At 7:46 in the morning, the G63 high-speed train from Jinan to Wenzhou was running smoothly in the track, but it was not long before passengers noticed that the train was slowing down. ¡°The speed is reduced from more than 200 kilometers to more than 100 kilometers. "Mr. Chen, who is in the car, said this. Later, after investigation, it was originally said that passengers were smoking in the compartment toilets, causing the train to slow down.

Smoke alarm sensors are now installed in vehicles such as trains, trains, and airplanes. During the driving of the train and the train, if the smoke sensor detects that there is smoke, it will send an alarm signal to the cab at the first time. At the same time, the in-vehicle control system will automatically cause the train to slow down or even stop. The occurrence of the situation.

Smoke sensors are used to detect the presence of smoke and smoke in the environment, such as detecting smoke during a fire. The smoke probe touches smoke or certain gases, and the internal resistance of the smoke probe changes, producing an analog value that is controlled. The smoke sensor uses the smoke sensor to transmit an analog signal corresponding to the smoke concentration to the host based on the principle that the concentration of smoke (mainly flammable particles) affects the resistance change.

Type of smoke sensor

Smoke sensors mainly include ionized smoke sensors, photoelectric smoke sensors and gas sensitive smoke sensors.

Ion smoke sensor

The smoke alarm uses ion smoke sensor inside. The ion smoke sensor is a technologically advanced, stable and reliable sensor, which is widely used in various fire alarm systems.

It has a radiation source ïÑ241 inside and outside the ionization chamber, and the positive and negative ions generated by ionization move to the positive and negative electrodes under the action of the electric field. Under normal conditions, the current and voltage of the internal and external ionization chambers are stable. Once there is smoke, escape the ionization chamber. Interfering with the normal movement of charged particles, the current and voltage will change, destroying the balance between the internal and external ionization chambers, so the wireless transmitter sends a wireless alarm signal to inform the remote receiving host to transmit the alarm information.

Such detectors produce charged particles (ions) by ionization of uncharged particles, so they are called ion smoke detectors.

The air between the electrodes is modulated by a DC voltage, which is generated by the source of the radiation source to form ions and generate current. After the smoke particles adhere to the ions, the current signal is attenuated and this signal change is proportional to the amount of smoke particles. The ion detector is suitable for the detection of open fires.

Photoelectric smoke sensor

There is an optical labyrinth in the photoelectric smoke alarm, which is equipped with an infrared pair tube. When the smoke is not smoked, the infrared receiving tube can not receive the infrared light emitted by the infrared emitting tube. When the smoke enters the optical labyrinth, the receiving tube receives the infrared through the refraction and reflection. Light, the intelligent alarm circuit determines whether the threshold is exceeded, and if an alarm is exceeded.

Photoelectric smoke detectors can be divided into dimming and scattering light:

1, dimming photoelectric smoke detector

The detection chamber of the detector is provided with a light-emitting device and a light-receiving device. Under normal circumstances, the light-receiving device receives a certain amount of light emitted by the light-emitting device; and when there is smoke, the light emitted from the light-emitting device is blocked by the smoke, so that the amount of light received by the light-receiving device is reduced, the photocurrent is lowered, and the detector sends an alarm signal. .

2, scattered light photoelectric smoke detector

The detection chamber of the detector is also equipped with a light-emitting device and a light-receiving device. Under normal circumstances, the light-receiving device does not receive the light emitted by the light-emitting device, and thus does not generate photocurrent. In the event of a fire, when the smoke enters the detection chamber, the light emitted by the light-emitting device is diffused due to the action of the smoke particles, and the diffused light is received by the light-receiving device, causing the impedance of the light-receiving device to change, thereby generating a photocurrent. The function of converting the smoke signal into an electric signal is realized, and the detector receives the signal and then determines whether an alarm signal needs to be issued.

The internal structure (probe cavity) of this type of sensor is provided with optical sensors (emission light source and photoelectric receiver). When smoke enters the detection cavity, it will block the emission of light and cause scattering. The photoreceiver will receive a signal that changes due to scattering of light. Then, a change in the current signal is generated.

Gas sensitive smoke sensor

A gas sensor is a sensor that detects a specific gas. It mainly includes semiconductor gas sensor, contact combustion gas sensor and electrochemical gas sensor, among which the most used semiconductor gas sensor. Its application mainly includes: detection of carbon monoxide gas, detection of gas, detection of gas, detection of Freon (R11, R12), detection of ethanol in exhalation, detection of bad breath in human body, and the like.

It converts the gas type and its concentration-related information into electrical signals, and according to the strength of these electrical signals, information about the presence of the gas to be tested in the environment can be obtained, so that detection, monitoring, and alarm can be performed; An automatic detection, control and alarm system can be formed by the interface circuit and the computer.

Among them, the gas sensor has the following types:

1. The flammable gas sensor element, including various kinds of alkane and organic vapor (VOC) gases, is currently widely used in range hoods, leak alarms and air fresheners;

2, carbon monoxide gas sensor sensor, carbon monoxide gas sensor can be used in industrial production, environmental protection, automotive, home and other carbon monoxide leakage and incomplete combustion detection alarm;

3, oxygen sensor, oxygen sensor is widely used, in the field of environmental protection, medical, metallurgy, transportation and other fields;

4. Toxic gas sensor is mainly used to detect environmental pollution gases such as flue gas, exhaust gas and exhaust gas.

A typical model for a gas sensitive smoke sensor is the MQ-2 gas sensor. The sensor is commonly used in home and factory gas leakage devices and is suitable for the detection of liquefied gases, butane, propane, methane, alcohol, hydrogen, smoke, etc.

Comparison of ionic smoke sensor and photosensitive smoke sensor

The ion smoke alarm is sensitive to the detection of tiny smoke particles and can respond to various smokes in a balanced manner. The forward photoelectric smoke alarm is sensitive to the detection of slightly larger smoke particles, and has poor response to gray smoke and black smoke. some. When a raging fire occurs, there are more tiny particles of smoke in the air, and when it is smoldering, there will be more smoke particles in the air.

If a large amount of tiny particles of smoke are generated after a fire, the ion smoke alarm will alarm first than the photoelectric smoke alarm. The two smoke alarms have a small time interval, but the spread of such fires is extremely fast. It is recommended to install an ion smoke alarm in such places. After another type of smoldering fire, a large number of slightly larger smoke particles are generated. The photoelectric smoke alarm will alarm first than the ion smoke alarm. It is recommended to install a photoelectric smoke alarm in such places.

Comparison of gas sensitive smoke sensor and ionized smoke sensor

Fire smoke is a mixture of gas, liquid, and solid particles, and has physical properties such as volume, mass, temperature, and charge. The ionized smoke detector is a microcurrent changing device that senses smoke particles by a voltage change caused by an ionization chamber corresponding to a smoke sensitive resistor. When the smoke particles enter the ionization chamber, the ionization state of the ionization chamber air is changed, so that the macroscopic expression is that the equivalent resistance of the ionization chamber increases to cause an increase in the voltage across the ionization chamber, thereby determining the smoke condition in the air.

While gas-sensitive sensors detect the composition of certain flammable gases in the air, gas-sensing sensors do not perform as well as ionic sensors in terms of fire detection. Detect the amount of flammable gas in the air. Effectively detect trace leaks of various combustible gases such as gas, liquefied petroleum gas, natural gas, and carbon monoxide. Applicable to petroleum, chemical, coal, electric power, metallurgy, electronics and other industrial enterprises, as well as gas plants, liquefied petroleum gas stations, hydrogen stations and other places that produce and store flammable gases.

Application of smoke sensor in fire prevention networking system

The connected smoke alarm uses a photoelectric or ionized smoke sensor to operate stably and reliably, and its performance is far superior to that of a gas sensor.

Networked smoke alarms can be used to alert smoke in a variety of early fires in a timely manner, with a small footprint and the ability to combine wireless launch and fire smoke sensors. Networked smoke alarms are mainly used in public places such as hotels, warehouses, hotels, restaurants, hotels, factories, oilfield wells, and movable board houses. When it is detected that the smoke in the air reaches a certain concentration, an alarm signal is immediately issued to effectively prevent fire, avoid loss of life, and loss of property.

The connected smoke alarm can be used alone. When using it, first fix its mounting base on the ceiling of the room to be monitored. Connect the battery to the alarm and screw it into the mounting base. In the working state, once the smoke concentration and duration of the prevention space are detected to reach the alarm value, the buzzer will sound an alarm immediately. When connected to a wireless burglar alarm system, the networked smoke alarm is installed and used as if it were used alone.

When the connected smoke alarm alarms, it will also send a wireless signal to the wireless anti-theft alarm host. The alarm host will respond to the alarm whether it is in the armed or disarmed state. This type of use, the scope of the alarm is wider, and the fire can be grasped in time when no one is in the house, so as to respond in the first time.

Application of smoke sensor in hotel fire automatic alarm system

The hotel is a place for domestic and foreign travelers to stay, eat and hold various meetings and banquets. Modern hotels generally have the characteristics of multi-functionality and comprehensiveness. They integrate catering, accommodation, entertainment and shopping, which is easy to cause fire. The automatic fire alarm system plays an important role in early detection of fires and early extinguishing of fires, minimizing the number of casualties, economic losses and adverse social impacts caused by fires.

For hotel buildings, in order to accurately predict the location of the fire and minimize the false alarm rate of the detector, a smoke detector and a temperature detector are selected to form a regional fire detector network. In the bedroom, study room, dining room and reception room, the detector with buzzer base is used. Any area detector in the room sends a fire alarm signal to the control room and triggers the buzzer to beep to remind the guests who are sleeping or working. Quick evacuation.

A smoke detector is a fire detector that utilizes a small smoke sensor to respond to smoke aerosols (solid or liquid particles) generated by combustion and/or pyrolysis suspended in the atmosphere surrounding it. There are generally ionic and photo-electric smoke detectors.

Taking a photoelectric smoke detector as an example, the photoelectric smoke detector has a smoke detecting chamber with a light source and a photosensitive element. The light of the light source generally cannot be irradiated onto the photosensitive element, but when smoke enters, the light is scattered in the smoke, so that part of the light hits the photosensitive element, and the more concentrated the smoke, the more light is scattered onto the photosensitive element. The photosensitive element then converts the optical signal into an electrical signal for output to the fire controller.

Key Applications of Vehicle Smoke Sensors in Automobile Fire Prevention

In recent years, car fire accidents have occurred from time to time, causing huge losses to the country and people's lives and property. The lesson is profound. At present, car fire accidents have become the focus of media public opinion, and the community has paid close attention to this.

In particular, urban buses and long-distance buses use people's air-conditioning systems to make people in a relatively closed environment, which brings a lot of inconvenience to fire treatment and personnel escape. It is especially important to control the occurrence of fires and early warnings. Therefore, to do a good job in fire prevention, we must rely on the use of high-tech anti-fire products in the field of automobiles, and find out and control the early stage of the disaster to eliminate the hidden dangers.

For the monitoring of fire smoke, smoke sensors and temperature sensors are mainly used, and the smoke sensors mainly include ion, photoelectric and gas sensitive types.

In recent years, with the development of gas sensing technology, the detection technology combining gas sensor and traditional fire detector has been widely used in the field of automobile fire smoke detection.
Because the gas combustion products are mainly CO and CO2 when the fire occurs, CO is a unique sign of very early fire. Because the content of CO in the air is extremely low in general, in the fire process, almost every substance has to be produced. Fully burning CO, especially in the smoldering stage, is even more so.

From the fire to the violent burning of CO experience from scratch, from small to large, and then gradually reduce the regular process of change, and CO is less dense than air, easier to float earlier to achieve early warning. Therefore, CO is suitable for early detection of fire, which is very important for capturing fire occurrence information at an earlier time.