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There are two Fresnel lens functions: one is the focusing effect, that is, the pyroelectric infrared signal is refracted (reflected) on the PIR, and the second function is to divide the detection area into several bright and dark areas to enter the detection area. The moving object can produce a varying pyroelectric infrared signal on the PIR in the form of a temperature change.
What is dual-inspection technology?
According to the Doppler principle in physics, we know that microwaves are transmitted at one frequency, and when there are moving objects within the range covered by them, they will be reflected at another frequency, so that there is a frequency difference between the transmission frequency and the reflection frequency. In this way, the size of the change can be detected to know the volume and movement speed of the person, combined with the signal detected by the infrared, and the two CPUs are used to calculate the two trigger signals, and the relevant characteristics of the signal are comprehensively analyzed to determine whether there is any Intruder. The double false detection has a low false positive rate. In addition, because of the double comparison, the infrared detection can be adjusted to a higher sensitivity, thereby overcoming the near-body temperature effect, that is, when the room temperature is close to the human body temperature, the detector can still work normally.
What is the three-inspection technology?
Due to the influence of the external environment on the detector, the detector may be falsely reported in the case of strong winds, sunlight, birds or other small animals. Therefore, the detectors are generally installed in an indoor environment. However, this will only trigger an alarm when the intruder enters the room. It cannot really effectively block the intruder from the door. Therefore, there is an urgent need in the market for a detector to be able to pre-alarm before the intruder enters the room. Move and block the intruder outdoors, this is an outdoor type of detector. Since the outdoor environment has many influencing factors, the outdoor detector has higher anti-false alarm capability than the general detector. Two or even three infrared sensors are used inside the detector, which adopts a double-window structure. When these sensors are judged to have a real human body invasion, they will alarm. This technology can not only resist glare (≥1 million Lux, tens of thousands of Lux for general outdoor detectors), but also resists the influence of strong winds, small animals, external noise and various harsh climates, and truly meets outdoor prevention. Claim.
What is a double curtain technology?
The direction recognition curtain generally consists of a double curtain, which is divided into an inner curtain A and an outer curtain B. When the owner walks from inside to outside, first triggers the inner curtain A, and then triggers the outer curtain B. At this time, the detector does not alarm; when the intruder breaks in from the outside, the outer curtain B is triggered first, and then the inner curtain is triggered. A, the detector immediately alarms. When the head of the household goes out and returns to the room, the front curtain B is triggered first and then the inner curtain A is triggered. For this reason, the return of the head of the household needs to be distinguished from the invasion of the outsider. The detector will delay the alarm time after the head of the household to ensure the head of the household. No alarm when returning. The curtain detector is generally used to prevent entrance and exit areas such as windows and balconies. However, after installing the general curtain detector, the owner may trigger the detector alarm when entering or leaving the balcony, and the activity space of the head of the household is greatly restricted. The direction recognition curtain detector solves this problem.
What is the four curtain technology?
The composition of the four curtains is the same as that of the above-mentioned double curtains, and has a direction recognition function. However, it adopts digital signal processing circuit (DSP) and applies three-vector digital orthogonal analysis technology to more accurately identify the moving direction of other people's body and further improve the accuracy of direction recognition.
What is the principle of a passive infrared detector?
The so-called passive infrared detector has only an infrared receiver. When there is a target intrusion and movement within the scope of protection, it will cause changes in infrared radiation in the area, and the infrared detector can detect the change of the infrared radiation and issue an alarm signal. In fact, in addition to the infrared radiation emitted by the invading object, other objects in the detected range, such as outdoor buildings, terrain, trees, mountains and indoor walls, desks, furniture, etc., will radiate heat, but because these objects are fixed Varying, the thermal radiation is also stable. When the invading object enters the monitored area, the stable thermal radiation is destroyed, and a changing thermal radiation is generated, which is induced by the pyroelectric lens and the pyroelectric infrared sensor. It is the difference between the temperature of the moving object and the background temperature, and the alarm signal sent after the infrared signal changes into an electrical signal.
What is the principle of an active infrared detector?
The active infrared detector consists of two components, an infrared light emitter and a receiver. One end emits infrared rays, and the infrared rays received at the other end form a loop through the infrared rays. The active infrared emitter emits a modulated infrared beam that is directed at the infrared receiver to form a warning line. When the target invades the warning line, the infrared beam is partially or completely blocked, and the receiver receives a signal change and alarms.
Several working modes and principles of the excellent infrared detector
The working mode can be divided into: power saving mode (12 seconds continuous detection) and normal mode (10 seconds). Principle: After the infrared detector senses the moving human body, it immediately transmits the first alarm signal. After 10 seconds, it automatically transmits the second alarm signal. The power saving mode: infrared detector
After detecting the human body signal for the first time, if the human body signal is detected within 12 seconds, if the alarm signal is not transmitted, the human body signal must be detected for more than 12 seconds, and the alarm signal is sent once, which can greatly save power and reduce False alarm rate.
What factors in the environment should be considered when installing an infrared detector?
When the active infrared detector is used for indoor warning, the work reliability is high. However, when used for outdoor warning, it is greatly affected by the environmental climate. Since the lens surface of the optical system is exposed to the air, it is easily contaminated by dust and the like. However, the cordon or warning network formed by the active infrared detector can be randomly configured according to different environments, and is flexible and convenient to use.
Passive infrared detectors are space-controlled detectors. Due to the poor penetration of infrared rays, there should be no obstacles in the monitoring area, otherwise it will cause a "blind area". In order to prevent false alarms, the passive infrared detector probe should not be aimed at any object whose temperature will change rapidly, especially the heating element. The detector should have a maximum warning range so that possible intruders can be within the beam range of the infrared alert. And the intruder's activity is beneficial to laterally traverse the beam band, which can improve the sensitivity of the detection. However, when several passive infrared detectors are installed in the same room, there is no mutual interference.
How to detect the cause of the detector not alarming?
Use the walking detection method to trigger the detector to see if the detector indicator flashes. If it is not lit, it indicates that the battery needs to be replaced. If it indicates that the detection function is good, the host does not receive it. Cause 1 The battery is low, cause 2 The detector is partially defective. , cause 3 host receiving part of the bad.
How is the detection distance of the microwave infrared dual detectors adjusted?
The infrared detection distance is changed by shorting the jumper. The detection distance of the connected jumper infrared is reduced by 50%. The detection distance of the microwave is changed by adjusting the potentiometer on the lower right leg of the circuit board. The detection distance is smaller in the direction of the MIN, and the detection distance is larger in the direction of the MAX, and the corresponding adjustment is made according to the situation on the spot to meet the use requirements.
What issues should I pay attention to when installing the host?
The host should be installed away from large metal objects, TVs, computers, etc., otherwise the transmission or reception distance will be shortened because the signal is interfered; the host should be installed close to the detector as much as possible; under the premise of concealment, the antenna should be pulled out as much as possible. Raise; pay attention to the phone incoming and outgoing positions are incorrectly inserted.
Host maintenance and maintenance
For each power tool, there are usually two carbon brushes to choose from: With automatic stop and without automatic stop. Carbon brushes with automatic stop have a spring through the length of the carbon brush. When the carbon brush wears out, the spring gets released, the current to the carbon brush gets interrupted and your power tools switches off at once. The advantage: No additional wear and tear to your power tool. Carbon brushes without automatic stop do not stop functioning at once, but performance of your power tool will detoriate rapidly. Although handy as a warning sign, this usually isn't very beneficial to your power tool.
Knowledge and answer about burglar alarm
[ Huaqiang Security Network News ] The development of anti-theft alarm , the security industry occupies a very market, there are also many technical problems, we will give you a one-on-one answer here. What is a Fresnel lens?