[ Huaqiang Security Network News ] Today , we can look at the composition and principle of the fire detector . This product can be divided into temperature detector, light detector, smoke detector and flammable gas detection in the security industry. The equipment, etc., the products of different applications are different. Let’s analyze what kind of fire detectors should be used in the following places! 
1, temperature detector
Temperature detectors can be divided into fixed temperature and differential temperature.
The constant temperature detector emits an alarm under the action of the temperature sensing element when the temperature at which the detector is installed rises to a predetermined temperature. The temperature sensing element has a low melting point alloy, a platinum wire, a bimetal, a bimetallic cylinder, a thermistor, and a semiconductor P-N junction.
A differential temperature temperature detector emits an alarm when the temperature rise within a timed period exceeds a certain limit. If the temperature rises above 10C or 15C within 1min, an alarm will be given. The sensitive components of the differential temperature detector mostly use bimetal differential temperature, bellows differential temperature and thermistor differential temperature component. When the temperature of the detection site rises sharply, the component action turn-on signal gives an alarm.
In order to improve the accuracy of automatic detection, both temperature sensing and differential temperature sensing elements can be used simultaneously in the temperature detector. It is suitable for fires to develop rapidly, generate a lot of heat, and the temperature rises very quickly, especially in places where there are a lot of dust, smoke and water vapor.
2, photosensitive detector
The photodetector can be divided into two types: infrared photodetector and ultraviolet photodetector. When the substance burns on fire, the flame temperature is generally above 1000 ° C, and is radiated around the light with various wavelengths, including ultraviolet radiation, visible radiation and infrared radiation. In order to detect these rays, an ultraviolet detector and an infrared detector were separately fabricated.
The sensitive components of the infrared detector are photoconductive batteries made of aluminum sulfide, barium sulfide, etc., germanium, silicon photo cells, germanium, silicon photodiodes and phototransistors. When this sensitive component encounters infrared radiation, it generates an electrical signal that amplifies it and alerts it.
The sensitive component of the UV photodetector is a UV-sensitive phototube that acts only on the UV light in the light. In the event of fire, the ultraviolet photosensitive tube is subjected to the action of ultraviolet rays of the flame, emits electrons, forms an avalanche discharge, turns on the electrical circuit, and sends an alarm signal.
Photosensitive detectors are especially suitable for inflammable and explosive places that suddenly catch fire without smoke. Not suitable for places with open fire operations, such as electric welding, fire welding and other places.
3, smoke detector
The smoke detector is divided into an ion smoke detector, a photo-electric smoke detector and a linear smoke detector. It can issue an alarm when there is no smoldering flame, and has the characteristics of early warning.
The ionized smoke detector consists of a detector and a signal electrical circuit. The detector consists of two silver (AL4') source sheets and a signal electrical circuit forming an inner ionization chamber and an outer ionization chamber. In the event of fire, the flue gas can change the equivalent impedance (increase) of the external ionization chamber, but the equivalent impedance of the internal ionization chamber does not change, thereby changing the voltage distribution of the internal and external ionization chambers and issuing an alarm signal.
The Photoelectric Smoke Detector is a simple smoke collector. The light collecting device is connected with the pipeline. When there is fire risk and smoke, the beam intensity decreases, the electrical loop current decreases, the relay acts, and an alarm signal is issued.
The linear smoke detector has two types: a laser smoke detector and an infrared smoke detector. Among them, infrared beam type smoke detectors are widely used. The laser and infrared light smoke detectors use the smoke to absorb and scatter the light beam, weaken the signal of the photoelectric receiver, and cause the receiver to send an alarm signal.
Smoke detectors are suitable for power stations, power distribution rooms, computer rooms, communication rooms, archives, libraries, important warehouses and other places.
4, combustible gas detector
Sensitive components of the combustible gas detector include a platinum wire element (coated with aluminum oxide and a catalyst thereon), a gas sensing semiconductor element, and the like. Gas-sensitive semiconductor components (commonly used tin oxide-type semiconductor gas sensors) have high sensitivity, and can detect combustible gas at a concentration of several ppm, and have a wide detection range. The working principle is: when there is a combustible gas, the resistance value of the gas-sensitive semiconductor component is changed, and the larger the concentration, the smaller the resistance value (N-type component), the output voltage is increased, thereby generating an electric signal, and an alarm is generated by amplification. .
The combustible gas detector can be made into a variety of portable and fixed structures to meet the needs of the field.
In the flammable and explosive places of power companies, chemical production workshops, oil stations, oil depots, hydrogen stations, hydrogen-cooled generator outlets, etc., where flammable gas is leaked outside, it is very convenient to use flammable gas detectors. Once a flammable gas leaks, a certain concentration is reached and an alarm signal is issued immediately.
Temperature detectors can be divided into fixed temperature and differential temperature.
The constant temperature detector emits an alarm under the action of the temperature sensing element when the temperature at which the detector is installed rises to a predetermined temperature. The temperature sensing element has a low melting point alloy, a platinum wire, a bimetal, a bimetallic cylinder, a thermistor, and a semiconductor P-N junction.
A differential temperature temperature detector emits an alarm when the temperature rise within a timed period exceeds a certain limit. If the temperature rises above 10C or 15C within 1min, an alarm will be given. The sensitive components of the differential temperature detector mostly use bimetal differential temperature, bellows differential temperature and thermistor differential temperature component. When the temperature of the detection site rises sharply, the component action turn-on signal gives an alarm.
In order to improve the accuracy of automatic detection, both temperature sensing and differential temperature sensing elements can be used simultaneously in the temperature detector. It is suitable for fires to develop rapidly, generate a lot of heat, and the temperature rises very quickly, especially in places where there are a lot of dust, smoke and water vapor.
2, photosensitive detector
The photodetector can be divided into two types: infrared photodetector and ultraviolet photodetector. When the substance burns on fire, the flame temperature is generally above 1000 ° C, and is radiated around the light with various wavelengths, including ultraviolet radiation, visible radiation and infrared radiation. In order to detect these rays, an ultraviolet detector and an infrared detector were separately fabricated.
The sensitive components of the infrared detector are photoconductive batteries made of aluminum sulfide, barium sulfide, etc., germanium, silicon photo cells, germanium, silicon photodiodes and phototransistors. When this sensitive component encounters infrared radiation, it generates an electrical signal that amplifies it and alerts it.
The sensitive component of the UV photodetector is a UV-sensitive phototube that acts only on the UV light in the light. In the event of fire, the ultraviolet photosensitive tube is subjected to the action of ultraviolet rays of the flame, emits electrons, forms an avalanche discharge, turns on the electrical circuit, and sends an alarm signal.
Photosensitive detectors are especially suitable for inflammable and explosive places that suddenly catch fire without smoke. Not suitable for places with open fire operations, such as electric welding, fire welding and other places.
3, smoke detector
The smoke detector is divided into an ion smoke detector, a photo-electric smoke detector and a linear smoke detector. It can issue an alarm when there is no smoldering flame, and has the characteristics of early warning.
The ionized smoke detector consists of a detector and a signal electrical circuit. The detector consists of two silver (AL4') source sheets and a signal electrical circuit forming an inner ionization chamber and an outer ionization chamber. In the event of fire, the flue gas can change the equivalent impedance (increase) of the external ionization chamber, but the equivalent impedance of the internal ionization chamber does not change, thereby changing the voltage distribution of the internal and external ionization chambers and issuing an alarm signal.
The Photoelectric Smoke Detector is a simple smoke collector. The light collecting device is connected with the pipeline. When there is fire risk and smoke, the beam intensity decreases, the electrical loop current decreases, the relay acts, and an alarm signal is issued.
The linear smoke detector has two types: a laser smoke detector and an infrared smoke detector. Among them, infrared beam type smoke detectors are widely used. The laser and infrared light smoke detectors use the smoke to absorb and scatter the light beam, weaken the signal of the photoelectric receiver, and cause the receiver to send an alarm signal.
Smoke detectors are suitable for power stations, power distribution rooms, computer rooms, communication rooms, archives, libraries, important warehouses and other places.
4, combustible gas detector
Sensitive components of the combustible gas detector include a platinum wire element (coated with aluminum oxide and a catalyst thereon), a gas sensing semiconductor element, and the like. Gas-sensitive semiconductor components (commonly used tin oxide-type semiconductor gas sensors) have high sensitivity, and can detect combustible gas at a concentration of several ppm, and have a wide detection range. The working principle is: when there is a combustible gas, the resistance value of the gas-sensitive semiconductor component is changed, and the larger the concentration, the smaller the resistance value (N-type component), the output voltage is increased, thereby generating an electric signal, and an alarm is generated by amplification. .
The combustible gas detector can be made into a variety of portable and fixed structures to meet the needs of the field.
In the flammable and explosive places of power companies, chemical production workshops, oil stations, oil depots, hydrogen stations, hydrogen-cooled generator outlets, etc., where flammable gas is leaked outside, it is very convenient to use flammable gas detectors. Once a flammable gas leaks, a certain concentration is reached and an alarm signal is issued immediately.
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