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An optical beam smoke detector is a device that uses a projected beam of light to detect smoke across large areas, [1] typically as an indicator of fire. [2] They are used to detect fires in buildings where standard point smoke detectors would either be uneconomical [ 3 ] or restricted for use by the height of the building.
Figure 2: [8] Working principle of a thermal laser sensor (Adapted from figure 3 with permission) As shown in Fig 2, a thermopile laser sensor consists of several thermocouples connected in series with one junction type (hot junction at temperature T 1) being exposed to an absorption area and the other junction type (cold junction at temperature T 2) being exposed to a heat sink.
Conceptual through-beam system to detect unauthorized access to a secure door. If the beam is interrupted, the detector triggers an alarm. A photoelectric sensor is a device used to determine the distance, absence, or presence of an object by using a light transmitter, often infrared, and a photoelectric receiver. They are largely used in ...
For smoke detectors according to EN 54-7 and fire detectors with smoke sensor (parts 12, 20 and 30 of EN 54) the test fires TF2, TF3, TF4 and TF5 are used. The EN 54-20 defines the following test fires with reduced fuel quantity for aspirating smoke detectors with enhanced or very high sensitivity (class A or B):
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 spectrometers) is used to separate out (like a monochromator) the broadband light into a narrow spectrum suitable for gas sensing.
This reduces the lateral spread of electrons from the electron beam within the detective layer of the sensor, allowing for smaller pixel sizes e.g. 6.5 x 6.5 μm for a Direct Electron DE-16. [12] Smaller pixel size allows for a large number of pixels to be incorporated into a sensor, although the dynamic range is typically more limited than for ...
An aspirating smoke detector (ASD) is a system used in active fire protection, consisting of a central detection unit which draws air through a network of pipes to detect smoke. [1] The sampling chamber is based on a nephelometer that detects the presence of smoke particles suspended in air by detecting the light scattered by them in the chamber.
As a rule of thumb, we want at least 10 pixels across the area that encompasses most, say 80%, of the energy in the beam. Therefore, there is no hard and fast rule to select the optimal beam size. As long as the CCD sensor captures over 90% of the beam energy and has at least 10 pixels across it, the beam width measurements will have some accuracy.