What is two-wavelength infrared absorption technology for gas detectors?
Two-wavelength infrared absorption instruments are made according to the principle that hydrocarbon gases and vapours absorb infrared energy at certain wavelengths in the infrared region of the electromagnetic spectrum. The so-called two wavelengths, that is, the reference wavelength, hydrocarbons in this wavelength does not absorb infrared energy; measurement wavelength, hydrocarbons in this wavelength strongly absorb infrared energy. If there are hydrocarbons in the measurement area, the infrared energy measured on the measurement detector will be lower than that on the reference detector. The instrument gives the concentration of hydrocarbon gases and vapours by measuring the difference between the two.
It is based on FTIR technology - analytical - laboratory technology and is more suitable for occupational protection and work site monitoring. Compared to the catalytic combustion type, it has an extremely fast response time; it does not have the poisoning phenomenon of the catalytic combustion type; the accuracy is not affected by the speed of the hydrocarbon gas flow; the measuring range is as low as 0 to 1,000 ppm and as high as 0 to 100 per cent v/v; and it can be applied in inert gas environments because it does not require oxygen-air in the measurement.
It can be used in very harsh environments through the use of non-moving parts that are not affected by vibration and shock; the use of dust covers, splash shields and mirror heating technology; a non-depleting electronically circulating infrared light source with a lifetime of at least 4 years; no ageing of all components except the lamp; the measuring head has the property of automatically reporting faults through regular self-tests; calibration can be carried out every 6 months; therefore significantly reducing post maintenance costs and reducing the cost of maintenance compared to the FTIR technique. The calibration can be carried out every 6 months, thus significantly reducing maintenance costs and the possibility of false alarms compared to FTIR technology.
Due to the limitation of the infrared wavelength, it is only suitable for hydrocarbons with carbon-hydrogen bonds and cannot detect gases such as CS2, H2, CO, NH3, and hydrocarbons such as acetylene and benzene. Therefore it is more suitable for hydrocarbons with long chains than catalytic combustion sensors. Although the initial investment is expensive, the overall price is lower than catalytic combustion technology.
