Pyroelectric Detectors in Gas Analysis
A large number of gases absorb infrared radiation by intramolecular vibrations. For each specific material, the absorption intensity depends on the wavelength of the infrared radiation. This principle uses a non-dispersive infrared gas analyzer (NDIR gas analyzer) for gas analysis. The analyzer consists of an electronically or mechanically modulated infrared source, a sample cell through which the gas flows to be measured, and a pyroelectric detector.
In the detector cap, a narrow band pass filter (NBP Filter) is integrated, whose pass band corresponds to the absorption wavelength of the target gas. With the thermal detector, the transmission of the measured gas mixture is determined in a defined arrangement. If the gas being searched for is not present, most of the infrared radiation will reach the detector and the signal will be at its maximum. If the concentration of the gas increases, absorption will also increase according to Lambert-Beer's law, and the signal will reduce accordingly.
This concept finds itself again in standard InfraTec infrared filters with a center wavelength (CWL) of 4.27 µm and a half power bandwidth (HPBW) of 170 nm are suitable for the measurement of carbon dioxide (CO2), for example.
Multi-channel Measurement
NDIR gas analysis cannot resolve complex forms of absorption bandwidths. Instead it uses an averaged signal measurement within the filter pass band. With this, you now have a manageable, long-time stable and continuously operating measurement method for industrial gas analysis at your disposal. Gas identification and transverse sensitivity of gas mixtures often require spectral multi-channel evaluations.
The classic gas analysis setup with filter wheel and/or mechanical chopper requires relatively fast (> 200 Hz) pyroelectric detectors with strong output signals. For this purpose, we offer multiple types with integrated JFET or CMOS operational amplifiers and pyroelectric elements, which are wired up for current mode operation.
Pyroelectric Detectors for Gas Analysis
LME-335/LME-336
a measuring channel, high power, temperature compensation, reduced acceleration response, single or split power supply
LIM-262/LIM-272
a measurement and a reference channel, temperature compensation, single or split power supply
Case Studies about Pyroelectric Detectors in Gas Analysis
Detection of Gas Leaks
A pyroelectric sensor generates a signal as soon as it is illuminated with an electrically or mechanically modulated infrared source. By integrating a gas-specific narrow band pass filter, which is tuned to a specific gas, the pass band is spectrally limited. The installation of a CO2 standard filter with a CWL of 4.27 µm and a HPBW of 170 nm means that only radiation in this wavelength range will impact with the pyroelectric chip. If a gas begins to leak - in this case, CO2 - less radiation hits the detector and the signal gets weaker. The use of a second so-called reference channel with e.g. a CWL of 3.95 µm and a HPBW of 90 nm enables a more accurate detection of gas leaks that is less prone to error.
Alcohol Test
Instruments for breath alcohol control for motorists are also among the application areas of gas detectors. The very precise measurements serve the police as evidence of alcohol or drug abuse behind the wheel.
Plant Health
With pyroelectric detectors, even the photosynthetic metabolic processes of plants can be monitored. Especially the measurement of CO2 is of interest here.
Technical Article: Low Cost Optical Electronic Nose for Biomedical Applications
Article about the development of an optical-electronic nose with a non-dispersive infrared sensor (NDIR), which is to be aimed at healthcare applications.
Oil Production
A number of companies use infrared detectors for both high-temperature drilling operations as well as for work that lasts for days. Here, the gas concentrations can be measured and thus the rate of penetration controlled.
Detection of Disease
Certain diseases cause specific patterns of exhaled air. For the past few years, NDIR gas analysis has provided an additional opportunity for diagnosis, for example of cancer or gastric diseases. In these cases, bacteria such as Helicobacter pylori can be detected by a non-invasive method. A special substance will be taken by the patient. At presence of helicobacter pylori bacteria it generates C13 carbon atoms. Those can be measured by the NDIR method simply analyzing the exhalation air.
Water and Steel Analysis
Infrared detectors are used in devices that identify impurities in materials having different physical states. With liquids like water, a sample is cooked and the gases released are measured. A similar test method is used in the manufacturing of steel. This is to ensure the proper composition of the steel alloy. Here, steel pellet samples are heated and the concentration of the gases produced is analyzed.
Detector Search
InfraTec offers five different product groups including approximately 50 standard pyroelectric detectors. Choose your suitable infrared detectors with the help of our detailed detector search.
