In the community security construction, the perimeter defense alarm system is the most important core part. From the point of view of the characteristics of the security system setting, the perimeter of the community is mainly composed of the perimeter wall of the community, the shops along the street and the community buildings, which together form the perimeter of the whole community, and some buildings are adjacent to the shops. Therefore, it is necessary to achieve comprehensive protection of perimeter, intrusion alarm, and security video surveillance. With the development of the Internet, the network electronic fence is becoming a product of more and more community perimeter defense.
Using the network electronic fence as a perimeter guard has the following advantages:
Physical barrier: According to different installation methods, the front fence forms barriers that are insurmountable at different heights in the perimeter of the cell, and the spacing between the front end alloy wires is between 120 and 200 mm, which increases the intruder's climb or traverse from the wire. Difficulty. In addition, fences and warning signs have a deterrent effect on intruders, which can effectively reduce their criminal motives.
Electric shock defense: When an intruder climbs or destroys the front fence, it can generate a 5KV~10KV pulse voltage. It can use the electric shock to suppress the deterrent or forcefully terminate the intrusion, but the current is small and will not cause serious accidental accidents. Suitable for the community, such a complex household category, better protection for the elderly and children.
Detection alarm: Monitor the front-end fence to output an alarm signal when abnormal conditions such as short circuit, open circuit or attempt to destroy, and ensure the daily normal work, while the false alarm rate is very low, which can prevent the community security personnel from being irritated and close the perimeter alarm system. The land guarantees the safety of the residents in the community.
Hierarchical management: The system can divide the authority according to the actual situation, realize hierarchical management and adjustment, such as arming and disarming the electronic fence, high and low voltage conversion; setting camera preset position, lens switching, etc.
Alarm linkage: support multi-system linkage with video, lighting control, broadcasting system, etc., to fully protect the security of community residents.
What sensors are there in the perimeter security?
In the network electronic fence, the sensor is a very fine part of the electronic fence for security maintenance alarms. So which sensors are used in the perimeter security?
Perimeter security sensors are mainly divided into two types: interference type and non-interference type; most of the sensors are mainly non-interference type, and fiber optic sensors become the mainstream products in the future. The following is a detailed analysis based on the working principle of different sensors.
Interferometric sensors are mainly phase-modulated fiber-optic sensors. Their optical phenomena are mainly interference, such as magnetostriction, electrostriction, Sagnac effect and photoelastic effect. Magnetostrictive detection features mainly current and magnetic field, electrostriction Power plant, voltage, mainly from the name can be seen the difference between the two.
The Sagnac effect depends on the angular velocity; the photoelastic effect detection features many, such as vibration, pressure, acceleration and displacement; the most traditional interference is determined by temperature, which is the basis of detection.
There are three main representatives of non-interferometric sensors: intensity-modulated fiber temperature sensors, polarization-modulated fiber temperature sensors, and frequency-modulated fiber-optic temperature sensors.
The intensity-modulated fiber-optic temperature sensor is rich in optical phenomena, and the light-shielding plate blocks the optical path, changes in semiconductor transmittance, fluorescence radiation and black body radiation, fiber microbend loss, reflection of diaphragm or liquid crystal, gas molecule absorption, fiber leakage film, and the like. Intensity fiber temperature sensing relies mainly on temperature measurement, in addition to vibration, pressure, displacement, and so on.
Polarization sensing optical phenomena are Faraday effect, bubbler effect, birefringence change, and photoelastic effect, which are measured as current, magnetic field, spread, temperature, acceleration, and displacement, which are similar to phase sensing effects.
Frequency sensing is relatively special, and its optical phenomena are Doppler effect, stimulated Raman scattering, and photoluminescence, which are measured as velocity, flow rate, gas concentration, and temperature.
Fiber optic sensing alarms have high accuracy, so military bases, borders, etc. will use this detection mode. All outdoor equipment is passive, no need for field power supply, and can provide effective perimeter security monitoring. If you install such an alarm system around your home, it would be a bad day, but this is not the price that ordinary residential properties can accept.
The higher the sensitivity of the sensor, the better?
In our usual anti-theft applications, most users use sensitivity as an important reference for their device performance. And if the sensitivity of a certain anti-theft device reaches a very high level, many people will think that the anti-thief effect under this device will not be too small. Technically speaking, only when the device maintains a higher sensitivity, the value of the output signal corresponding to the measured change will be larger, which may be more advantageous for signal processing. Therefore, from this perspective, the sensitivity of the sensor is naturally higher as possible.
However, we can't ignore another problem: as the sensitivity of the sensor increases, the surrounding scenes that are not related to the scene being measured are more introduced, and are continuously amplified as the sensitivity increases. Such a result will eventually have a lot of adverse effects on the accuracy of the measurement. Therefore, high sensitivity is definitely an aspect that we need to pay attention to but cannot blindly chase.
For sensors, their sensitivity is directional. When the measured is a single vector, and its directionality has higher requirements, we do not need other sensors with less sensitivity. And if we are measuring multidimensional vectors in the needs of shooting, we need to focus on sensing devices with small cross sensitivity. It can be seen that high sensitivity is not necessarily a high-end configuration that always scented.
Is the accuracy as high as possible?
The accuracy of the device is another important indicator for determining the characteristics of the sensor. In the alarm sensing work, the accuracy can be said to be an important part of the accuracy and timeliness of the entire measurement system. Therefore, the accuracy of the sensor is also an important aspect that we cannot ignore.
However, the accuracy of the sensor must be selected high? For the technical application of sensors, higher precision equipment often means higher prices. Is it only the high-end price to ensure that we enjoy our equipment more practically? Or, how can we grasp our needs?
In fact, if our measurement needs are relatively constant, we only need to choose a relatively cheap, more repeatable sensor, and not necessarily choose a more expensive high-end product. Of course, if we want to do quantitative analysis or have higher alarm detection requirements, then we must use more accurate equipment to meet our application.
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