Homemade gas analyzer. Homemade CO2 gas analyzer for cars. Oxygen sensor design features

The gas analyzer is an electro-optical device for measuring the volume fraction of components in engine exhaust gases.

Gas analyzers are 1,2,3,4,5-component. Measured components exhaust gases: CO, CH, CO2, O2, NOx. We know that all modern gasoline cars (with the exception of cars with direct injection of fuel into the cylinders and stratified distribution of the mixture) in steady conditions (except for full load) must 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 assess 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 will be correct to use 4 and 5-component gas analyzers, moreover, those that are able to calculate the Lambda coefficient.

The 4-component gas analyzer is irreplaceable for autodiagnostics. 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, if possible, be completely combusted in the engine so that the maximum possible engine power can be achieved with low fuel consumption and the resulting pollutants are kept as low as possible from the outset. Absolutely perfect combustion is not possible even with perfect air fuel mixture, since the time available for this is too short, even with the best design and optimal control of all components important for combustion. From a theoretical point of view, combustion would be perfect with a fuel to air ratio of 1: 14.7 or, in volume terms, 1 liter of fuel mixed with 10,000 liters of air. This ratio is denoted by lambda.

The analyzed gas enters the analyzed cuvette, where the determined components, interacting with the radiation, cause its absorption in the corresponding spectral ranges. Radiation fluxes from characteristic spectral regions are isolated by interference filters and converted into electrical signals proportional to the concentration of the analyzed components. The electrochemical sensor, when interacting with oxygen, generates a signal proportional to the oxygen concentration. The l value is calculated by the gas analyzer automatically from the measured CO, CH, CO2 and O2.

Modern high-end gas analyzers, in addition to reliability and ease of use, have many additional functions. They can measure the speed 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 a gas analyzer from the point of view of an operator is its reliability. Since, by 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 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 preliminary preparation unit gases.

Found on the internet just such a program. Has anyone tried it? Well, 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 the exhaust of an engine gives a large error, but is easy to manufacture. Factory gas analyzers with high accuracy determining the CO2 content cost about $ 300, and you can assemble this yourself from simple parts. After the manufacture, adjustment and testing of this gas analyzer, the discrepancy in measurement with the present one turned out to be about 0.5% in one direction or another.

For ease of manufacturing a gas analyzer, the entire calculation part, setting and displaying the result is done by the programs using the method.

Diagram of assembly and connection of the gas analyzer to the computer.

Filter making

The most difficult thing in the manufacture will be to make a filter film, which will have to transmit only those infrared rays that have been refracted by Carbon dioxide (CO2). To make a film, you must:

1.2 grams of potassium permanganate

2. Aluminum powder 0.5 grams

3. Epoxy resin (already diluted with hardener) transparent 10 grams.

All this is mixed in a small 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, easy to find, distinguishing features, it is white. when lit, 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 the received radiation is the same as that of an infrared LED. You just have to come to any radio store and say give me an infrared optocoupler (infrared LED and phototransistor).

Since our circuit is rather primitive, it will be very sensitive to temperature changes and a temperature sensor is introduced for greater accuracy. This circuit uses a temperature measurement sensor from a conventional DT-838 DIGITAL MULTIMETER Tester (a usual cheap "tseshka" for 200 rubles). Of course, you can use a thermistor or thermotransistor as a sensor, but then you can get large deviations, since in this circuit testing and adjustment was carried out with a temperature sensor from the "shop".

Data processing

Then, after connecting the device to the computer, launch the "FRIZO Gas Analyzer" program. Select the COM port to which everything is connected and press Start, if the sensor is working successfully, 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 of the car to measure the percentage of CO2 in the exhaust gas. Remember that the accuracy of the device is + -0.5%.

From the article you will learn how the lambda probe snag is made with your own hands and whether it is worth installing it on your car. The efficiency of the engine depends on how well the air-fuel mixture burns. It is very important to choose the optimal proportion of gasoline and air content depending on the engine load.

If in old cars all the settings for the quality and quantity of fuel depended on the carburetor adjustments, then in modern cars the situation is somewhat different. Everything is placed in the reliable hands of microprocessor technology and a huge number of sensors.

How does the fuel injection system work?

There are several of the most important units that are in the injection system:

1. Fuel tank.
2. fuel in one housing with pump and filter.
3. Fuel rail (installed in the engine compartment on the intake manifold).
4. Injectors that supply the gasoline mixture to the combustion chambers.
5. Control block. As a rule, it is mounted in the passenger compartment and allows you to control the supply of the air-fuel mixture.
6. Exhaust system, which ensures the complete destruction of harmful substances.

It is in the latter that the lambda probe snag is installed. With your own hands ("Lancer 9" or "Lada" you have, it doesn't matter) you can make it quite simply. But you should also be aware of all the consequences of installing a "stub". Do-it-yourself lambda probe spoofing on the Priora can be made with a simple design, in any case it will have a significant effect on engine operation.

How many sensors are in the car

Mounted in the exhaust system modern cars with fuel injection system. 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 exit from 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 functioning of the lambda probe

All automotive electronics, which are responsible for the correct formation of the mixture, are involved in the distribution of fuel to the injectors. With the help of an oxygen sensor, the required amount of air is determined to form a high-quality mixture. Thanks to the fine tuning of the lambda probe, it is possible to achieve a high degree of environmental friendliness and economy.

The fuel burns out completely, at the exit from the pipe there is practically clean air - this is a plus for the environment. The most accurate dosage of air and gasoline is a benefit 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, the replacement will cost a pretty penny. Therefore, the thought arises: "But there is a snag of a lambda probe, it will not be difficult to make it with your own hands (the VAZ-2107 even needs to replace the oxygen sensor)."

Oxygen sensor design features

The appearance of this device is simple - a long electrode-body, from which wires extend. The case is platinum-plated (it was this precious metal that was discussed above). But the internal structure is more "rich":

1. A metal contact that connects the wires for connection with an active electrical element of the sensor.
2. Dielectric seal for safety. It has a small hole through which air enters the inside of the case.
3. Zirconium electrode of hidden type, 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.
4. Protection screen with a hole for exhaust gas outlet.

Sensor types

There are two main types of oxygen sensors that are used in automotive technology today:

1. Broadband.
2. Two-point.

Regardless of the type, they have an almost identical internal structure. External similarities, as you know, are also there. But the principle of operation is significantly different. The broadband oxygen sensor is an upgraded point-to-point sensor.

It contains a pumping component, which, due to voltage fluctuations, sends a signal to the electronic control unit. The supply of current 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 a lambda probe snag is made and installed with your own hands. "Chevrolet Lanos", for example, works stably with it and does not give errors after refueling with bad gasoline.

Oxygen sensor malfunction detection

Of course, this element does not last forever, despite its high cost and platinum in the composition. Of course, the lambda probe is no exception, and at one point it can order to live a long time. And some symptoms will appear:

1. The level of CO content in the exhaust gases rises 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. Determine the content of harmful substances only with the help of gas analyzers. But for personal purposes it is unprofitable to acquire it.
2. Pay attention to on-board computer... See what the current gas mileage is. This is the easiest way. You can also judge by the frequency of refueling.
3. And the last sign is the burning on dashboard a lamp signaling the presence of malfunctions in the engine.

If it is not possible to analyze the exhaust gas using a special device, it can be done visually. Light smoke is a sign that there is too much air in the fuel mixture. Black, on the other hand, speaks of a large amount of gasoline. Therefore, it is possible to judge that the system is not working properly. But the picture is different if there is a lambda probe blende. With our 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 in the epicenter of fuel combustion. Consequently, the composition of gasoline has a significant effect on the operation of the lambda probe. If gasoline contains a lot of impurities, does not comply with GOST, of poor quality, then the oxygen sensor will give 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 disrupts its functioning. But there may be other reasons for breakdowns:

1. Mechanical impact- vibrations, too active operation of the car, lead to damage or burnout of the case. It is impossible to carry out repairs or restoration, the rational way out is to buy a new one and install it.
2. Incorrect operation of the fuel supply system. If the air-fuel mixture does not completely burn out, then the soot begins to settle on the lambda probe housing, and also enters through the air inlets. Of course, cleaning the device helps at first. But if it needs this procedure more and more often, then it will have to install a new device.

Try to diagnose your car from time to time. In this case, you will not be surprised by the failure of any element.

Troubleshooting

Of course, the most accurate answer about breakdowns will be given only by diagnostics on specialized equipment. But it is possible to identify the breakdown of the sensor on your own, it is enough to read carefully about the features of the sensor and its characteristics. But the lambda probe snag is rarely installed. With your own hands (VAZ-2114 or any other car if you have), you can literally make a snag plug from available tools. The troubleshooting algorithm is as follows:

1. Open the hood and find the exhaust manifold. Work must be carried out on a cooled engine, as you can get serious injuries. Find the lambda probe on the catalytic converter.
2. Spend visual inspection... Contamination, soot, light deposits are signs of improper operation of the fuel system. Moreover, the last sign suggests that there is too much lead in gases.
3. Replace the oxygen sensor and re-diagnose the entire fuel system. If there is no contamination, you need to continue troubleshooting.
4. 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 to the value 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 sensor breakdown.

You can also judge the breakdown by other characteristics. Create an artificial vacuum in the vacuum tube. 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 carry out a regular technical inspection. For example, a lambda probe needs to be inspected every 30 thousand kilometers. Moreover, he has no more than a hundred thousand resource - 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 blende suitable for your car? You can make such a device with your own hands on "Kalina" 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 the gasoline that is sold at his favorite gas station. But who knows what kind of gasoline is bottled there? Therefore, try to trust “branded” gas stations that value their name. But if there are no good gas stations nearby, then you will have to be content with what is nearby. And a burning ICE error lamp is a frequent occurrence, which will help to get rid of the installation of a trick.

Homemade blende device

It all depends on what means you have. It is worth noting that the lambda probe blende with your own hands at the 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, since it has a very high resistance to heat. Moreover, the dimensions of this blank should 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 the catalyst layer is applied. Due to this, it passes through a thin hole and is oxidized by crumb. The result is a significant reduction in CO levels. Hence, the standard oxygen sensor is being fooled. But such devices can be installed on budget cars... More expensive cars should not be altered.

Electronic snag

But if you have the skills to install electrical circuits, you can make homemade device... You only need one of these two elements - a resistor or a capacitor. But such a lambda probe trick is not suitable for everyone. With your own hands ("Subaru Forester" or VAZ, it doesn't matter) you can make it according to one of the proposed options. But be careful, because a misunderstanding of the work of the trick will affect the functioning of the entire control unit. And if you are not sure, it is better to get a ready-made one on a microcontroller. She is good in that she can independently carry out the following actions:

1. Estimate the gas concentration at the first sensor.
2. Next, an impulse is formed, which corresponds to the signal that was received earlier.
3. Provides averaged readings for the electronic control unit, which allow the engine to operate normally.

Electronic control unit firmware

The most effective way is to completely change the program in the control unit. The essence of the whole procedure is to get rid of all or part of any reaction to a change in the readings from the oxygen sensor. Note, however, that the warranty will be void on the vehicle. 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? Do I need to do such a detail as a lambda probe snag with my own hands? "Lancer 9", for example, is not a budget car, but a high-end one, so is there any point in breaking 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 order. If not, why did you buy such a car?

Hello everyone! In this article, I will tell you how to make a simple DIY gas leak detector from the 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 and in your home, with the slight change that smelling 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 have an odor, but there will be a 100% explosion hazard. To avoid this and track beginners to small concentrations of gas in the air and 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 in the future will prevent you from improving and making a serious project out of it.
I will provide a list of parts and materials that are required to build our sensor. (Store link)
1. .
2. 9V battery and connector.
3. .
4. .
5. .
6. (any structure n-p-n will do).
7. .
8. .
9. .
10. .
11. Other materials such as soldering iron, solder, flux and wires.

So let's get started setting up this project!

The circuit is pretty simple. Its heart is the gas sensor MQ-02, but you can also use the sensors MQ-05, MQ-04.

MQ-02- propane, methane, alcohol vapors, hydrogen, smoke react. Gas sensor MQ-02 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.

A simple automotive one-component gas analyzer is designed to measure the content of only carbon monoxide CO in the exhaust gases, mainly uses the method of afterburning incompletely burnt components in the exhaust gases. Afterburning of CO is performed in the measuring chamber of the device using a special heated filament, while the change in filament temperature 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 - 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 cuvette (chamber); 7 - source of infrared radiation; 8 - synchronous motor; 9 - obturator; 10 - comparative cuvette (chamber) CO; 11 - infrared CO receiver; 12 - membrane condenser; 13, 16 - amplifiers; 14 - comparative cuvette (chamber) C n H m; 15 - infrared receiver С n Н m; 17, 19 - indicators of the content of hydrocarbons and CO; 18 - measuring cuvette (chamber) С n Н m

Determination of the content of harmful substances in exhaust gases with modern multicomponent gas analyzers for a car 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 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 luminous flux that passes through the gas. Molecules of any gas represent 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 luminous flux, which is called the absorption maximum of the given gas, will be absorbed. Moreover, 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, the fact that different gases correspond to different absorption maxima makes it possible. Thus, the concentration of each of the gases in the engine exhaust can be determined by measuring the decrease in the intensity of the luminous flux in that part of the spectrum that corresponds to the absorption maximum of a particular gas.

The spectrometric unit of the device works as follows:

Exhaust gases, previously filtered and free from soot and moisture, are pumped through the measuring cuvette, which is a tube with ends closed with optical glass. On one side of the tube, a radiator is installed, which is a spiral heated by an electric current, the temperature of which is strictly stabilized at one mark. Such an emitter generates a stable flow 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 under study. The stream, after passing through the light filters, enters an infrared receiver, which measures the intensity of this stream and converts it into information on the concentration of gases in the vehicle's exhaust.

Since this method is applicable only for measuring the concentration of CO 2, CO and CH, then at the next stage, the mixture of exhaust gases from the measuring cuvette is sequentially fed to electrochemical sensors for measuring oxygen O 2 and nitrogen oxides NO X. At the same time, 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. Signals from the spectrometric unit and electrochemical sensors in a modern gas analyzer are processed using a microprocessor-based 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 low, and therefore it is inconvenient to use percentages to indicate their amount.

The ratio between percentage and ppm can be described by the following equality:

So, for example, in the exhaust gases of a conventional engine internal combustion of a passenger car, the CH content is about 0.001% -0.01%. The difficulty of using such values ​​in work has predetermined the mass distribution of ppm as a unit of concentration.

A gas analyzer is a complex instrument, 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 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 block walls, lead to a noticeable scatter in the readings of the spectrometric block, and ultimately to its breakdown. Therefore, before entering the measuring unit, the exhaust gases must undergo special training, 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 with a moisture separator, which can have a wide variety of designs. At this stage, moisture droplets are separated from the gas stream and then removed, which condense on the inner surfaces of the probe and the connecting hose. Removal of condensate from the storage tank is performed 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 carried out. Filters fine cleaning there may be several, while they are installed sequentially one after another.