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1 passive infrared detector infrared detection basic concept <br> <br> in the warning range, why people passive infrared detector alarm signal can occur when you move it?
In nature, any object higher than the absolute temperature (-273 degrees) will produce an infrared spectrum. At different temperatures, the wavelength of the released infrared energy is not the same, so the infrared wavelength is related to the temperature.
There are two key components in the PIR detector. One is a pyroelectric infrared sensor (PIR). It can convert the infrared signal with a wavelength between 8 and 12um into electrical signals and can be used in nature. The white light signal has an inhibitory effect. Therefore, in the vigilance zone of the passive infrared detector, the pyroelectric infrared sensor senses only the background temperature when there is no human body moving. When the human body enters the vigilance area, it passes the Fresnel lens and heats. The infrared sensor senses the difference between the human body temperature and the background temperature. Therefore, the basic concept of infrared detection by the infrared detector is to sense the temperature difference between the moving object and the background object. Another device is the Fresnel lens, Fresnel lens has two forms, namely refractive and reflective. The Fresnel lens has two functions: one is focusing, that is, the infrared signal of pyro is refraction (reflection) on the PIR. The second function is to divide the alert area into several bright and dark areas so as to enter the alert. The moving object in the area can generate a change pyro-infrared signal on the PIR in the form of a temperature change, so that the PIR can generate a changing electrical signal.
Moving the infrared detector 2 warning area sensor Model <br> <br> in any one of the PIR sensor model has its factory specification viewport FIG.
What information can we learn from this model?
The height at which the detector should be installed. â— The angle of view of the detector under the viewport should be â— The farthest guard range. â— The widest guard action distance. â— The guard angle. â— The direction of the visual sensor. With this information, you can detect the passive infrared. The device has a basic understanding and will be very helpful for the correct use of passive infrared detectors.
About 3 passive infrared detector anti-pet function <br> <br> passive infrared detectors to today, technically mature, anti-small pet is a passive infrared detector important functions, each manufacturer The treatment of confronting small pets is different, but there are two ways: one is the physical method, which is to reduce the probability of false alarms caused by small pets by changing the fresnel lens's segmentation method. This method is superficial and the effect is also limited. The second way is to use probing signal processing and analysis. Take AS-910DT of our company as an example, it is mainly to collect data of the detected signal, and then analyze the signal cycle, amplitude and polarity.
These factors specifically reflect the speed of the moving object, the amount of heat released infrared energy, and the displacement per unit of time. The microprocessor in the detector analyzes and compares the collected data to determine whether the moving object may be a human or a small animal.
From this point of view, we must pay attention to the function of the PIR-detector's anti-small pet is relative. This kind of relativity includes two aspects. One is that the prevention of pets is relative, and the false alarm rate is greatly reduced compared to the detector without the pet protection function. It has a certain limit on the number and size of small pets. The second aspect is that the installation location must have certain requirements. It is not a random installation that can achieve the function of preventing pets. When installing, it is necessary to carefully understand the specific requirements of the detector's instructions.
Microwave detector principle <br> <br> 4 Dual Technology detector Doppler principle in physics tells us that in the microwave band, when in a transmit frequency in the range of microwave energy, although covered, when When there is a moving object, it will be reflected at another frequency so that there is a frequency difference between the transmission frequency and the reflection frequency. This frequency difference is related to many factors, including the speed of the moving object, and the radial angle of the detector. The principle of microwave detection is theoretically more complicated. However, in the Shuangjian detector, in addition to understanding the basic concepts of microwave detection, we also need to understand that the propagation of microwaves has a penetrating effect on buildings. Therefore, if Shuangjian detectors are installed indoors, if the sensitivity is adjusted improperly It is possible to radiate outdoors, which may cause false alarms.
Passive infrared detector 5 mounted <br> <br> Considerations Because passive infrared detector is a kind of weak signal detection apparatus, the installation must pay attention to some of the details of the problem, such as high sensitivity and the like. Correct installation of a passive infrared detector, you must master the following aspects of information: First, the performance characteristics of the detector must be understood, and secondly, a reasonable position to determine the installation, and finally must be carefully adjusted. It cannot be said that the detector can be alarmed to indicate that it is installed. How to determine the installation position of a passive infrared detector?
* According to the instructions to determine the normal installation angle Mounting height is not arbitrary, it will affect the sensitivity of the detector and the effect of preventing pets. Imagine a detector mounted at a height of 2M and a height of 2.5. When the moving object moves from the ground, the frequency of cutting the bright area and the dark area is different.
* Should not face the glass doors and windows Passive infrared detectors are facing the glass doors and windows, there will be two problems: First, white light interference, apparently PIR has a strong suppression of white light, but after all, is not 100% inhibition. So avoid facing the glass doors and windows, you can avoid strong light interference. The second is to avoid complex environmental disturbances outside doors and windows, such as crowd movements and vehicles.
* It is not appropriate to have a close relationship with the change of temperature for the passive infrared detectors of hot and cold vents or cold and heat sources. Hot and cold vents and cold and hot sources may cause false alarms. For some low-performance detectors, air convection through windows and doors sometimes causes false alarms.
* It is not appropriate for objects that are easily oscillating on objects that are easy to oscillate to make microwave detectors work. Therefore, false alarms may also be caused. The ancient attention to the purpose of installing detectors on the illegal invasion route was sufficient to prevent the criminals from making illegal intrusions. Before determining the installation location, it was necessary to consider the main population of buildings. In fact, we have prevented entrances and exits and intercepted illegal intrusions. This has achieved our goal.
* Reasonable selection of passive infrared detectors with a variety of models. For example, our company's Oram ALARM series, from 10 meters to 25 meters, from dual infrared to dual Kam, from pet-proof to shelter, from wall-mounted to ceiling-mounted, then the detector to be installed Must consider the actual situation such as preventing the size of the space, the surrounding environment, the characteristics of entrances and exits. Sometimes consider replacing models to meet requirements.
6 Commissioning <br> <br> After installing the detector, the detector is the final commissioning work to be done. There are two methods for the commissioning of passive infrared detectors. One is the step-by-step measurement. The commissioning personnel walks the s-type line in the alert zone to sense the length of the alert range, which can be understood from the figure.
Microwave sensitivity and infrared sensitivity should be adjusted separately by step-by-step method. Too high or too low sensitivity will affect the prevention effect. Sometimes due to seasonal changes, sensitivity is adjusted separately in winter and summer. Microwave sensitivity must not be too large, because microwaves are only penetrating, and care should be taken during commissioning.
The second method is meter measurement. Some detectors have a background noise voltage output interface, such as the Orem ALARM detector, which is tested with the voltage of the multimeter. When the detector is in alert state, the output voltage of its static background noise is The size of the interference indicates the degree of interference from the source of the interference to determine if this location is suitable for the installation of such detectors.
The above part is just an analysis of the basic commonality of the use and installation method of passive infrared detectors by the author. It is based on the product technology of Dixon. Each brand has its own unique method in infrared processing, so we are using installation. Before, we must read the instructions carefully. The most important thing is that through the accumulation of actual work experience, the characteristics of the detector must be able to have a deeper understanding, so as to better play the role of passive infrared detectors in security engineering.
Application of Aurum ALARM infrared detector
Passive infrared detectors are a type of detector that is most commonly used in security engineering. However, for its normal use, it is necessary to prevent omissions, but also reduce false positives. In particular, how to reduce the number of false positives to the minimum is a subject that is facing the majority of engineering designers. To achieve this, we must first understand some of the basic concepts and technical characteristics of passive infrared detectors, so that in accordance with these basic technical characteristics, from the installation, debugging, use and other aspects, in accordance with the basic technical characteristics of the detector, In order to maximize the detector's maximum efficiency.