Background:

Carbon dioxide is a gaseous compound produced by the reaction of carbon and oxygen. Its chemical formula is CO2. A carbon dioxide molecule consists of two oxygen atoms and one carbon atom. Carbon dioxide is an inorganic substance that is not flammable and generally does not support combustion. It is non-toxic at low concentrations, but when the concentration of carbon dioxide in the environment exceeds a certain amount, carbon dioxide will have an impact on the human body. We can use carbon dioxide detector to monitor.This article explains in detail how to measure carbon dioxide?

Why measure Carbon Dioxide?

As we said, carbon dioxide at room temperature is a colorless, odorless gas that cannot be detected by the senses. Low concentrations of carbon dioxide are not toxic, while high concentrations of carbon dioxide can poison animals. Also, carbon dioxide is very harmful to the environment and it is the main cause of the greenhouse effect.

Greenhouse gases such as carbon dioxide in the atmosphere can radiate long-wave radiation with longer wavelengths to the ground after absorbing the long-wave radiation on the ground, which has a thermal insulation effect on the ground. When the temperature continues to increase, it leads to global warming. In addition, human activities will emit a large amount of carbon dioxide, resulting in a sharp increase in the concentration of greenhouse gases in the atmosphere, resulting in an increasing greenhouse effect. By measuring the amount of carbon dioxide (CO2) in the environment, timely action and preventive measures can be taken to reduce the concentration of carbon dioxide in the atmosphere.

In agriculture, carbon dioxide is one of the raw materials for green plants to carry out photosynthesis, and 95% of the dry weight of crops comes from photosynthesis. Therefore, the use of carbon dioxide sensors to control the concentration has become an important factor affecting crop yield. For example, in greenhouse planting, the level of carbon dioxide concentration will affect the growth quality of crops.

Industrially, solid carbon dioxide is commonly used to refrigerate frozen foods and other perishable foods in transit, and as a refrigerant in many industrial processes. Gaseous carbon dioxide is commonly used in carbonated beverages, pH control in water treatment processes. In the medical industry, it is also used as a diluent for bactericidal gas. Achieving this all requires need to measure carbon dioxide (CO2).

How is Carbon Dioxide (CO2) measured?

Carbon dioxide sensors are the most commonly used tools to measure carbon dioxide (CO2) concentrations. The carbon dioxide concentration is detected by the measuring unit and converted into a digital display to the user. There are three main types of carbon dioxide (CO2) sensors: electrochemical sensors, non-dispersive infrared (NDIR) sensors, and metal oxide semiconductor (MOS) sensors.

Electrochemical Sensors

Electrochemical gas sensor is a detector that allows gas to be oxidized or reduced at the electrode to measure the current and obtain the gas concentration. When the gas diffuses into the working electrode of the sensor, the gas is oxidized or reduced, and this electrochemical reaction generates a current flowing through the external circuit, and the gas concentration is converted by measuring the current value. In addition to measurement, amplification and other signal processing are performed, and the external circuit maintains the voltage across the sensor and the voltage of a two-electrode back-referenced sensor. An opposite reaction occurs at the counter electrode. Thus, if the working electrode is oxidizing, the opposite electrode is reducing.

The magnitude of the current depends on how much carbon dioxide is oxidized at the electrodes. The sensor is designed so that the gas supply is diffusion limited and the sensor has a linear output proportional to the gas concentration. Linear output is one of the advantages of electrochemical sensors over other technology sensors.

Non-Dispersive Infrared (NDIR) Sensors

Different elements on Earth absorb certain types of light. For example: green reflects green light but absorbs light of other colors. Our eyes cannot see this process. When elements are broken down into atoms and molecules, we can know exactly what kind of light they each absorb, even light that our eyes can’t see. That’s how NDIR sensors work! The principle of non-divergent infrared gas sensors is that various gases absorb light. And different gases absorb light of different wavelengths, such as CO2 is most sensitive to infrared (wavelength of 4.26 m).

The light passes through the carbon dioxide gas in the optical path, passes through the filter, and reaches the infrared detector. The concentration of carbon dioxide (CO2) is determined by measuring the intensity of infrared light from the infrared sensor. When there is no carbon dioxide (CO2) in the environment, its intensity is the strongest. When carbon dioxide (CO2) enters the gas chamber, carbon dioxide absorbs part of the infrared light, so that the light intensity reaching the detector is weakened. The concentration of carbon dioxide can be calculated.

Metal Oxide Semiconductor (MOS) Sensors

The sensitive source of metal oxide semiconductor gas sensor is mainly made of semiconductor material. The most widely used semiconductor material is not the common silicon and germanium semiconductor, but metal oxide semiconductor. The basic working principle of metal oxide semiconductor gas sensor: under certain conditions (temperature), after carbon dioxide (CO2) in the air contacts with metal oxide semiconductor material, the chemical composition will be changed through reduction or oxidation reaction, and the process will be accompanied by electric charge. The transfer further causes the change of the resistance of the semiconductor, and the detection of the gas can be realized by measuring the change of the resistance of the semiconductor.

CO2 gas detector

Portable CO2 detector, waterproof, dustproof, accurate detection data, sound and light alarm, long service life. The portable CO2 detector can be used in indoor air detection, gas leakage, pharmaceutical factories and other scenes.Portable CO2 detector, the body adopts ABS shell, it feels comfortable, light and portable.Portable CO2 detector, the body adopts ABS shell, it feels comfortable, light and portable.When the detected gas is more than the set gas value, the sensor will turn on the light alarm and the high-decibel buzzer will beep.The instrument is marked red to remind in time, and the safety is high.

Fixed gas detector

Fixed gas detector, stable performance, sensitive and reliable. With high-precision liquid crystal display, explosion-proof housing, diffusion type or pump suction type. The CO2 Gas Detector has the characteristics of flexible use and simple operation. The CO2 Gas Detector is used in various gas leakage places, such as: city gas, petroleum, chemical, pharmaceutical, steel, special industrial plants and other fields. The explosion-proof level of the CO2 Gas Detector is CT6.

Multi gas sensor module

Multi gas sensor module, strong anti-interference ability, high sensitivity, high resolution, small volume and it is easy to install, no secondary calibration, support secondary development support multi transmit method.The multi gas sensor module is widely used in the production and installation of portable and fixed gas detectors. And various gas detection occasions and equipment.

Applications of CO2 sensors

1. Application in aquaculture industry

Some large-scale farms, such as cattle, pig, chicken factories, etc., are in some closed or semi-closed environments. Because of their large numbers, these livestock exhale large amounts of carbon dioxide. If not ventilated in time, high concentrations of carbon dioxide will cause problems such as hypoxia, anorexia, and slow growth in animals. At the same time, lack of air movement can easily lead to weakened immunity and disease outbreaks in livestock.

Install carbon dioxide sensors on the farm to monitor the concentration of carbon dioxide. When the concentration of carbon dioxide in the farm reaches a certain amount, the exhaust system can be activated to replace fresh air and provide a good breeding environment for the growth of livestock.

2. Application of industrial waste gas

There are many types of industrial waste gas, which may cause different harm to the environment. Exhaust gas refers to the toxic and harmful gases emitted by human production and life. Especially chemical plants, steel plants, pharmaceutical plants, oil refineries, etc., as well as the production of domestic waste gas brought by human life. The smell of exhaust gas is very strong, which seriously pollutes the environment and affects human health.

As economies develop, human activities, such as burning fossil fuels and deforestation, contribute to increasing concentrations of greenhouse gases. There are also some industrial enterprises that generate a large amount of CO2 gas and discharge it from the opening of the pipeline. These make global warming one of the greatest challenges facing humanity today.

The greenhouse effect is quietly affecting people’s living environment, such as rising sea level, abnormal climate, increasing desertification area and so on. Therefore, it is necessary to monitor the concentration of flue gas when discharging industrial waste gas. A carbon dioxide sensor that measures the concentration of carbon dioxide can be installed in the chimney to strictly control the concentration of carbon dioxide in the exhaust gas.

3. Application of indoor HVAC

If there are many people in the room and the air is not ventilated, coupled with the CO2 emitted by the human body, the oxygen content in the air is relatively reduced, and the carbon dioxide concentration is increased, and the indoor people will have different degrees of poisoning symptoms.

Many people who often stay indoors like to turn on the air conditioner for ventilation, but the air purification effect of ordinary central air conditioners is poor, resulting in a lot of indoor air pollutants. Among them, gaseous pollutants are carcinogenic to the human body, and microorganisms are easy to cause various allergic diseases. Although the purification effect of the environmental protection air conditioner cannot be compared with that of the air purifier, but air passing through the environmental protection air conditioner is also odorless and fresh, so the indoor CO2 concentration will be reduced.

4. Application of agricultural greenhouse

All kinds of vegetables in agricultural greenhouses need to absorb carbon dioxide for photosynthesis. However, crops in greenhouses are kept in relatively closed places for a long time, and the carbon dioxide concentration inside them varies greatly within a day. Therefore, the shortage of carbon dioxide in the greenhouse is quite serious, which has become an important factor affecting the yield of greenhouse vegetables. The use of carbon dioxide sensors to control the concentration has also become an important factor affecting the crop yield. At present, many greenhouses have begun to use carbon dioxide sensor environmental monitoring equipment. The installation of carbon dioxide sensors in agricultural greenhouses can ensure timely alarm when the carbon dioxide concentration is insufficient, so as to use gas fertilizers. Ensure healthy growth of vegetables, flowers, etc.