Gas detector classification Gas detector principle
Classification of gas detectors
According to volume, it can be divided into desktop gas detector and handheld gas detector
According to the number of gases that can be detected, it can be divided into single gas detector and multiple gas detector
According to the principle of gas sensor, it can be divided into infrared gas detector, thermomagnetic gas detector, electrochemical gas detector, semiconductor gas detector, ultraviolet gas detector and so on.
The principle of gas detector
Take the common infrared gas detector as an example to illustrate the principle of the gas detector:
Measuring this absorption spectrum can identify the type of gas; measuring the absorption intensity can determine the concentration of the gas being measured. The infrared detector has a wide range of applications. It can not only analyze gas components, but also analyze solution components. It has high sensitivity, rapid response, continuous online indication, and can also form an adjustment system. The detection part of the infrared gas detector commonly used in industry is composed of two parallel optical systems with the same structure.
One is the measurement room and the other is the reference room. The two chambers open and close the light paths simultaneously or alternately at a certain period through the light cutting plate. After the gas to be measured is introduced into the measurement chamber, the light with the specific wavelength of the gas to be measured is absorbed, thereby reducing the luminous flux that passes through the optical path of the measurement chamber and enters the infrared receiving gas chamber. The higher the gas concentration, the less the luminous flux entering the infrared receiving gas chamber; while the luminous flux passing through the reference chamber is constant, the luminous flux entering the infrared receiving gas chamber is also constant. Therefore, the higher the measured gas concentration, the greater the difference in luminous flux that passes through the measurement chamber and the reference chamber. This luminous flux difference is projected to the infrared receiving air chamber with a certain periodic vibration amplitude. The receiving gas chamber is divided into two halves by a metal film with a thickness of several microns. The gas of the measured component with a relatively high concentration is sealed in the chamber, which can absorb all the incoming infrared rays in the absorption wavelength range, so that the pulsating luminous flux becomes The periodic change of temperature can be converted into a change of pressure according to the gaseous state equation, and then detected by a capacitive sensor, which indicates the concentration of the gas to be measured 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 adjustable lasers are used as light sources to form a new all-solid-state infrared gas detector. This detector can complete the measurement of gas concentration with only one light source, one measurement chamber and one infrared sensor. In addition, if a filter disc equipped with multiple different wavelengths is used, the concentration of each gas in the multi-component gas can be measured separately at the same time.
The use of gas detector
The gas detector can detect hydrogen sulfide, carbon monoxide, oxygen, sulfur dioxide, phosphine, ammonia, nitrogen dioxide, hydrogen cyanide, chlorine, chlorine dioxide, ozone and combustible gases and other gases, widely used in petrochemical, coal On-site detection in various places such as metallurgy, chemical industry, municipal gas, and environmental monitoring. It can meet the measurement needs of special occasions; it can detect gas concentration or leak detection in tunnels, pipelines, tanks, and confined spaces.
Maintenance of gas detector
1. Check the gas flow rate, usually 30/h, if the flow rate is too large or too small, the result will be greatly affected
2. Replace the filter paper: stop the air pump and drain the filter tank
3. Check whether there is any air leakage in the air system. Whether the diaphragm of the weeping pump is damaged, whether the sampling sealing ring is broken, whether the four-way valve and condensate are damaged, etc.
4. Clean the sampling probe and dredge the sampling hole pipeline
5. Check whether the condenser works normally, usually the temperature is adjusted within 3 degrees Celsius
6. Check the measuring chamber to see if it is dirty, and clean it in time.
