According to the type of smoke alarm sensor is divided into both ionization sensor and photoelectric smoke detector.
How does ionization sensor work?
There is a very small amount of alpha radioactive material (Am241) in the sensor of the ionization type smoke alarm between the two charged plates. The air causes ionization under the impact of alpha particles, producing a large number of positively charged ions and electrons. After a certain voltage applies to both ends of the chamber. The positive and negative ions in the air move to the opposite electrodes to form a current. Once smoke enters the ionization chamber and interferes with the normal movement of the charged particles. The current will change and the detection circuit will detect this. The changed electrical signal is simple. When the amount of change reaches the alarm point, the alarm will enter the alarm state.
How does photoelectric smoke sensor sensor work?
Photoelectric smoke alarm is composed of infrared light-emitting tube, infrared induction tube and a dark room. In the absence of smoke, the light from the infrared light-emitting tube cannot reach the infrared light-sensing tube. When smoke enters the small dark room, these small smoke particles scatter the light emitted by the infrared light-emitting tube, causing part of the light to be received by the infrared-sensing tube. , and converted into an electrical signal, the detection circuit amplifies this electrical signal, when the alarm point is reached, the alarm enters the alarm state.
The pre-fire combustion has 2 types: smoldering type smoldering fires do not produce flames. They produce smoke particles with relatively large volume (3 to 5 microns). And smoldering fires produce smoke flow and It spreads out slowly. Because these types of fires burn very slowly and the smoke spreads very slowly. The smoke particles have enough time to stick to each other and combine, just as the smoke particles grow. This will make the smoke particles larger. Larger smoke particles have strong diffusion of light, and the use of photoelectric detection technology can have a good effect on the detection of such fires.
Types of Open Flames Flame (open flame) types of fires all have flames and produce large quantities of extremely small smoke particles (which may contain negatively charged ions). These particles are very small, (0.5-3 microns). Tnd these particles are invisible to the human eye. For example, the smoke produced when natural gas burns is this kind of smoke. The detection of open flames (fast burning fires) is better with ionic smoke alarms.