How the gas detection part of an air quality monitor works

Why Air Testing? The reason is that indoor environmental pollution has become one of the killers that seriously affects human health.

The importance of indoor air quality We spend more than 70% of our time in the indoor environment. Good indoor air quality is the most important factor to ensure good health, substandard indoor air can lead to physical discomfort and poor health (such as headache, chest tightness, drowsiness, allergies, eye strain, frequent colds, etc.). Pregnant women, children, the elderly, office workers, and people with respiratory and cardiovascular diseases are more susceptible to poor indoor air quality.

Common Indoor Air Pollutants 1Contamination of building materials. The gypsum board used in modern building decoration breeds bacteria, viruses and other microorganisms; 2.

Pollution caused by enclosed buildings. The fully enclosed building isolates the flow of natural fresh air....

This instrument adopts the principle of high-sensitivity electrochemical sensor, combined with single-chip microcomputer technology and network communication technology, which can continuously monitor SO2, NO2, O3, CO, H2S, NH3 and HF gases in the atmosphere, and comprehensively display the required measurement data. First of all, the ambient air is sent to the sensor air chamber by the air pump through the filter, and then sent to the sensor gas chamber with a flow rate of 300ml min respectively after passing through the sensor, and the signal generated when passing through the sensor is amplified and converted by a d, and the microprocessor collects, calculates, and processes the data to generate the concentration result data, and saves the data results or sends them to the information center through the RS485 serial interface.

For the detection of trace gases in the air, cross-interference between different gases is particularly prominent, and if it is not handled well, it will have a great impact on the test results. We solved this problem with two key technologies: first, the use of dedicated sensors for ambient air quality; The second is to use selective and appropriate filters, so that the monitoring results of the system are accurate and reliable.

Dismantling detector, detector principle, how laser detector is detected.

1. Metal oxide semiconductor sensor.

The metal oxide semiconductor sensor uses the adsorption induction of the measured gas to transform the conductivity of the semiconductor, and through the comparison of the process current change, the alarm circuit is excited. Because the semiconductor sensor is Chinese New Year's Eve more affected by the situation when measuring, the output line shape is not stable. Metal-oxide semiconductor sensors, because of their very sensitive responses, are now commonly used to measure the micro-leakage of gases.

2. Catalytic incineration sensor.

Catalytic incineration sensor is one of the most commonly used methods for detecting combustible gases, which has the characteristics of good output signal shape, reliable index, low price, and no interspersed annoyance with other non-combustible gases.

The catalytic incineration sensor adopts the principle of Wheatstone bridge, and the resistance and the combustible gas in the situation produce flameless incineration, so that the temperature changes the resistance value of the sensory resistance, breaks the bridge balance, and makes it output a stable current signal, and then through the reduction and stability of the early circuit, the final performance of the value is solid.

Because there are many types of gases and their physical and chemical properties are also different, there are many detection methods used, such as thermal conductivity, infrared, catalytic combustion, and so on.

Take the common infrared gas detector as an example to explain the principle of the gas detector:

Measuring this absorption spectrum allows for the identification of the type of gas; Measuring the absorption intensity determines the concentration of the gas being measured. The infrared detector has a wide range of use, which can not only analyze the gas composition, but also the solution composition, and has high sensitivity, rapid response, continuous indication, and can also form a regulating system. The detection part of the infrared gas detector commonly used in industry consists of two optical systems with the same structure in parallel.

One is the measuring room and the other is the reference room. The two chambers open and close the optical path simultaneously or alternately at a certain period through the cutting plate. When the measured gas is introduced into the measurement chamber, the light with the specific wavelength of the measured gas is absorbed, resulting in a decrease in the luminous flux that enters the infrared receiving chamber through the light path of the measuring chamber.

The higher the gas concentration, the less luminous flux enters the infrared receiving chamber; The luminous flux through the reference chamber is certain, and the luminous flux entering the infrared receiving chamber is also certain. Therefore, the higher the concentration of the gas to be measured, the greater the difference in luminous flux through the measuring chamber and the reference chamber. This luminous flux difference is projected onto the infrared receiving chamber at the amplitude of a certain period of vibration.

The receiving gas chamber is divided into two halves by a metal film several microns thick, and the chamber is sealed with a large concentration of the measured component gas, which can absorb all the incoming infrared rays in the absorption wavelength range, so that the pulsating luminous flux becomes a periodic change of temperature, and then the change of temperature can be converted into a change of pressure according to the gaseous equation, and then detected by a capacitive sensor, and the measured gas concentration is indicated after amplification. In addition to capacitive sensors, quantum infrared sensors that directly detect infrared rays can also be used, and infrared interference filters are used for wavelength selection and tunable lasers as light sources to form a brand-new all-solid-state infrared gas detector. This detector uses only one light source, one measuring chamber and one infrared sensor to measure the gas concentration.

In addition, if multiple filter discs with different wavelengths are used, the concentration of various gases in a multi-component gas can be measured separately at the same time.

1. The air quality sensor is used for the monitoring of particulate matter.

Particulate matter front imitation sensor.

The comprehensive application of domestic air purifiers began with the outbreak of haze, and sensors were first recognized by the public. Early sensors were simply an infrared gas detector with a level output that showed the air conditions with red, yellow and green indicators. The national standard stipulates that when the concentration in the air is less than 35 g m3, it is excellent and is shown in green.

However, some manufacturers cheat by changing the definition value, for example, when the concentration is less than 100 g m3, the display is green, and the consumer sees the indicator light change from red to yellow and then to green, thinking that the concentration of particulate matter in the air has been reduced to a safe range, fooling the consumer.

With the upgrading of domestic sensor technology, the analog qualitative output of the sensor is turned into quantitative output, and the concentration is directly displayed, realizing the digitization of air quality, enterprises have no chance to cheat, and consumers can also understand the air quality status more intuitively, which further promotes the healthy development of the purifier industry.

Application development of particulate matter sensors.

As we all know, the smaller the particle size, the more harmful the attached germs will be to the human body. It can enter blood vessels, and harmful substances attached to it can cause cancer;Although PM10 does not directly enter our alveoli, it can cause damage to our throat and airwaysAnd the damage is even greater.

At present, many European and American countries are paying more attention to PM10 pollution, and South Korea has incorporated monitoring into national standards. At present, the consumption upgrade is also being carried out in China, and the monitoring of more than 10 high parameters of the strong denier is promoted to promote the in-depth development of the purifier industry. This places higher demands on air purifiers, starting with filters, which must not only be able to remove, but also have the ability to handle smaller particlesSecondly, the sensor should not only measure multiple channels, but also achieve low noise, long life, and high reliability.

The air quality sensor can be used to detect various pollutants in the atmosphere, such as particulate matter, sulfur dioxide, ammonia, formaldehyde and other harmful gases. One of the most common sensors is the sensor, which is used to detect particles in the air with a diameter of less than or equal to microns, because these small particles can cause a variety of diseases such as respiratory and cardiovascular systems when they enter the human body.

The Loefmai sensor is an air quality sensor with high sensitivity, good stability and low power consumption. It uses the principle of laser scattering, which can monitor indoor and outdoor concentrations in real time, and connects to smartphones or cloud platforms via WiFi or Bluetooth, which is convenient for users to know the air quality status in real time. Loefmeer sensors not only have a fashionable appearance, easy to carry and install, but also have the advantages of high precision, high stability, and long service life.

In short, the Loefmai sensor is a very practical air quality detection device, which can be used in different scenarios such as home, office, and car to help people and liquid stools to grasp the surrounding situation and protect their health.

It is mainly to monitor the temperature and humidity in the atmospheric environment and 10 atmospheric pressure, ozone, nitrogen dioxide, carbon dioxide, carbon monoxide, etc.