The gas analyzer is an electron-optical device for measuring the volume fraction of components in the exhaust gases of an engine.
Gas analyzers are 1,2,3,4,5-component. Measured exhaust gas components: CO, CH, CO2, O2, NOx. We know that all modern petrol cars(with the exception of vehicles with direct fuel injection into the cylinders and layered distribution of the mixture) in steady state conditions (except for full load mode) must operate at a stoichiometric air / fuel ratio (Lambda is 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 able to calculate the Lambda coefficient.
A 4-component gas analyzer is indispensable for an autodiagnostician. It helps to look inside the combustion chambers of a running engine and determine how the combustion process of the fuel-air mixture is going. This mixture should, as far as possible, be completely burned in the engine so that the maximum possible engine power can be achieved with low fuel consumption and the resulting harmful substances can be kept as low as possible from the outset. Absolutely perfect combustion is impossible even with ideal air-fuel mixture, because 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 weight ratio of fuel and air of 1:14.7, or, in terms of volume, 1 liter of fuel mixed with 10,000 liters of air. This ratio is called lambda.
The analyzed gas enters the analyzed cuvette, where the determined components, interacting with the radiation, cause its absorption in the corresponding spectral ranges. The radiation fluxes of the characteristic regions of the spectrum are separated by interference filters and converted into electrical signals proportional to the concentration of the analyzed components. An electrochemical sensor, when interacting with oxygen, 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 high-class gas analyzers, in addition to reliability and ease of use, have many additional features. They can measure RPM crankshaft engine, oil temperature, as well as memorize intermediate measurement protocols and transfer the results to a personal computer or print them on the built-in printer.
A very important quality of the gas analyzer from the point of view of the operator is its reliability. Since, according to its design, a gas analyzer is a complex electronic device, it is usually impossible to repair it on its own and you have to contact a company 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 preliminary preparation unit gases.
A simple automotive one-component gas analyzer is designed to measure the content of 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 thread, while the temperature change of the thread characterizes the CO content in gases. The accuracy of the readings of such a gas analyzer is low and depends largely on the content of another component - hydrocarbon CH.
Figure 3. Schematic diagram of a two-component gas analyzer for CO and hydrocarbons
1 - probe; 2...4 - filters; 5 - exhaust gas pump; 6 - measuring cuvette (chamber); 7 - source of infrared radiation; 8 - synchronous motor; 9 - obturator; 10 - comparative cuvette (chamber) CO; 11 - infrared receiver CO; 12 - membrane capacitor; 13, 16 - amplifiers; 14 - comparative cuvette (chamber) C n H m ; 15 - infrared receiver C n H m; 17, 19 - indicators of the content of hydrocarbons and CO; 18 - measuring cuvette (chamber) С n Н m
The determination of the content of harmful substances in exhaust gases by modern multi-component gas analyzers for a car is carried out without the use of chemical reagents, mainly by thermal (infrared) measurement. The method is based on the principle of measuring the amount of 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 an oscillatory system that is capable of absorbing infrared radiation only in a strictly defined wavelength range. Thus, if a stable infrared stream 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. In this case, the higher the gas concentration in the flask, the greater the absorption will be observed.
To measure 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, it is possible to determine the concentration of each of the gases in the engine exhaust 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 particular gas.
The spectrometric unit of the instrument works as follows:
Through the measuring cuvette, which is a tube with closed optical glass ends, exhaust gases are pumped, previously filtered and cleaned of soot and moisture. On one side of the tube, an emitter is installed, which is a spiral heated by electric current, the temperature of which is strictly stabilized at one mark. Such an emitter generates a stable stream of infrared radiation.
On the other side of the measuring cuvette, light filters are installed, which separate those wavelengths from the entire radiation flux that correspond to the absorption maxima of the studied gases. The flow, after passing through the filters, enters the infrared radiation receiver, which measures the intensity of this flow and converts it into information about the concentration of gases in the car's exhaust.
Since this method is applicable only for measuring the concentration of CO 2 , CO and CH, at the next stage the mixture of exhaust gases from the measuring cuvette is sequentially fed to electrochemical type sensors for measuring oxygen O 2 and nitrogen oxides NO X . In this case, electrochemical sensors generate 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 - by the psychrometric method, O 2 and NO X - by electrochemical sensors. The processing of signals from the spectrometric unit and electrochemical sensors in a modern gas analyzer is performed using a microprocessor electronic circuit.
After processing the signals, information about the content of gases is displayed on the screen of the device: 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 amount.
The relationship between percentages and ppm can be described by the following equation:
So, for example, in the exhaust gases of a conventional engine internal combustion passenger car CH content is about 0.001%-0.01%. The complexity of using such values in the work predetermined the mass distribution of ppm as a unit of concentration designation.
The gas analyzer is a complex device, the quality of which is primarily determined by the accuracy and reliability of the spectrometric unit. The spectrometric unit is the most complex and expensive part 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 unit, lead to a noticeable spread in the readings of the spectrometric unit, and ultimately to its failure. Therefore, before getting into the measuring unit, the exhaust gases must undergo special preparation, which usually consists of several stages:
rough cleaning of exhaust gases. It is carried out using a filter, which is installed at the inlet to the device, or directly in the sampling 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, moisture drops are separated from the gas flow, and then moisture drops are removed, which condense on the internal surfaces of the probe, as well as the connecting hose. Removal of condensate from the accumulator is carried out either automatically or manually by the operator.
fine filtration. With the help of a fine filter, the final filtration of the smallest mechanical particles is performed. There can be several fine filters, while they are installed sequentially one after another.
From the article you will learn how a do-it-yourself lambda probe snag is made and whether it is worth installing it on your car. How well the air-fuel mixture burns in the engine depends on its coefficient useful action. It is very important to choose the optimal proportion of the content of gasoline and air, depending on the load on the engine.
If in old cars all the settings for the quality and quantity of fuel depended on the adjustments of the carburetor, then in modern cars the situation is somewhat different. Everything is given into the reliable hands of microprocessor technology and a huge number of sensors.
How does an injection system work?
There are several most important nodes that are available in the injection system:
- Fuel tank.
- fuel in one housing with a pump and a 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 passenger compartment 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 snag of the lambda probe is installed. With your own hands ("Lancer 9" or "Lada" you have, it doesn't matter) you can make it quite simply. But one should also be aware of all the consequences of installing a "stub". Do-it-yourself lambda probe snag on the Priora can be made of a simple design, in any case, it will have a significant impact on engine operation.
How many sensors are in the 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, then it is located after the catalytic converter. If two, then before and after.
Moreover, one measures the percentage of oxygen immediately at the outlet of the cylinders and sends its signal to the electronic control unit. The second, which is mounted after the catalyst, is necessary to correct the readings of the first.
The principle of operation of the lambda probe
All automotive electronics, which is responsible for the correct formation of the mixture, is involved in the distribution of fuel to the injectors. Using an oxygen sensor, the required amount of air is determined in order to form a high-quality mixture. Thanks to the fine adjustments of the lambda probe, a high degree of environmental friendliness and economy can be achieved.
The fuel burns completely, at the outlet of the pipe there is almost clean air - this is a plus for the environment. The most precise dosage of air and gasoline is a gain in fuel economy. Of course, coupled 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, the replacement will cost a pretty penny. Therefore, the thought arises: “But there is a snag of a lambda probe, with your own hands (VAZ-2107 even needs to replace the oxygen sensor), it will not be difficult to make it.”
Design features of the oxygen sensor
The appearance of this device is simple - a long electrode-case, from which wires extend. The case is coated with platinum (it was this precious metal that was discussed above). And here internal organization more "rich"
- A metal contact that connects wires to connect to an active electrical element sensor.
- Dielectric seal for safety. It has a small hole through which air enters the case.
- Hidden type zirconium electrode, which is located inside the ceramic tip. When current flows through this electrode, it heats up to a temperature in the range of 300 ... 1000 degrees.
- Protective screen with exhaust outlet.
Sensor types
The two main types of oxygen sensors currently used in automotive technology are:
- Broadband.
- Point-to-point.
Regardless of the type, they have an almost identical internal structure. External similarities, as you know, also exist. But the principle of operation is significantly different. The broadband oxygen sensor is an upgraded point-to-point.
It has a pumping component, which, due 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 concentration of CO in the exhaust gas is measured. But sometimes a do-it-yourself lambda probe snag is made and installed. Chevrolet Lanos, for example, works stably with it and does not give errors after refueling with bad gasoline.
Determination of malfunction of the oxygen sensor
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 fine moment it can order a long life. And there will be some symptoms:
- The level of CO content in the exhaust gases increases sharply. If an oxygen sensor is installed on the car, and the CO level is extremely high, then this indicates that the control device is out of order. It is possible to determine the content of harmful substances only with the help of gas analyzers. But for personal purposes, it is unprofitable to acquire it.
- Sharply pay attention to on-board computer. Look at your current gas mileage. This is the easiest way. You can also judge by the frequency of fillings.
- And the last sign is a fire on dashboard a lamp that indicates 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 is possible to judge the incorrect operation of the system. But the picture is different if there is a snag of a lambda probe. With your own hands ("Volkswagen", VAZ, "Toyota" - for any car), such a device is made quite simply.
Causes of breakdowns
It is worth paying attention to the fact that the oxygen sensor is located at the epicenter of fuel combustion. Therefore, the composition of gasoline has a significant impact on the operation of the lambda probe. If gasoline contains a lot of impurities, does not meet GOST, is of poor quality, then the oxygen sensor will give an error or an incorrect signal to the electronic control unit. AT worst case the device is out of order. And this happens due to the high content of lead, which is deposited on the sensor and disrupts its functioning. But there may be other reasons for breakdowns:
- Mechanical impact- vibrations, too active operation of the car, lead to damage or burnout of the body. It is impossible to repair or restore, the rational way out is to buy a new one and install it.
- Incorrect operation of the fuel supply system. If the air-fuel mixture does not completely burn out, then soot begins to settle on the body of the lambda probe, and also enters 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, the failure of any element will not be a surprise for you.
Troubleshooting
Of course, only diagnostics on specialized equipment will give the most accurate answer about breakdowns. But you can also identify a breakdown of the sensor yourself, just read carefully about the features of the sensor and its characteristics. But the lambda probe snag is installed extremely rarely. With your own hands (VAZ-2114 or any other car if you have one), you can literally make a fake plug from improvised means. The troubleshooting algorithm is as follows:
- Open the hood and find exhaust manifold. It is necessary to carry out work on a cooled engine, as serious injuries can be caused. Find on catalytic converter the Lambda probe.
- Do an external inspection. Pollution, soot, light coating are signs of incorrect operation of the fuel system. Moreover, the last sign suggests that there is too much lead in the gases.
- Replace the oxygen sensor and diagnose all fuel system again. If no contamination is observed, continue troubleshooting.
- Disconnect the sensor plug and connect a voltmeter with a scale of up to 2 Volts to it. Start the engine and increase the rpm to 2500 rpm, then decrease it down to idle move. The change in voltage 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 sensor failure.
You can also judge the breakdown by other characteristics. In a vacuum tube, artificially create a vacuum. In this case, the voltage should be very low - less than 0.2 volts.
Oxygen sensor resource
To ensure the smooth and stable operation of the car, you need to regularly conduct a technical inspection. For example, a lambda probe needs to be inspected every 30 thousand kilometers. Moreover, it has a resource of 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 - is the lambda probe snag suitable for your car? With your own hands on Kalina, you can make such a device in a few minutes.
But there is one caveat. The motorist cannot guarantee that the fuel with which he fills the car is of high quality. Of course, everyone is used to filling up the gasoline that is sold at his favorite gas station. But who knows what the composition of the gasoline that is poured there is? Therefore, try to trust the “brand” gas stations that value their name. But if not around good gas stations, you will have to be content with what is at hand. And a burning ICE error lamp is a frequent occurrence, which installation of a snag will help get rid of.
Homemade trick device
It all depends on what resources you have. It is worth noting that do-it-yourself lambda probe snag on a VAZ can be the most democratic, it still works flawlessly. Most cheap option- homemade. The body is made of bronze. This metal is better to choose, since 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. In fact, 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 catalyst layer is applied. Due to this, it passes through a thin hole and is oxidized by the crumb. The result is a significant reduction in CO levels. Therefore, the standard oxygen sensor is deceived. But such devices can be installed on budget cars. More expensive cars should not be modified.
Electronic snag
But if you have installation skills electrical circuits, can be made homemade device. You will need only one of these two elements - a resistor or a capacitor. But such a blende of a lambda probe is not suitable for everyone. With your own hands ("Subaru Forester" or VAZ, it does not matter), you can make it according to one of the proposed options. But be careful, because a misunderstanding of the blende operation 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. She is good in that she can independently carry out the following actions:
- Estimate the gas concentration at the first sensor.
- Next, the pulse is formed, which corresponds to the signal that was received earlier.
- Gives average readings for the electronic control unit, which allow the engine to work normally.
Firmware of the electronic control unit
The most effective way is to completely change the program embedded in the control unit. The essence of the whole procedure is to get rid, in whole or in part, of any reaction to a change in the readings coming from the oxygen sensor. But pay attention to the fact that the warranty is lost on the car. Therefore, for new machines, this method, as well as 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 detail as a snag of a lambda probe with your own hands? "Lancer 9", let's say, the car is far from being a budget car, but a high-class car, so is there any point in violating its design with various homemade products? Is it reasonable? If there is money for an expensive car, then there must be funds to maintain it in working condition. If not, then why did you buy such a car?
Hello! In this article, I will tell you how to make a simple do-it-yourself gas leak sensor from available parts.
Probably, now even any schoolchild knows that such a dangerous gas as methane has no smell, and it is simply not possible to detect it in the air without special devices. Methane is the main component of natural gas. Methane, the same gas that flows through the pipes in your home, with the slight modification that odor additives are specially added to it so that it can be detected by a person 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 a higher sensitivity. And if there is a small gas leak in the room for several hours - this concentration may not smell, but there will be a 100% explosion hazard. To avoid this and to find the direction of small concentrations of gas in the air, beginners use gas sensors.
This, of course, is most likely a test project that shows the basic principle of working with a gas sensor, but no one further will prevent you from improving and making a serious project out of it.
I will give 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. (suitable for any n-p-n structure).
7. .
8. .
9. .
10. .
11. Other materials such as soldering iron, solder, flux and wires.
So, let's start setting up this project!
The circuit is pretty simple. Its heart is the MQ-02 brand gas sensor, but you can also use the MQ-05, MQ-04 sensors.
MQ-02- propane, methane, alcohol vapors, hydrogen, smoke react. The MQ-02 gas sensor is a complete module. He 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.
Found this software on the internet. Has anyone tried it? Well, what are your thoughts on this program? Description and screenshots below
Gas analyzer based on the coefficient of transmission of infrared rays through the filter film. This primitive method of measuring the percentage of CO2 in an engine's exhaust yields a large error, but is easy to manufacture. Factory gas analyzers with high precision those that measure CO2 cost about $300, and you can assemble this yourself from simple parts. After the manufacture, adjustment and testing of this gas analyzer, the discrepancies in measurement with the real one turned out to be about 0.5% in one direction or another.
For ease of manufacture of the gas analyzer, the entire calculation part, tincture and display of the result is done by the programs by the method.
Scheme of assembling and connecting the gas analyzer to a computer.
Filter manufacturing
The most difficult thing in manufacturing will be to make a filter film, which will have to pass only those infrared rays that have been refracted by Carbon dioxide (CO2). To make a 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 the largest 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 easy to find, distinctive features, it is white. when lit, it does not have any glow. (In everyday life, such diodes are placed 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 a temperature sensor has been introduced for greater accuracy. This circuit uses a temperature measurement sensor from a conventional Tester DT-838 DIGITAL MULTIMETER (the usual cheap "tseshka" for 200 rubles). Of course, you can use a thermistor or a thermotransistor as a sensor, but then you can get large deviations, since in this circuit testing and tuning was carried out precisely with a temperature sensor from the "shop".
Data processing
Further, after connecting the device to the computer, we launch the "FRIZO Gas Analyzer" program. We select the COM port to which everything is connected and press Start, if the sensor is successful, the program will show that the connection has been established.
Congratulations on the successful assembly, installation and configuration of the gas analyzer, now you can install the sensor in exhaust pipe car to measure the percentage of CO2 in the exhaust gases. Remember that the accuracy of the device is + -0.5%.