“The flame detector detects that when a substance burns, it produces smoke and emits heat, and it also produces visible or invisible light radiation that is not in the atmosphere. Flame burning radiation light wave band flame detector is also called photosensitive fire detector. It is a kind of fire detector used to respond to the light characteristics of fire, that is, to detect the light intensity of flame burning and the flicker frequency of flame.
The flame detector detects that when a substance burns, it produces smoke and emits heat, and it also produces visible or invisible light radiation that is not in the atmosphere. Flame burning radiation light wave band flame detector is also called photosensitive fire detector. It is a kind of fire detector used to respond to the light characteristics of fire, that is, to detect the light intensity of flame burning and the flicker frequency of flame.
According to the light characteristics of the flame, there are three types of flame detectors currently in use: one is the ultraviolet detector that is sensitive to the ultraviolet radiation with a shorter wavelength in the flame; the other is the ultraviolet detector that is sensitive to the infrared radiation with a longer wavelength in the flame Infrared detectors; the third type is an ultraviolet/infrared hybrid detector that detects both the short-wavelength ultraviolet rays and the longer-wavelength infrared rays in the flame.
According to the detection band, it can be divided into: single ultraviolet, single infrared, dual infrared, triple infrared, infrared ultraviolet, additional video and other flame detectors.
According to the explosion-proof type, it can be divided into: explosion-proof type and intrinsically safe type.
For ultraviolet rays with a wavelength of 0.185~0.260μm generated in flame combustion, a solid substance can be used as a sensitive element, such as silicon carbide or aluminum nitrate, or an inflatable tube can be used as a sensitive element, such as a Geiger-Mille tube.
For the infrared rays with a wavelength of 2.5~3μm generated in the flame, a sensor made of aluminum sulfide materials can be used, and for the infrared rays with a wavelength of 4.4~4.6μm generated by a flame, a sensor made of lead selenide material or aluminum tantalate material can be used. Different sensors can be selected according to the emission spectrum of different fuel combustion, and the triple infrared (IR3) is widely used.
The flame burning process releases ultraviolet, visible, and infrared, which have typical characteristics at a specific wavelength and specific flicker frequency (0.5HZ-20HZ), which is different from other interference radiation. The ultraviolet and infrared radiated by sunlight, hot objects, electric lamps, etc. have no flicker characteristics .
The working principle of the flame detector is to detect the flame by detecting the special wavelength of ultraviolet, infrared and visible light radiated by the flame, and at the same time with the identification of the characteristic flicker frequency of the flame. Generally, ultraviolet photodiodes, ultraviolet detectors, ultraviolet sensors, etc. are used as detection elements.
The ultraviolet detector is a sensor that converts one form of electromagnetic radiation signal into another form that is easy to be received and processed. The photodetector uses the photoelectric effect to convert optical radiation into electrical signals. The photoelectric effect can be divided into external photoelectric effect and internal photoelectric effect.
The external photoelectric effect device usually refers to a photosensitive electric vacuum device, which is mainly used in the ultraviolet, infrared and near-infrared wavebands. External photoelectric effect devices with internal gain include photomultiplier tubes, image intensifiers and other photosensitive electric vacuum devices. They have extremely high sensitivity, can convert extremely weak light signals into electrical signals, and can perform single photon detection. semiconductor devices with electro-optical effects are several orders of magnitude higher.
The internal photoelectric effect is divided into the light guide effect and the photovoltaic effect. In the photoconductivity effect, after a semiconductor absorbs enough energy photons, it activates some of the electrons or holes from the original non-conductive bound state to a conductive free state, which leads to an increase in the conductivity of the semiconductor and a decrease in the resistance in the circuit. In the photovoltaic effect, the photo-generated charge produces a small PN potential difference across the junction in the semiconductor. The generated photovoltage is amplified by optoelectronic devices and can be directly measured. The devices made according to the photoconductive effect and the photovoltaic effect are called semiconductor photoconductive detectors and photovoltaic detectors, respectively.
Finally, four high-quality UV detectors imported from abroad by Gongcai.com are recommended. The first is the flame detector-RFD-3000 and the flame detector-RFD-3000X. RFD-3000 and RFD-3000X are a multi-spectral infrared (infrared) ), suitable for general site, indoor and outdoor site applications. With a wide field of view of 90 degrees and an effective performance range of 60 meters, the fire can be quickly detected. Output includes relay, 4 to 20 mA output, RS-485 communication mode.
Finally, the flame detector-RFD-2000X and flame detector-RFD-2000X-H, RFD-2000X and RFD-2000X-H is a UV infrared flame detector, suitable for dangerous and safe scenes, indoor and outdoor scenes application. With a wide field of view of 90 degrees and an effective performance range of 30 meters, the fire can be quickly detected. Self-diagnosis test function, waterproof and explosion-proof structure, can be used safely in industrial places such as oil refineries and gas facilities. Output includes relay, 4 to 20 mA output, RS-485 communication mode.