{{unreferenced, date=May 2016 An infrared point sensor is a point

gas detector A gas detector is a device that detects the presence of gases in an area, often as part of a safety system. A gas detector can sound an alarm to operators in the area where the leak is occurring, giving them the opportunity to leave. This type of d ...

based on the

nondispersive infrared sensor A nondispersive infrared sensor (or NDIR sensor) is a simple spectroscopic sensor often used as a gas detector. It is non-dispersive in the fact that no dispersive element (e.g a prism or diffraction grating as is often present in other spectrome ...

technology.

Principle

Dual source and dual receivers are used for self compensation of changes in alignment, light source intensity and component efficiency. The transmitted beams from two

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

sources are superimposed onto an internal

beam splitter A beam splitter or ''beamsplitter'' is an optical device that splits a beam of light into a transmitted and a reflected beam. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding wide ...

. 50% of the overlapping sample and reference signal is passed through the gas measuring path and reflected back onto the measuring detector. The presence of combustible

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

will reduce the intensity of the sample beam and not the

reference beam A reference beam is a laser beam used to read and write holograms. It is one of two laser beams used to create a hologram. In order to read a hologram out, some aspects of the reference beam (namely its angle of incidence, beam profile and wavel ...

, with the difference between these two signals being proportional to the concentration of gas present in the measuring path. The other 50% of the overlapped signal passes through the beam splitter and onto the compensation detector. The compensation detector monitors the intensity of the two infrared sources and automatically compensates for any long term drift.

Mean time between failures Mean time between failures (MTBF) is the predicted elapsed time between inherent failures of a mechanical or electronic system during normal system operation. MTBF can be calculated as the arithmetic mean (average) time between failures of a system ...

may go up to 15 years.

Micro heaters

Micro

heaters A heater is an appliance whose purpose is to generate heat for a building. Heater or Heaters may also refer to: Science, technology and engineering * Central heating, a system used to heat an entire building Devices * Aquarium heater, in fishkee ...

can be used to raise the temperature from optical surfaces above ambient to enhance performance and to prevent condensation on the optical surfaces.

Range

Toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...

gases are measured in the low parts per million ( ppm) range. Flammable gases are measured in the 0 - 100%

lower flammable limit Lower flammability limit (LFL), usually expressed in volume per cent, is the lower end of the concentration range over which a flammable mixture of gas or vapour in air can be ignited at a given temperature and pressure. The flammability range is de ...

(LFL) or

lower explosive limit Mixtures of dispersed combustible materials (such as gaseous or vaporised fuels, and some dusts) and oxygen in the air will burn only if the fuel concentration lies within well-defined lower and upper bounds determined experimentally, referred to a ...

(LEL) range.

Principle

Micro heaters

Range

See also