萝莉影视

CO2 is a colorless and odorless gas at room temperature. The gas is emitted into the air by human and animal respiration and combustion of organic matter. It is consumed by plants through photosynthesis.

Global warming is believed to be caused by an increase in greenhouse gases. The impact of CO2, methane, nitrous oxide, chlorofluorocarbon gas, and other gases is large. It is said that CO2 has the greatest impact of those. Reducing CO2 emissions is a major challenge to suppress global warming and to maintain human society and the natural environment.

CO2 is used in dry ice and fire extinguishers. However, if the carbon dioxide (CO2) concentration in the air becomes high due to improper use, there is a risk of carbon dioxide poisoning.

The Ministry of Health, Labour and Welfare has released a warning to keep the indoor carbon dioxide (CO2) concentration at 1,000 ppm or less as the standard for good ventilation conditions. Frequent ventilation is required indoors where people gather together such as homes and offices. Appropriate ventilation and management using CO2 sensors is effective to manage the carbon dioxide (CO2) concentration. The use of NDIR system CO2 sensors is recommended from the perspective of measurement accuracy.

CO2 is consumed by plants through photosynthesis. That means the inside of a closed agricultural plastic greenhouse is prone to becoming an environment liable to suffer from a shortage of CO2. It is possible to expect increased yields and improved quality in crops by managing the carbon dioxide (CO2) concentration in plastic greenhouses and promoting the growth of crops by using CO2 gas generators and CO2 sensors.

CO2 sensors are devices that detect, quantify, and measure the carbon dioxide (CO2) concentration in the atmosphere. CO2 sensors are being introduced in various industries as a result of regulations and efforts to reduce greenhouse gas emissions in countries around the world. We introduce here some of the mechanisms and principles of CO2 sensors.

The non-dispersive infrared absorption method detects gases using the phenomenon in which the infrared rays at a specific wavelength are absorbed as a result of the molecular vibrations of the target gas caused by the emitted infrared rays. The infrared transmittance (the ratio of the transmitted light intensity to the emitted light intensity from the radiation source) is determined by the concentration of the target gas.

The photoacoustic effect is when a pulse of light from an infrared light source is passed through an optical filter adjusted to a wavelength that absorbs CO2 with the CO2 molecules in the measurement chamber, then absorbing the light that passes through the filter. The molecules shake with each pulse to generate pressure waves. Those pressure waves are then detected by a highly sensitive microphone to obtain a spectrum. The feature of photoacoustic spectroscopy is that it enables downsizing.

The thermal conductivity detector method measures the gas concentration by using the differences in thermal conductivity inherent to gases. A thermal sensor made using a heated platinum wire or similar detects the change in temperature due to the change in the thermal conductivity of the sample gas as a change in the electrical resistance to measure the concentration of the measurement component gas in the sample gas. It is common to use a bridge circuit that combines four thermal sensors to raise the sensing accuracy.

The easiest way to ascertain the accuracy of CO2 sensors is to check that the measured value is close to the about 415 ppm to 450 ppm when the CO2 concentration is measured outdoors. An even more accurate confirmation method is to place the CO2 sensor in a chamber filled with a known gas concentration and to then check whether the known value appears. In this case, it is effective to measure and compare the CO2 sensor being evaluated with an even higher accuracy CO2 sensor.

The reliability required varies depending on the used application. In the most severe agricultural applications, sensors are used for long periods of time at high temperature and high humidity. Sometimes, they are used in environments where condensation occurs.
They are also used in sulfur fumigation environments to prevent crop diseases and improve quality. This is a harsh environment for electronic devices.

The one light source, one optical path, one filter, and one element system requires atmospheric calibration. It is necessary to take the actual CO2 sensor out into the atmosphere or to draw in air close to the sensor with a tube for atmospheric calibration. The value will be correct immediately after calibration, but it may then gradually start to deviate. The system with a reference built into the device does not require calibration. Therefore, it can reduce the hassle and expense of maintenance involved in calibration.

CO2 sensors are used in a variety of applications. These applications include promoting photosynthesis in agriculture, controlling the air-conditioning in living spaces and buildings, managing the air quality inside automobiles, and detecting refrigerant leaks in refrigerators. The system is selected based on the requirements for each application such as the accuracy, reliability, environmental resistance, necessity of not requiring calibration, size, price, and output interface.
Some applications require a small size and a low price. However, there are also applications that require sensors that do not need to be calibrated, maintain their accuracy for a long time, and are resistant to breakdowns.