The pyroelectric infrared sensors from InfraTec, also called pyroelectric detectors, can detect the electromagnetic radiation (UV, VIS, IR, THz) that hits them and measure their intensity. When the radiation hits, the pyroelectric crystal heats up and positive electrical charges occur. Without radiation, the crystal cools down and negative charges are generated.
However, the charges are very small. Before they can balance out again through the final internal resistance of the crystal, extremely low-noise and low leakage current field-effect transistors (JFET) or operational amplifiers (OpAmp) convert the charges to a signal voltage.
Pyroelectric sensors are often used in gas analysis, flame detection as well as in spectroscopy and pyrometry.
Pyroelectric Detectors for Gas Sensor Technology
For gas sensor technology one can make use of the fact that the molecular vibrations of many chemical compounds have fundamental oscillations in the infrared wavelength range and therefore absorb IR radiation. Each of these compounds has a characteristic absorption spectrum.
An NDIR (Non Dispersive IR) gas analyser consists of an electrically or mechanically modulated IR source, a gas cell and usually a pyroelectric detector. An electronic evaluation unit uses the signal voltage to calculate the gas concentration. InfraTec offers a large number of standard IR narrow band filters (narrow band pass - NBP) which are optimally matched to the absorption properties of the gas to be measured. These filters are already integrated into the cap of the pyroelectric detector and facilitate the development of equipment for gas analysis.
Areas of Application for Gas Sensor Technology
Pyroelectric detectors have a very wide range of applications in gas sensors. Often they protect the environment or even human life! By measuring exhaust gases in industrial plants or measuring leaks on gas pipelines, countermeasures can quickly be taken in the event of malfunctions. Through the detection of toxic or flammable gases, it is possible to prevent poisoning or explosions in mining worldwide. Pyroelectric IR detectors are also indispensable in medicine. Thus, the function of the lungs can be analysed by measuring CO2. Or diseases can be identified in the breath by other measurements. The correct mixture of anaesthetic gases is also determined with detectors from InfraTec. And not least of all, breath alcohol measurements should ensure that only sober drivers are allowed to drive in traffic.
In addition, there are many other areas of application for InfraTec detectors. Thus, for example, in biogas analysis for determining the quality of coal, the health of plants and much more.
Pyroelectric Detectors for Flame Sensor Technology
In flame sensor technology pyroelectric detectors recognize radiation from burning gases, liquids or solids and can identify them using their characteristic IR spectrum. The typical spectral radiation of burning organic materials such as wood, natural gas, oil or plastic is recorded. Two independent criteria of a flame are evaluated in order to rule out a false alarm from the sun or other intense light sources (e.g. sun or welding arc):
- An open flame (in contrast to solar radiation) is characterized by a flicker frequency between 1 and 5 Hz.
- In addition to the combustion gas of hydrogen H2O, a hydrocarbon flame also produces that of carbon CO and CO2. Their emission bands are in the infrared spectral range between a 4.0 and 4.8 µm wavelength. In order to obtain a high signal, wide IR bandpasses are used as detector windows, which include both the radiation emission of CO2 and CO.
Fields of Application in Flame Sensor Technology
Everyone knows the inexpensive smoke alarms that hang in many private apartments. These prove very useful for small rooms, in which it is better to warn once time too much. If, however, flames are detected over long distances, or outside rooms or large halls have to be monitored, then pyroelectric IR detectors are used. Flame detectors with pyroelectric detectors evaluate the radiation bands of the burning substances and the flicker frequency of the flame. By analysing two independent characteristics of a flame simultaneously, false alarms can largely be avoided.
These are used, among other things, on oil rigs, in warehouses or production halls, in aircraft hangars or in refineries.
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.