A simple automotive single-component gas analyzer is designed to measure the content of only carbon monoxide CO in exhaust gases, mainly using the method of afterburning incompletely burned components in the exhaust gases. Afterburning of CO is carried out in the measuring chamber of the device using a special heated filament, and the change in the temperature of the filament characterizes the CO content in the gases. The accuracy of the readings of such a gas analyzer is low and depends largely on the content of another component - CH hydrocarbon.
Figure 3. Schematic diagram of a two-component gas analyzer for CO and hydrocarbons
1 - probe; 2...4 - filters; 5 - pump for supplying exhaust gases; 6 - measuring cell (chamber); 7 - source of infrared radiation; 8 - synchronous motor; 9 - shutter; 10 - comparative cuvette (chamber) CO; 11 - infrared radiation receiver CO; 12 - membrane capacitor; 13, 16 - amplifiers; 14 - comparative cuvette (chamber) C n H m; 15 - infrared beam receiver С n Н m; 17, 19 - indicators of hydrocarbon and CO content; 18 - measuring cell (chamber) C n H m
Content Definition harmful substances in exhaust gases using modern multi-component gas analyzers for cars is carried out without the use of chemical reagents, mainly by thermal (infrared) measurement method. The method is based on the principle of measuring the absorption of thermal radiation by various components of exhaust gases. The spectrometric unit of a modern gas analyzer operates on the principle of partial absorption of the energy of the light flux that passes through the gas. The molecules of any gas are a vibrational system that is capable of absorbing infrared radiation only in a strictly defined wavelength range. Thus, if a stable infrared flow is passed through a flask with gas, then part of it will be absorbed by the gas. Moreover, in this case, only that small part of the entire spectrum of the light flux, which is called the absorption maximum of a given gas, will be absorbed. Moreover, the higher the gas concentration in the flask, the greater the absorption will be observed.
Measuring the concentration of a particular gas in a gas mixture by measuring the absorption of the corresponding wavelength allows the fact that different gases correspond to different absorption maxima. Thus, the concentration of each gas in the engine exhaust can be determined by measuring the decrease in the intensity of the light flux in that part of the spectrum that corresponds to the absorption maximum of a certain gas.
The spectrometric unit of the device operates as follows:
Exhaust gases, previously filtered and cleared of soot and moisture, are pumped through a measuring cuvette, which is a tube with ends covered with optical glass. An emitter is installed on one side of the tube, which is a spiral heated by electric current, the temperature of which is strictly stabilized at one level. Such an emitter generates a stable stream of infrared radiation.
On the other side of the measuring cuvette, light filters are installed, which from the entire radiation flux select those wavelengths that correspond to the absorption maxima of the gases being studied. The flow, after passing through the light filters, enters the IR radiation receiver, which measures the intensity of this flow and converts it into information about the concentration of gases in the vehicle exhaust.
Since this method is applicable only for measuring the concentrations of CO 2, CO and CH, at the next stage the mixture of exhaust gases from the measuring cell is supplied sequentially to electrochemical type sensors for measuring oxygen O 2 and nitrogen oxides NO X. At the same time, electrochemical sensors produce an electrical signal with a voltage proportional to the concentration of oxygen and nitrogen oxides.
Thus, the concentration of all significant gases is measured: CO, CH and CO 2 - using the psychrometric method, O 2 and NO X - using electrochemical sensors. Processing of signals from the spectrometric unit and electrochemical sensors in a modern gas analyzer is carried out using a microprocessor electronic circuit.
After processing the signals, information about the gas content is displayed on the device screen: CO, CO 2 and O 2 - in percent, and CH and NO X - in ppm (parts per million), “parts per million”. The designation in ppm is due to the fact that the concentration of such gases in the exhaust is extremely small, and therefore it is inconvenient to use percentages to indicate their quantity.
The relationship between percentage and ppm can be described by the following equation:
For example, in the exhaust gases of a conventional engine internal combustion passenger car CH content is about 0.001%-0.01%. The difficulty of using such values in work predetermined the widespread use of ppm as a unit of concentration.
A gas analyzer is a complex device, the quality of which, first of all, is determined by the accuracy and reliability of the spectrometric unit. The spectrometric unit is the most complex and expensive part of the device, therefore, during operation, it is very important to create conditions for its safety and durability. Soot, moisture and other mechanical particles, settling on the walls of the block, lead to a noticeable scatter in the readings of the spectrometric block, and ultimately to its breakdown. Therefore, before entering the measuring unit, exhaust gases must undergo special preparation, which usually consists of several stages:
rough cleaning of exhaust gases. This is done using a filter that is installed at the inlet of the device, or directly in the sample collection probe. At this stage, the exhaust gases are cleaned of soot and other large mechanical particles.
purification of exhaust gases from moisture. It is produced using a moisture separator, which can have a wide variety of designs. At this stage, droplets of moisture are separated from the gas flow and then removed, which condense on the internal surfaces of the probe, as well as the connecting hose. Condensate is removed from the storage tank either automatically or manually by the operator.
fine filtration. Using a fine filter, the final filtration of the smallest mechanical particles is carried out. Filters fine cleaning There may be several, and they are installed sequentially one after another.
A gas analyzer is an electro-optical device for measuring the volume fraction of components in engine exhaust gases.
Gas analyzers come in 1,2,3,4,5-component types. Measured exhaust gas components: CO, CH, CO2, O2, NOx. We know that all modern gasoline cars (except cars with direct injection fuel into the cylinders and layer-by-layer distribution of the mixture) in steady-state modes (except for full load mode) should operate at a stoichiometric air/fuel ratio (Lambda equal to 1). Moreover, the accuracy of maintaining this ratio is quite high (Lambda = 0.97-1.03). Lambda is an integral parameter that allows you to evaluate the quality of the working mixture. And the quality of combustion of the mixture can be assessed by the composition of the exhaust gases. For diagnostic tasks, it would be correct to use 4 and 5-component gas analyzers, and those that are capable of calculating the Lambda coefficient.
For autodiagnostics, a 4-component gas analyzer is indispensable. It helps to look inside the combustion chambers of a running engine and determine how the combustion process of the fuel-air mixture proceeds. This mixture should, if possible, burn completely in the engine so that the maximum fuel consumption can be achieved with low fuel consumption. possible power engine and keep the resulting harmful substances as low as possible from the very beginning. Absolutely perfect combustion is impossible even with ideal air fuel mixture, since the time available for this is too short, even with the best design and optimal adjustment of all components important for combustion. From a theoretical point of view, combustion would be perfect with a fuel to air weight ratio of 1:14.7 or, representing in volume, 1 liter of fuel mixed with 10,000 liters of air. This ratio is denoted lambda.
The analyzed gas enters the analyzed cuvette, where the components being determined, interacting with the radiation, cause its absorption in the corresponding spectral ranges. Radiation fluxes of characteristic regions of the spectrum are separated by interference filters and converted into electrical signals proportional to the concentration of the analyzed components. When interacting with oxygen, the electrochemical sensor produces a signal proportional to the oxygen concentration. The l value is calculated automatically by the gas analyzer based on the measured CO, CH, CO2 and O2.
Modern gas analyzers high class, in addition to reliability and ease of use, they have many additional functions. They can measure rotational speed crankshaft engine, oil temperature, as well as remember intermediate measurement protocols and transfer the results to a personal computer or print them on the built-in printer.
A very important quality of a gas analyzer from the operator’s point of view is its reliability. Since, by its design, a gas analyzer is a complex electronic device, it is usually impossible to repair it on your own and you have to contact a branded service center, which is extremely inconvenient, therefore, when choosing a gas analyzer model, you should pay attention to its protection from external influences and the presence of a gas pre-treatment unit.
From the article you will learn how to make a lambda probe decoy with your own hands and whether it is worth installing it on your car. Its coefficient depends on how well the air-fuel mixture burns in the engine. useful action. It is very important to choose the optimal proportion of gasoline and air content depending on the load on the engine.
If in old cars all settings for the quality and quantity of fuel depended on the carburetor adjustments, then in modern cars the situation is somewhat different. Everything is in the safe hands of microprocessor technology and a huge number of sensors.
How does an injection system work?
We can highlight several of the most important components that are present in the injection system:
- Fuel tank.
- fuel in one housing with pump and filter.
- Fuel rail (installed in engine compartment on the intake manifold).
- Injectors that supply the gasoline mixture to the combustion chambers.
- Control block. As a rule, it is mounted in the car interior and allows you to control the supply of the air-fuel mixture.
- An exhaust system that ensures the complete destruction of harmful substances.
It is in the latter that the lambda probe blende is installed. You can make it quite simply with your own hands (it doesn’t matter whether you have a Lancer 9 or a Lada). But you should also be aware of all the consequences of installing a “stub”. A do-it-yourself lambda probe decoy for a Priora can be made of a simple design, in any case it will have a significant impact on the operation of the engine.
How many sensors are there in a car?
Mounted in the exhaust system modern cars With injection system fuel injection. The system can have either one or two oxygen sensors. If one is installed, it is located after the catalytic converter. If there are two, then before and after.
Moreover, one measures the percentage of oxygen immediately at the exit of the cylinders and sends its signal to the electronic control unit. The second one, which is mounted after the catalyst, is necessary to correct the readings of the first one.
The principle of operation of the lambda probe
All car electronics, which is responsible for the correct formation of the mixture, is involved in the distribution of fuel among the injectors. Using an oxygen sensor, the required amount of air is determined to form a high-quality mixture. Thanks to fine adjustments of the lambda probe, a high degree of environmental friendliness and efficiency can be achieved.
The fuel burns completely, and the air coming out of the pipe is almost clean - this is an environmental plus. The most precise dosage of air and gasoline is a gain in fuel economy. Of course, together with oxygen sensors it ensures stable engine operation. But due to the fact that it is made of precious metals, its cost is extremely high. And if it fails, replacing it will cost a pretty penny. Therefore, the thought arises: “But there is a lambda probe trick; it won’t be difficult to do it yourself (the VAZ-2107 even needs to replace the oxygen sensor).
Design features of the oxygen sensor
The appearance of this device is simple - a long electrode body from which wires extend. The body is coated with platinum (it is this precious metal that was discussed above). And here internal organization more "rich":
- A metal contact that connects wires to connect to the active electrical element of the sensor.
- Dielectric seal for safety. It has a small hole through which air enters the housing.
- Concealed zirconium electrode, which is located inside the ceramic tip. When current flows through this electrode, it is heated to a temperature in the range of 300...1000 degrees.
- Protection screen with a hole for exhaust gases.
Sensor types
There are two main types of oxygen sensors that are currently used in automotive technology:
- Broadband.
- Two-point.
Regardless of the type, they have an almost identical internal structure. There are also external similarities, as you understand. But the operating principle is significantly different. The wideband oxygen sensor is an upgraded two-point sensor.
It contains a pumping component, which, thanks to voltage fluctuations, sends a signal to the electronic control unit. The current supply to this element can either increase or become weaker. In this case, a small amount of air enters the gap and is analyzed. It is at this stage that the CO concentration in the exhaust gas is measured. But sometimes you make and install a lambda probe decoy yourself. "Chevrolet Lanos", for example, works stably with it and does not display errors after refueling with bad gasoline.
Determining whether the oxygen sensor is faulty
Of course, this element is not eternal, despite its high cost and platinum in the composition. Of course, the lambda probe is no exception and at one point may die for a long time. And some symptoms will appear:
- The level of CO content in exhaust gases increases sharply. If an oxygen sensor is installed on the car, and the CO level is extremely high, this indicates that the control device has failed. The content of harmful substances can only be determined using gas analyzers. But it is unprofitable to purchase it for personal purposes.
- Notice sharply on-board computer. Look at your current gas mileage. This is the easiest way. You can also judge by the frequency of refills.
- And the last sign is the light on dashboard a lamp indicating the presence of malfunctions in the engine.
If it is not possible to analyze the exhaust gas using a special device, this can be done visually. Light smoke is a sign that there is too much air in the fuel mixture. Black indicates a large amount of gasoline. Therefore, it can be judged that the system is not working properly. But the picture is different if there is a lambda probe. Making such a device with your own hands (Volkswagen, VAZ, Toyota - for any car) is quite simple.
Causes of breakdowns
It is worth paying attention to the fact that the oxygen sensor is located at the epicenter of fuel combustion. Consequently, the composition of gasoline has a significant impact on the operation of the lambda probe. If gasoline contains many impurities, does not comply with GOST, or is of poor quality, then the oxygen sensor will generate an error or an incorrect signal to the electronic control unit. In the worst case, the device fails. And this happens due to the high content of lead, which is deposited on the sensor and impairs its functioning. But there may be other reasons for breakdowns:
- Mechanical impact- vibrations, too active use of the car, lead to damage or burnout of the body. It is impossible to repair or restore; the rational solution is to buy a new one and install it.
- Incorrect operation of the fuel supply system. If the air-fuel mixture does not burn completely, soot begins to settle on the lambda probe housing and also gets inside through the air intake holes. Of course, cleaning the device helps at first. But if it needs this procedure more and more often, then you will have to install a new device.
Try to diagnose your car from time to time. In this case, you will not be surprised if any element fails.
Troubleshooting
Of course, the most accurate answer about breakdowns will only be given by diagnostics using specialized equipment. But you can identify a sensor failure yourself; just read carefully about the features of the sensor and its characteristics. But it is extremely rare for a lambda probe to be installed. You can literally make a fake plug with your own hands (VAZ-2114 or any other car if you have one) using improvised means, literally. The troubleshooting algorithm is as follows:
- Open the hood and find the exhaust manifold. Work must be carried out on a cooled engine, as serious injuries can occur. Locate the lambda probe on the catalytic converter.
- Carry out an external inspection. Pollution, soot, light deposits are signs of improper operation of the fuel system. Moreover, the last sign indicates that there is too much lead in the gases.
- Replace the oxygen sensor and diagnose all fuel system again. If no contamination is observed, you need to continue troubleshooting.
- Disconnect the sensor plug and connect to it a voltmeter with a scale of up to 2 Volts. Start the engine and increase the speed to 2500 rpm, then reduce it down to idle move. The voltage change should be insignificant - in the range of 0.8..0.9 volts. If there is no change, or the voltage is zero, we can talk about a breakdown of the sensor.
You can also judge the breakdown by other characteristics. You create an artificial vacuum in the vacuum tube. In this case, the voltage should be very low - less than 0.2 Volts.
Oxygen sensor life
To ensure smooth and stable operation of the car, you need to regularly carry out technical inspections. For example, a lambda probe needs to be inspected every 30 thousand kilometers. Moreover, its service life is no more than one hundred thousand - you should not operate a car with an old sensor - this will only lead to the fact that the engine will have to be repaired much earlier. And the question arises - will the lambda probe blende fit your car? You can make such a device on Kalina with your own hands in a few minutes.
But there is one nuance. The motorist cannot guarantee that the fuel he fills the car with is of high quality. Of course, everyone is used to filling up with the gasoline that is sold at their favorite gas station. But who knows what the composition of the gasoline that is bottled there is? Therefore, try to trust “brand” gas stations that value their name. But if there are no good gas stations nearby, you will have to be content with what is available nearby. And a burning engine error lamp is a common occurrence, and installing a blende will help get rid of it.
Homemade decoy device
It all depends on what funds you have at your disposal. It is worth noting that making a lambda probe with your own hands on a VAZ can be the most democratic, it still works flawlessly. The cheapest option is homemade. The body is made of bronze. It is better to choose this metal, as it has a very high resistance to heat. Moreover, the dimensions of this blank must be exactly the same as that of the sensor itself, so that exhaust vapors do not leak out. Essentially, this is a spacer with a small hole - no more than three mm. This spacer is screwed into place of the sensor. And the lambda probe itself is installed in the spacer.
Between the sensor and the hole in the blank there is a layer of ceramic chips on which a layer of catalyst is applied. Thanks to this, it passes through a thin hole and is oxidized by crumbs. The result is a significant reduction in CO levels. Consequently, the standard oxygen sensor is deceived. But such devices can be installed on budget cars. More expensive cars should not be altered.
Electronic snag
But if you have installation skills electrical diagrams, can be made homemade device. You only need one of these two elements - a resistor or a capacitor. But such a lambda probe decoy is not suitable for everyone. You can make it with your own hands (Subaru Forester or VAZ, it doesn’t matter) according to one of the proposed options. But be careful, because a lack of understanding of the deception process will affect the functioning of the entire control unit. And if you are not sure, it is better to purchase a ready-made one on a microcontroller. It is good because it can independently carry out the following actions:
- Assess the gas concentration at the first sensor.
- Next, a pulse is formed that corresponds to the signal that was received earlier.
- Issues for electronic unit control average readings that allow the engine to operate normally.
Firmware of the electronic control unit
Most effective way- this is to completely change the program embedded in the control unit. The essence of the entire procedure is to get rid of completely or partially any reaction to changes in readings coming from the oxygen sensor. But please note that this will void the warranty on the car. Therefore, for new cars this method, like any other, will not work.
Conclusion
And most importantly, think about whether the game is worth the candle? Is it even necessary to make such a part as a lambda probe decoy with your own hands? "Lancer 9", let's say, is far from a budget car, but a high-class one, so is there any point in violating its design with various homemade products? Is this reasonable? If you have money for an expensive car, then you should also have money to maintain it in working condition. If not, then why did you buy such a car?
I found this program on the Internet. Has anyone tried it? So, what are your thoughts on this program? Description and screenshots below
Gas analyzer based on the transmission coefficient of infrared rays through a filter film. This primitive method of measuring the percentage of CO2 in engine exhaust produces a large error, but is easy to manufacture. Factory-made gas analyzers that accurately determine CO2 content cost about $300, and you can assemble this yourself from simple parts. After manufacturing, setting up and testing this gas analyzer, the differences in measurements with the real one turned out to be about 0.5% in one direction or another.
To simplify the manufacture of the gas analyzer, the entire calculation part, setting and display of the result is done using the program method.
Diagram of assembly and connection of the gas analyzer to the computer.
Making a filter
The most difficult thing in manufacturing will be to make a filter film, which will only need to transmit those infrared rays that have been refracted by Carbon dioxide (CO2). To make the film you need:
1. 2 grams of potassium permanganate
2. Aluminum powder 0.5 grams
3. Epoxy resin (Already diluted with hardener) transparent color 10 grams.
All this is mixed in a large container and applied to ordinary glass. The thickness of the cured film should be 0.2 mm
Other components
Remember that the diode must be infrared, it is not difficult to find, distinctive features, it is white. When it lights up it has no glow. (In everyday life, such diodes are installed in remote controls).
Phototransistors look different, the main thing is that it has an operating frequency range of received radiation that is the same as that of an infrared LED. Please come to any radio store and say give me an infrared optocoupler (infrared LED and phototransistor).
Since our circuit is quite primitive, it will be very sensitive to temperature changes and for greater accuracy a temperature sensor is included. This circuit uses a temperature measurement sensor from a regular Tester DT-838 DIGITAL MULTIMETER (a regular cheap “tseshka” for 200 rubles). Of course, you can use a thermistor or a thermistor as a sensor, but then you can get large deviations since in this circuit testing and adjustment were carried out specifically with a temperature sensor from the “tseshka”.
Data processing
Next, after connecting the device to the computer, launch the “FRIZO Gas Analyzer” program. Select the COM port to which everything is connected and click Start; if the sensor operates successfully, the program will show that the connection has been established.
Congratulations on the successful assembly, installation and configuration of the gas analyzer, you can now install the sensor in exhaust pipe vehicle to measure the percentage of CO2 in the exhaust gases. Remember that the accuracy of the device is +-0.5%.
Hi all! In this article I will tell you how to make a simple gas leak sensor with your own hands from available parts.
Probably, now even any schoolchild knows that such a dangerous gas as methane has no odor, and it is simply impossible to detect it in the air without special instruments. Methane is the main component of natural gas. Methane is the same gas that flows through pipes and in your home, with the slight change that odorous additives are specially added to it so that it can be detected by humans using the sense of smell.
But if you can smell it, then why make a sensor, you ask? The fact is that a person can smell an already dangerous concentration of gas. The sensor has higher sensitivity. And if there is a small gas leak in the room for several hours, this concentration may not have an odor, but there will be a 100% danger of explosion. To avoid this and detect small concentrations of gas in the air, gas presence sensors are used.
This, of course, is most likely a test project that shows the basic principle of working with a gas sensor, but no one in the future will stop you from improving it and making it a serious project.
I will provide a list of parts and materials that are needed to build our sensor. (Link to store)
1. .
2. 9V battery and connector.
3. .
4. .
5. .
6. (any n-p-n structure is suitable).
7. .
8. .
9. .
10. .
11. Other materials such as soldering iron, solder, flux and wires.
So let's start setting up this project!
The scheme is quite simple. Its heart is the MQ-02 gas sensor, but you can also use MQ-05, MQ-04 sensors.
MQ-02– propane, methane, alcohol vapor, hydrogen, smoke react. The MQ-02 gas sensor is a complete module. It has an amplifier and a variable resistor on the board, with which you can adjust the sensitivity.
My circuit consists of a multivibrator assembled on a “555” timer chip.
