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

Single channel detectors

LIM-262/LIM-272

a measurement and a reference channel, temperature compensation, single or split power supply

Multi channel detectors

Anesthesia Monitoring - Picture Credits: © Beerkoff / Fotolia.com

Medical Gas Analysis

A person's breath resembles a gaseous profile of their state of health. Thus, for example, diabetes, cancer, or stomach diseases can be reliably diagnosed by means of non-invasive breath gas measurement systems – without taking blood samples. NDIR gas analysis is also used in lung function diagnostics to determine the performance of the lungs, for example in competitive athletes. Gas detection also plays a role in hospitals. There, detectors are found in measuring devices that control the anaesthesia and composition of the anaesthetic gas mixture in the operating rooms.

Infrared Flame Sensor / Infrared Flame Monitoring - Picture Credits: © ttstudio / Fotolia.com

Industrial Gas Analysis

Infrared detectors are fundamental for industry. They detect explosive or environmentally harmful gases in the event of gas leaks and are used to measure industrial exhaust gases in order to comply with emission limits. Elemental analysis is another field of application. In this context, the detectors are used to identify impurities in substances with different states of aggregation or in steel production to guarantee the correct composition of the steel alloy. In high-temperature drilling processes, infrared detectors measure the gas concentration and provide information about the drilling progress.

Safety Technology

Blast explosions are a major risk in mining. A mixture of methane and air can ignite in the process. To ensure the safety of miners, the timely detection of methane is crucial. Infrared detectors detect even the smallest concentrations. Due to their small size, detectors are also used in portable safety devices such as mobile gas detectors. Their areas of application include the monitoring of workplaces and leak detection.

Environmental Protection

Pyroelectric detectors can be used to monitor metabolic processes of plants caused by photosynthesis. The measurement of CO2 is of particular interest here in order to research the absorption capacity of plants. Infrared sensor technology also plays a role in vehicle exhaust gas analysis. NDIR gas analysis is used to comply with applicable exhaust emission standards and to determine pollutant classes. It measures the concentration of emitted pollutants.

Furthermore, the detectors can be used to monitor coolants in industry, retail, or vehicles. As a component of leak detectors, they identify leaks where the environmentally hazardous coolant is leaking out. In this way, measures can be initiated in good time to secure the leak.

Process Gases

The monitoring of process gases is essential for the precise management of a process, but also indispensable for the safety of employees. Many process gases are flammable, highly explosive, and belong to the greenhouse gases. Also with a view to economic efficiency, process gases should be consumed in as small a quantity as possible. Particularly in the highly technical production of semiconductors, gases and waste gases are produced in many production processes. For this reason, permanent monitoring is essential. In the chemical or food industry, monitoring the room air also plays a decisive role. For safety reasons, the gases present must be monitored immediately and reliably.

Breath Alcohol Testing

Measuring devices for checking the breath alcohol level of drivers are also among the areas of application of gas detection detectors. They detect even the lowest breath alcohol concentrations and enable very accurate readings that serve the police as evidence of alcohol or drug abuse behind the wheel. One fifth of work-related accidents are also attributable to alcohol. It is not a new finding that the number of alcohol-related road accidents is a major problem. For this reason, bus drivers and train drivers must undergo an alcohol test before starting work.

Liquid Analysis

Pyroelectric detectors are used to ensure constant product quality and to check compliance with standards and limit values in liquids such as soft drinks or milk. During the production process, they check the composition and concentration of the individual components - without taking samples. This provides information about the sugar or lactose content, for example. But they also allow the identification of substances that are harmful to health.

Radiation Measurement

Laser treatments – whether in dermatology or ophthalmology – require the highest safety standards. For this reason, infrared detectors are used in laser systems. They measure the energy emitted by the laser beam and check the correct power output during patient treatment. If the detector notices that the intensity of the laser is too high, it switches off immediately. Fluctuations in the energy supply can be regulated due to the measurements.

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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.

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