What principle does the smoke sensor work on?

Smoke sensor is a kind of sensor that uses the physical change of gas to detect the fire hazard source, the smoke concentration and temperature in the accident site. This sensor measures changes in the composition and quantity of various substances in the air by detecting gas flows, and transforms this signal into an electrical signal. Therefore, smoke sensors are also known as smoke detectors.

There are three main types of common smoke sensors, namely, infrared, ultrasonic and electronic. They must be installed with fixed screws to prevent screw loosening and causing fire accidents. These devices and principles are basically the same, but they will vary according to the installation location. Here's a detailed look at some of these common smoke sensors.

1. Infrared type

 Infrared smoke sensors detect fire hazards by transmitting and receiving infrared light. After a fire, the flame will spread from the test area. The infrared light absorbed by the fire source is amplified into an electrical signal that outputs a signal to the brain. The sensor will determine the alarm signal and the processing level (the waveform), and convert the signal into a digital signal and transmit it to the computer. It also uses digital processing technology to respond to the smoke.

Infrared smoke detector, which is a beam of light wave through an object exposed to the object, and then will be absorbed into the internal for analysis and processing, in the process of emitting the microwave wavelength of short infrared light (red) band of infrared. After detection, output the corresponding signal voltage. When a fire occurs, the short circuit inside the sensor occurs due to the electrochemical reaction, resulting in the induction voltage rise and signal distortion (or signal instability), so that the alarm can not be issued. Therefore, when the infrared smoke sensor is installed in the air, it will convert the flue gas into an electrical signal and be transmitted to other directions for detection.

2. Ultrasound type

 There are three main sensors of ultrasonic smoke sensor, which are infrared type and internal components. Infrared smoke sensor is mounted on the ceiling or wall, which has the advantages of simple installation, easy maintenance and low maintenance costs. But because of the attenuation of sound waves and penetration depth, it cannot be installed outside the fire sensor. The ultrasonic smoke sensor is that it measures the concentration and temperature of the measured gas through a series of sensors, such as aerosols. For example, the ultrasonic (Measure-Infrastructure) principle is used to detecting carbon monoxide.

 Ultrasonic sensor is similar to infrared smoke sensor, so it also has the advantages of small size, light weight and simple operation. But because of its low transmission power and improper use, it is easy to make the equipment leakage, and there are certain safety risks for the surrounding personnel. And the ultrasonic smoke sensor relies on the speed of gas molecules to measure the smoke concentration.

 During detection, if the gas is large, it will be quickly heated up or cooled to form fog. This phenomenon will directly affect the diffusion of smoke gas and reach the test area, and eventually produce a flame or high temperature gas. So that the test object is in danger or fire accident resulting in the expansion of losses (or casualties) and other consequences. Therefore, due to the influence of sound waves and the change of environmental factors, it is easy to lead to smoke, leakage and fire, so it is necessary to conduct monitoring analysis in advance to judge the fire and personnel escape mode in advance, to minimize the loss.

Generally, acoustic and optical alarms, ultrasonic sensors, infrared smoke sensors and other devices can be used to monitor fire high risk areas. The use of ultrasonic smoke sensor in the alarm device can not only improve the identification ability of the equipment, but also reduce the damage and loss caused to the equipment when entering the fire site. And also has a higher cost performance advantage, so there is this product on the market!

3. electronic formula

 Electronic smoke sensor is generally designed based on the circuit board, its working principle is roughly: when the current output in the circuit exceeds a certain threshold, it represents the circuit failure; when the current drops to a certain value, it means that the circuit failure and automatically cut off the power supply. This fault is generally due to the high content of gas in the smoke. It can be used to measure the gas concentration when the sensor is at a low conductivity.

This is also applicable to some places with high gas concentrations, because they use sensors to detect gas concentrations to better react to ignition sources. The alarm immediately occurs when the electronic smoke detector detects a high gas concentration; the smoke automatically goes out or alarms when the temperature reaches the set point. It is usually used in indoor areas, areas with low combustible gas concentration and more people.