2 and water vapor allows, in many practically important cases, to carry out fairly selective measurements in the presence. these components. The range of determined concentrations is usually 10-2-100% (for Hg vapor the lower limit of the range is 2.5-10-6%).

The circuit of the ultraviolet gas analyzer is similar to the circuit shown in Fig. 7. There are also devices with two radiation detectors without a modulator, in which the light streams are not interrupted. The radiation sources usually used are mercury lamps of low (= 253.7 nm) and high (spectrum with a large set of lines) pressures, gas-discharge lamps with vapors of other metals (= 280, 310 and 360 nm), incandescent lamps with tungsten filament, hydrogen and deuterium discharge lamps. Radiation receivers - photocells and photomultipliers. When using a non-selective radiation source, measurement selectivity in most instruments is ensured using optical. filters (glass or interference).

Ultraviolet gas analyzers are used in Sec. arr. for automatic control of the content of C12, O3, SO2, NO2, H2S, C1O2, dichloroethane, in particular in industrial emissions. enterprises, as well as for detecting Hg vapors, less often Ni (CO)4, in industrial air. premises.

Luminescent gas analyzers. In chemiluminescent gas analyzers, the intensity of luminescence excited due to chemicals is measured. r-tion of the controlled component with the reagent in the solid, liquid or gaseous phase. An example is interaction. NO with O3, used for the determination of nitrogen oxides:

N0 + 03 -> N02+ + 02 -> N02 + hv + 02

The diagram of a chemiluminescent gas analyzer with a gaseous reagent is shown in Fig. 8. The mixture to be analyzed and the reagent enter the reaction through chokes. camera. The flow stimulator (pump) provides the necessary pressure in the chamber. If there is a detectable component in the mixture, the radiation accompanying the chemiluminescent solution is fed through a light filter to the cathode of the photomultiplier, which is located directly. proximity to the reaction camera. Electric The signal from the photomultiplier, proportional to the concentration of the controlled component, after amplification, is sent to a secondary device. When measuring weak light fluxes that occur at low concentrations of the component being determined, the photocathode is electrically cooled. microrefrigerators to reduce the dark (background) current.

Rice. 8. Chemiluminescent gas analyzer: 1-rsakts. camera; 2-light filter; 3 - photomultiplier; 4-secondary device; 5-gas flow stimulator; 6-throttles.

To measure the NO2 content, the device is equipped with a converter, where NO2 is converted into NO, after which the analyzed mixture is sent to the reaction. camera. In this case, the output signal is proportional to the total content of NO and NO2. If the mixture enters bypassing the converter, then the concentration of only NO is found from the output signal. The difference in these signals is used to judge the NO 2 content in the mixture.

The high selectivity of chemiluminescent gas analyzers is due to the specificity of the selected solution, however, accompanying components in the mixture can change the sensitivity of the device. Such gas analyzers are used to determine NO, NO2, NH3, O3 in air in the range of 10-7-1%.

Fluorescent gas analyzers measure the fluorescence intensity (wavelength) that occurs when the controlled component is exposed to UV radiation (with frequency v1). As an example in Fig. Figure 9 shows a diagram of such a gas analyzer for determining SO2 in air. The analyzed mixture enters the detector chamber, which is separated from the pulsed source of UV radiation and from the photomultiplier by light filters 3 and 4, transmitting radiation with wavelengths respectively. And. A photomultiplier, located at an angle of 90° to the radiation source, registers fluorescence pulses, the amplitude of which is proportional to the concentration of the component being determined in the chamber. Electric The signal from the photomultiplier, after amplification and processing, is sent to a secondary device. Gas analyzers for determining SO2 are characterized by high sensitivity and selectivity. They are used in automatic environmental monitoring stations.

Rice. 9. Fluorescent gas analyzer: 1 - detector chamber; 2-source of UV radiation; 3-light filter for exciting radiation; 4 - luminescence filter; 5-mirror; 6-photomultiplier; 7-secondary device.

To remove water vapor that affects the readings of fluorescent gas analyzers, special equipment is used. filters (such as molecular sieve) at the inlet of the gas flow into the chamber.

Photocolorimetric gas analyzers. These devices measure the color intensity of selected products. relationships between the component being determined and a specially selected reagent. The process is carried out, as a rule, in solution (liquid gas analyzers) or on a solid carrier in the form of a tape, tablet, powder (respectively, tape, tablet, powder gas analyzers).

Rice. 10. Liquid photocolorimetric. gas analyzer: 1 - radiation source; 2-light filter; 3 and 3′-working and compare. cuvettes; 4-absorber; 5 and 5′ radiation receivers; b-amplifier; 7-secondary device.

A schematic diagram of a liquid gas analyzer is shown in Fig. 10. Radiation from the source passes through the working and compares. cuvettes and goes to the corresponding radiation receivers. The indicator solution flows at a constant speed through both cuvettes and the absorber. The analyzed gas bubbles through the absorber against the flow of the solution. Determined component present in the gas, interaction. with the reagent in the solution, causing a change in optical density in the working cell, proportional to the concentration of the component. As a result, the radiation intensity through one of the cells changes, but not through the other. The difference (or ratio) of the worker signals will be compared. channels - a measure of the concentration of the component being determined in the analyzed mixture.

The supply of the solution can be either continuous or periodic. With periodic Upon delivery, the analyzed gas is passed for a certain time through the same portion of the solution, which makes it possible to increase the sensitivity of the determination. Such gas analyzers make it possible to measure the average concentration of the component being determined over a given period of time, for example. when establishing shift-average or daily average concentrations of toxic impurities in the air.

In tape gas analyzers (Fig. 11), the analyzed gas enters a gas chamber, through which a tape with a reagent applied to it is pulled continuously or at specified intervals. As a result of the reaction with the determined component, a color spot is formed on the tape, the color intensity of which is proportional to the concentration of the component. The difference (or ratio) of light fluxes reflected from the paint. and unpainted tape sections, is a measure of the concentration of the controlled component in the mixture. Sometimes an indicator tape with a liquid reagent is used. In this case, the reagent is applied to the tape from the dropper immediately before it comes into contact with the gas.

Rice. 11. Tape photocolorimetric. gas analyzer: 1 - radiation source; 2-indicator tape; 3-light filter; 4 and 4′ radiation receivers; 5-gas chamber; 6-amplifier; 7-secondary device.

The operating principle of tablet and powder gas analyzers is the same as that of tape analyzers, but these devices are usually cyclical. actions. To obtain a clean surface, the top is cut off before each measurement cycle. painted a layer of tablet or a portion of powder is replaced.

The operating time of tape and tablet gas analyzers without replacing the tape or tablet reaches 30 days or more. Radiation sources in photocolorimetric gas analyzers - usually incandescent lamps and semiconductor LEDs, photodetectors - photomultipliers, photocells, photodiodes and phototransistors. These devices make it possible to determine different types with high selectivity. gaseous (vapor) substances in the concentration range of 10-5-1%. The sensitivity of periodic gas analyzers is especially high. actions; their disadvantage is a slight delay in readings.

Photocolorimetric gas analyzers are used Ch. arr. for measuring the concentrations of toxic impurities (for example, nitrogen oxides, O2, C12, CS2, O3, H2S, NH3, HF, phosgene, a number of organic compounds) in the industrial atmosphere. zones and in industrial air. premises. When monitoring air pollution, portable periodic devices are widely used. actions. Means. number of photocolorimetric gas analyzers are used as gas detectors.

Electrochemical gas analyzers. Their action is based on the relationship between the electrochemical parameter. system and the composition of the analyzed mixture entering this system.

In conductometric gas analyzers, the electrical conductivity of a solution is measured when it selectively absorbs the component being determined. Typically, the device circuit includes electrical. DC or AC bridge with two conductometric cells through which electrolyte flows. The electrolyte enters one of the cells after contact with the flow of the analyzed gas. The output signal is proportional to the difference in the electrical conductivity of the solution before and after contact with the controlled mixture. This difference depends on the concentration of the analyte component dissolved in the electrolyte. By changing the consumption of the electrolyte and the analyzed mixture, it is possible to change the range of determined concentrations within a wide range. The disadvantages of these gas analyzers are low selectivity and the time it takes to establish readings when measuring small concentrations. Conductometric gas analyzers are widely used to determine O2, CO, SO2, H2S, NH3, etc.

The action of potentiometric gas analyzers is based on the dependence of the potential E of the indicator electrode on the activity a of electrochemically active ions formed during the dissolution of the component being determined:

where E° is the standard electrode potential, R is the universal gas constant, T is abs. t-ra, F-Faraday number, n-number of electrons participating in electrochemical. districts. The measured value of E is proportional to the concentration of the controlled component dissolved in the electrolyte. These gas analyzers are used to determine CO2, H2S, HF, NH3, SO2, etc.

Potentiometric ones have become widespread. gas analyzers with solid electrolyte for measuring O2 content. Ceramic a plate based on CaO and ZrO2 at high temperatures begins to conduct oxygen ions, i.e. behaves like an electrolyte. Thin layers of porous platinum (platinum electrodes) are applied to the surface of such a plate on both sides. The analyzed gas mixture is supplied on one side of the plate, and a reference gas on the other. The potential difference between the electrodes is a measure of the O2 content. The thermostat supports the electrochemical temperature. cells in the desired range. Using such gas analyzers, O2 is determined in a wide range of concentrations (10-4-100% by volume). The presence of hydrocarbons in the analyzed mixture leads to distorted results due to their oxidation at high temperatures.

The operation of amperometric gas analyzers is based on the relationship between electrical. current and the amount of the component being determined that reacted on the indicator electrode. If the controlled component completely enters into electrochemical r-tion, then Faraday’s law is satisfied: I = = nFQC, where I-current, Q-gas flow rate, C-concentration of the component being determined, F-Faraday number, n-number of electrons participating in the r-tion.

Electrochem. the transformation of this component of the gas mixture with 100% current efficiency (i.e., the absence of side electrode circuits) is ensured by the choice of an indicator electrode and its potential. The required constant value of the potential difference is maintained due to the fact that it compares. and indicator electrodes are made of two different specially selected metals, for example. from Au and Zn, Au and Pb, Ni and Cd (galvanic type cells). The potential difference can also be stabilized through an electronic system using a third auxiliary. electrode (potentiostatic type cells).

Rice. 12. Amperometric gas analyzer: 1-electrochemical cell; 2-auxiliary electrode; 3-measure, electrode; 4-potentiostat; 5 - reference electrode; 6-amplifier; 7-secondary device; 8-gas flow stimulator; 9-chamber with spare electrolyte.

Amperometric Gas analyzers are used to determine gases that have oxidation-reduction properties. St. you, for example. SO2, NO2, H2S, O2, C12, O3. In gas analyzers for measuring the SO2 content in the air (Fig. 12), the analyzed gas is supplied to the measuring device. electrode 3 electrochemical cells and through the gas channel - into a chamber with a spare electrolyte 9, in which a reference electrode 5 is placed. Auxiliary. electrode 2 is located in a separate chamber, which, like chamber 9, is connected to the measuring chamber. electrode electrolytic channel. Advantages of amperometric gas analyzers - high sensitivity and selectivity.

In addition to the design discussed above, the electrochemical. bubbling-type cells (with direct blowing of the mixture through the electrolyte) cells with the so-called. gas diffusion electrodes, where the gas is separated from the electrolyte by a porous gas-permeable polymer membrane. On the side in contact with the electrolyte, finely dispersed electrode material (Pt, Pd, Au) is applied to the membrane. Such systems are characterized by higher sensitivity and stability of characteristics.

Coulometric gas analyzers are based on compensation. type is the coulometric method. titration, which consists of electrochemical. obtaining (generating) a titrant reagent capable of quickly interacting. with the determined component of the gas mixture dissolved in the electrolyte. This gas analyzer includes generation and indication circuits. Electrochem. cell contains resp. two pairs of electrodevices - a cathode and an anode, on which electrolysis occurs and titrant is generated, and that

Classification by principle of action

Both household and professional models of gas analyzers can be either manual or automatic. Among the first, absorption chemical ones have become more widespread - in them, the components of the gas-air mixture are absorbed one by one using special reagents. Automatic - capable of measuring physico-chemical or physical indicators of a gas substance (its individual components) simultaneously.

Manual models have not been used by mass users for a long time; the market is almost completely conquered by automatic devices, which can be divided into three groups according to their operating mechanism:

The action is based on methods of physical analysis and includes additional chemical reactions. These models are capable of determining changes in pressure or volume of a gas substance based on chemical reactions with its individual components.
The action is based on methods of physical analysis and includes additional thermochemical, photocolorimetric, and electrochemical processes. Thermochemical ones are based on measurements of the efficiency of the thermal combustion reaction (catalytic oxidation). Electrochemical can determine the concentration of substances in a substance based on the conductivity values produced by the electrical electrolyte that has absorbed the substance. Photocolorimetric methods are based on a change in the color spectrum of certain substances during their interaction with the analyzed elements.
The action is based on exclusively physical determination methods (optical, thermoconductometric, thermomagnetic). Thermoconductometry measures the thermal conductivity of a gas substance. Thermomagnetic are capable of determining oxygen concentration, where oxygen will have increased susceptibility to magnetic fields. Optical ones are based on measurements of optical density, emission/absorption spectra of the gas-air mixture.

Each of the methods described above has its own advantages and disadvantages, however, modern manufacturers of gas analysis devices most often use the electrochemical principle of operation in their designs, as the simplest, cheapest and most multifunctional. But this method also has its disadvantages, namely:

Low selectivity and accuracy of the results obtained;
Short service life of sensitive elements;
Greater susceptibility to negative effects from the analyzed impurities.

The best thermoconductometric portable

The most common type of devices. The principle of operation is based on identifying the dependence of the electrical resistance of special conductors on the concentration of gases. The quantitative and qualitative composition of gas mixtures affects their thermal conductivity. The gas mixture enters a cylindrical cell, changing the temperature of the heating device. The corresponding signal is sent to the device display.

GX-2003

Country of origin: Japan. One of the most advanced models of multigas analyzers. Currently, the portable device has been discontinued from mass production, but it can still be found on sale.

M-02

Country of origin: Russia.
The model is included in the state register and has general industrial purposes. Used for operational measurements of the concentration of toxic and explosive gases. Threshold values are indicated by light and sound signals up to 75 dB. Simultaneously, M-02 can analyze up to 4 components of a gas mixture. Battery life up to 70 hours. Operating temperature range from -40°C +60°C.

Advantages:

the ability to adjust sensitivity modes;
availability of a memory function for measurements for the last 48 hours;
self-diagnosis;
light weight and overall dimensions;
battery charging indicator.

Flaws:

not identified.

Review

Mikhail H.

I take the device with me into the mine. Works for three years without breakdowns.

Problems of wise choice

Before purchasing a gas analysis device, it is necessary to take into account the level of security of its housing and switching capabilities in general. Independent and stationary sensors do not necessarily have to communicate with controllers or computers. In cases where you need a household appliance equipped with a gas supply shutoff module, then the presence of ports such as RS-232 (for switching with a computer) and a control relay will be needed. A relay will especially be needed to ensure that the device is properly integrated into complex security devices (for example, into a smart home system). Then the device will be securely connected to the gas system valve regulators, siren and hood.

The level of protection of the housing is indicated according to the European IP standard. Household models for residential premises usually have a protection class of IP20, which indicates high-quality resistance to moisture and dust. The most wear-resistant models have a protection class of IP67 - they successfully withstand aggressive chemical environments, can be completely immersed in water, etc.

The following parameters will also be useful guidelines:

Number of types of identified harmful substances;
The method of air selection can be automatic, using a compressor, or manual (i.e. forced).
Stationary or portable placement - everything here will depend only on the conditions of future use.

At the same time, you should pay attention to the maximum total load of the device - i.e. This refers to the time between failures (quality and durability of sensors, pumps, alarms, etc.). Separately, it is necessary to inquire about the steam circulation system and its maximum load.

If you choose a device for determining the flue (exhaust) gases of fuel-burning boilers, then the easiest way is to be guided by the principle - “the more expensive, the better,” because this category is the most common and manufacturers try to make it as functional as possible. In all other cases, for example, when choosing for industrial purposes, you need to start from the number of functions: a large device for monitoring gases in a smelting shop is unlikely to be needed with all its large set of functions in a woodworking shop. Accordingly, there is no point in overpaying for extensive functionality.

Separately, one should take into account an important economic factor, namely the price of annual maintenance. It is calculated as the total cost of periodic technical inspections, replacement of consumables, and ongoing sensor calibration.

In any case, before purchasing, the buyer must request certification documentation from the seller:

Certificate or certificate for the type of measuring instrument;
Instructions describing the means of accounting and control;
Verification method;
Methods for performing measurements.

IMPORTANT! Measuring gas emissions is a matter of state control/supervision and without the appropriate certification measurements, the device cannot be used!

Application of gas analyzers[edit | edit code]

Ecology and environmental protection: determination of the concentration of harmful substances in the air.
In control systems for internal combustion engines, for example, lambda probe) and regulation of the combustion process in boilers of thermal power plants.
In chemically hazardous industries.
When determining leaks in refrigeration equipment (so-called freon leak detectors).
When determining leaks in gas and vacuum equipment ( helium leak detectors ).
In explosive and fire hazardous industries to determine the content of flammable gases as a percentage of the LEL.
In diving to determine the composition of the gas mixture in diving cylinders;
In basements, wells, pits before work.
In medicine, “multigas” provides control of the concentration of gases in the breathing circuit during anesthesia.
In transport, when ensuring transportation safety (search for explosives, drugs).

Many modern gas analyzers often have additional functions, for example:

Gas differential pressure measurement to measure gas flow.
Determination of speed and volumetric flow of gas flow.
Determination of gas/gasoline consumption.
Built-in memory.
Interface, also a wireless interface, for transferring data to a computer.
Statistical processing of measurement results.
Calculation of mass emissions of harmful substances.

Rating of the best gas analyzer models for 2021

Budget options

3rd place: "BG 2202 Brennenstuhl 1290460"

Stationary ceiling-type model. At first glance, it may seem that it is intended only for domestic use, but it can also cope with increased concentrations of analyzed substances, so it can be installed even in a boiler room. Operates from a 220 V network. The alarm system is both audio and visual. Positioned by the manufacturer as a model for rooms with a large presence of people. Price – 2000 rubles.

gas analyzer BG 2202 Brennenstuhl 1290460

Advantages:

Excellent audible/visual alarm;
Budget price;
Ease of installation.

Flaws:

Low threshold for detectable dangerous concentration – from 40%;
Does not work when power is off.

2nd place: “Mastech MS6310 65299”

Despite the fact that the device is made by a Chinese manufacturer, its design contains high-quality parts. In addition to the main functions, it has the function of detecting gas leaks in the pipeline. Made in the form of a small portable model. Operates on four AA batteries (9 hours of uninterrupted operation). Characterized by high response speed. The sample is taken using a flexible probe. Price – 4500 rubles.

Mastech MS6310 65299

Advantages:

Durable housing;
Long comfortable probe;
Easy to manage.

Flaws:

There is no display.

1st place: “MEGEON 08005”

A good example from a domestic manufacturer. It is easy to operate, fits perfectly in the hand, has a large display and is lightweight. Automatically measures ambient CO2 and even air temperature! Characterized by relatively high measurement accuracy and increased sensitivity. Operates on two AA batteries. Positioned as a device for frequent use. Price – 9100 rubles.

MEGEON 08005

Advantages:

Light weight;
Power supply charge indicator;
Multifunctional.

Flaws:

Long response time – about 60 seconds.

Middle price segment

2nd place: “SEM DT-802 481769”

A stationary version designed exclusively for the determination of carbon monoxide. It can be placed either on a stand or mounted on a wall. In the dark, you can use the screen backlight. Due to its small size, with the help of an extension, it can be used as a leak trap. The display contains indicators of temperature, gas pollution, calendar and clock. Extremely fast response time - only 2 seconds. Price – 9700 rubles.

SEM DT-802 481769

Advantages:

Informative display;
Versatility;
Small dimensions;
Backlight.

Flaws:

Power supply only from 220 V mains.

1st place: “Testo 317-2”

An excellent example, capable of working even in sub-zero temperatures. The model is portable, characterized by ease of operation and an informative display with night backlight function. The product comes in a branded case, so the safety of storage/transportation does not raise any questions. Has increased accuracy. Price – 14,000 rubles.

Testo 317-2

Advantages:

Operates at sub-zero temperatures;
There is a case for storage and carrying;
Convenient to use.

Flaws:

2 batteries are enough for only 4 hours of operation.

Premium segment

2nd place: “MEGEON 08002 k0000017420”

A rather heavy option (almost 300 grams), however, it has increased accuracy. Battery operated. It has a flexible probe, which makes it very easy to take measurements. If the specified standards are exceeded, it signals with both sound and light. The average response time is about 10 seconds. The kit comes with not just a cover, but a very convenient case with soft inserts. Despite the Russian assembly, sensitive sensors in the design are used from a European manufacturer. Among buyers it has earned the characteristic “Best price/quality ratio”. Cost – 14,000 rubles.

MEGEON 08002 k0000017420

Advantages:

Double notification - sound and light;
Battery and mains operation;
Extended service life.

Flaws:

Not detected (for its segment).

1st place: “Testo 316-1”

An extremely high-precision device, which increases its price by orders of magnitude, even despite the lack of a display. The battery life is enough for 5 hours of continuous operation. Response time is about 5-30 seconds. Capable of identifying up to 5 harmful components. The indication is made in the form of two signal lights: yellow – “attention”, red – “potential danger”. Equipped with a flexible probe. Price – 20,000 rubles.

Testo 316-1

Advantages:

Durable housing;
Convenient probe;
Very high accuracy.

Flaws:

Overcharge.

Installation of gas analyzers

In families of household analyzers there are also stationary models that require special installation. At the same time, they are also distinguished by their compact size, ease of maintenance and low performance characteristics. Installation of such a device is usually carried out in a place where there is an increased risk of gas leakage. This may be an area next to a boiler installation, boiler or stove. Mounting is most often carried out on the wall in such a way that the user has direct access to the control panel of the device. The gas analyzer is fixed using a mounting profile, which usually comes in the basic kit. Using screws or self-tapping screws, it is necessary to install the supporting panel, and then integrate the device itself into it. Depending on the type of model, it may also be necessary to lay a power cable from the mains, although household low-power analyzers often operate on rechargeable batteries.

Instructions for use and storage

Installation, use and verification of work area air gas analyzers must be carried out in strict accordance with the conditions specified by the manufacturer.

Storage requirements vary depending on the analyzer device . For example, electrochemical devices are stored in supplier packaging in a heated storage facility at temperatures from +5ºС to +40ºС and can withstand high humidity.

Optical devices allow a temperature range from -50ºС to +50ºС , but are sensitive to sudden changes in temperature and humidity, as well as dust, aggressive vapors and other harmful impurities.

An adequately selected, serviceable and correctly used gas analyzer provides accurate and timely information about the composition of the air in the work area . This information may be not only necessary, but also vital for the employee.

In conclusion, we suggest watching a video review of how the FP11.2K gas analyzer works:

A gas analyzer is a device designed to measure the concentration of individual components in gas and air mixtures.

Depending on the model, the device can provide the user with numerical measurement values or signal when the maximum/minimum set level is exceeded. Analyzers operate in both manual and automatic modes.

Selection rules

In order to choose the right device for monitoring the air of a working area, you must, first of all, proceed from the list of impurities that need to be determined. In addition, the hazard class of impurities matters : there are modifications of devices for explosive and non-explosive environments.

Sample models of industrial gas analyzers are shown in the photo:

Depending on the tasks assigned - general, local or individual , stationary, portable or portable models of gas analyzers are chosen. And finally, devices with different operating principles have their own advantages and disadvantages .

Thus, thermochemical devices have a low cost, but at the same time a short service life of the gas analyzer sensor, low speed and sensitivity, and a small range of measured concentrations. Thermochemical analyzers are used primarily to monitor the air in a production area for the content of flammable gases, for example, CO.

Electrochemical analyzers occupy an average price position. They have high sensitivity, a wide range of detectable substances, and low energy consumption. At the same time, they are large in size and difficult to maintain.

Optical devices have excellent performance, high selectivity and sensitivity. Their measurement range covers almost the entire range of possible contaminants. At the same time, the cost of optical gas analyzers is the highest.

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Features of household gas analyzers

Models for home use are small in size, modest in performance and simplified controls. If professional devices require stationary operation, then a household device provides the ability to move. Its functionality is designed to search for leaks and examine gas vapors at different points. At the same time, in the segment of home devices there are different levels of functional content. For example, a household gas analyzer from the budget category works with a simple warning system, which can be represented by a light or sound indication. That is, if in the apartment there is an excess of the concentration of gas vapors relative to the standard value, the detector will give a corresponding signal, but without additional information. More complex household models are equipped with a display that displays data with detailed characteristics of the environment under study.

Operating principle

In the catalogs, gas analyzers are presented in several types of models.

They differ in their operating principle:

thermal conductometric - work on the basis of the dependence of the thermal conductivity of a gas or air mixture on its composition. Selective, highly sensitive devices;

thermochemical - a catalyst is installed in the device body, on which the component being determined is oxidized or another reaction occurs with its participation. The concentration is determined by the thermal effect of the process;

magnetic - designed to determine the oxygen content. The operating principle of the devices is based on the dependence of the magnetic susceptibility of the mixture on the O2 concentration;

pneumatic - determine the density and viscosity of the gas mixture, which depends on the qualitative and quantitative composition;

infrared - analyze the degree of absorption of IR rays by different components of the gas mixture. The equipment is highly selective in relation to compounds whose molecules consist of two or more atoms, therefore it is widely used in laboratory conditions;

ultraviolet - generate radiation in the range of 200-450 nm. The devices are effective for determining the concentration of monatomic gases;

luminescent - work on the basis of the phenomenon of luminescence, which occurs as a result of a chemical reaction of the component being determined with the reagent;

photocolorimetric - measure the color intensity of substances obtained as a result of the reaction between a specific reagent and the component being determined. The peculiarity of gas analyzers of this type lies in the different aggregate states of the reagent. The process can take place in the liquid phase or on a solid carrier: tablet, tape, etc.;

electrochemical – measure the electrochemical characteristics of the analyzed mixture. The devices have low selectivity;

ionization - determine the electrical conductivity of the medium, which depends on the type, quantity, and mobility of ions of different components.

Purpose, main elements, types, principle of operation

Gas analyzers are devices with the help of which the composition of a gas mixture is determined, both qualitative (which gases are present) and quantitative (how many specific gases are in the mixture).

First of all, fire, explosion and chemically hazardous industries are equipped with gas analyzers, as well as mines where there are accumulations of firedamp (methane) .

Application for personal protection

Small portable gas analyzers are supplied to workers in hazardous industries , can be considered primary personal protective equipment.

They promptly signal an increased content of harmful impurities in the air, at which point you should leave the work area or use respiratory protection. The gas analyzer device is shown in the photo:

Device operation method

Manual analyzers , which are operated by an operator, are based on the fact that individual gaseous components are absorbed by special reagents.

The air from the production area is passed through an absorber , which binds a specific gas. After this, the initial volume of the mixture decreases. By reducing the volume, it is calculated how much gas bound by the absorber was initially contained there. Depending on the skill of the operator, the measurement takes from five to ten minutes .

The physical principle of measuring the result of an auxiliary chemical reaction ensures the operation of volumetric manometric or chemical analyzers. These instruments measure how much the volume or pressure of a gas mixture has changed after its components have entered into certain chemical reactions.

The following devices have a physico-chemical principle of operation, combined with a physical one:

Chromatographic . In them, the sample is separated due to the fact that different gases pass through the absorption layer, each at its own individual speed. The result of the separation is recorded and an automatic calculation is carried out.

Thermochemical . In these devices, oxidation (with additional catalysts) of the components of the gas-air mixture takes place. Oxidation produces heat; temperature is measured by a thermistor. The concentration of the components is determined by the degree of heating.

Photocolorimetric . In them, the content of components is measured by the result of their color reaction with indicator substances.

Electrochemical gas analyzers determine the concentration of gas in a mixture by the electrical conductivity of the solution that absorbs this gas.

The following automatic gas analyzers have purely physical principles of operation:

Thermoconductometric . When the composition of the gas mixture changes, its thermal conductivity changes. This change is recorded by thermistors.
Densimetric . The density of the gas mixture is measured, which varies depending on the quality and quantity of gases included in it.
Magnetic . They are used to measure the oxygen concentration in the air of a production environment based on its magnetic properties.
Optical . The composition of the gas mixture is analyzed by its optical density, as well as emission or absorption spectra.

Varieties

In addition to differences in the method of operation (manual or automatic) and principle of operation, gas analyzers for air in the working area are divided into types:

Stationary . Such devices automatically monitor gas concentrations. In an industrial version, if the permissible content of a dangerous gas component is exceeded, they give light and sound signals, and also turn on ventilation and other safety systems;
Portable . Designed to determine the concentration of gas impurities in different places of the production area;
Portable . Individual devices. They are small in size and weight, and measure the concentration of harmful impurities directly where the worker is located.

In addition, according to the number of measured impurities, these devices are single- and multi-component , and according to the number of channels (sensors or sampling points) - single- and multi-channel.

Popular portable optical

The operating principle of the devices is based on measuring the radiation of energy flows. The devices have two cameras. One of them is filled with clean air, and the other with the analyzed gas mixture. The concentration of substances is determined by the difference in the obtained measurement results. The models have high resolution. This allows them to be used for analyzing microconcentrations of hazardous substances in industrial gases.

PGA-200

Country of origin: Russia. The model is included in the state register and has an explosion-proof design. Designed to measure the concentration of explosive and toxic gases. PGA-200 is used as a personal device. Light weight (0.3 kg) allows you to carry it in your work clothes pocket.

When determining the maximum permissible concentration of substances, the gas analyzer gives light and sound signals. Operating temperature range from -20°C to +40°C.

Advantages:

accelerated battery charging;
ability to connect to a PC;
autosaving of measurement results.

Flaw:

the need to warm up the device before starting measurements.

Review

Artyom D.

Compact device with good measurement accuracy. Works without breakdowns.

ANCAT-7664Micro

Country of origin: Russia. The model is included in the State Register. The device can measure up to 4 components in various combinations. The concentration of each substance in the gas mixture is displayed on a digital display. A sound and light indicator signals an increase or decrease in the maximum permissible concentrations of substances.

Advantages:

possibility of manual adjustment of alarm limits;
there is a function of forced sampling;
saving inspection results for a year;
ability to work without calibration for up to 6 months;
availability of explosion protection;
light weight and size.

Flaws:

not identified.

Review

Gennady Yu.

I bought the device more than 2 years ago. I use it every day. There are no complaints about the work.

Features of such devices

The advantages of portable gas analyzers are their compactness and light weight.
The devices are among the personal protective equipment provided to workers in hazardous industries. If the concentration of certain substances in the air exceeds the concentration, the devices give a corresponding signal. Portable gas analyzers can be used in any room and conditions.

Gas analyzers are used to determine:

level of gas contamination and vapors of petroleum products;

gas leaks.

The devices have a low cost, which allows you to purchase them for personal purposes. Modern portable gas analyzers are capable of measuring the concentration of several substances in mixtures at once. Manufacturers produce devices of various types, based on different operating principles.