[source] Shenzhen Yuan Li author [China security industry network]
The passive infrared detector is a weak signal detection device, so some details of the installation of the possible effect of detection will directly affect the detector, so it was installed on the angle and the height of what are the requirements? What are the wrong places to install?
A large extent detector sensitivity, range and the installation height of a direct relationship between the optimal installation of passive infrared detector height of 2.1 meters to 2.5 meters, if it is anti PET detector, so its installation height requirements will be higher. If the charge is too high, as the blind will, if it is too low and could not detect the location for the distance, so the practical application also need to step out.
For example, the same curtain passive infrared detector is a kind of principle, if you need to install in the window, when the installation height is from 25CM on the windowsill, if too high, they can be drilled in the past from below detection, if the distance is too low it is possible to cross over from above.
The principle of passive infrared is to monitor the temperature difference. When the outside temperature is about 37 degrees, it is basically out of order, so don't install it near the heat source. In addition, the need to pay attention to avoid the opening of air holes, air conditioning, radiators and other environmental variables can change the temperature of the region, but also pay attention to the middle of the shelter (even transparent, such as glass) occlusion.
Also, avoid electric fans, sun hanging clothes, curtains and other easy to move objects. Frequent animal activities should also be avoided, and if the actual need is unavoidable, then pay special attention to the use of anti pet detectors.
Sensitivity is the most direct factor that affects the detector's false positive rate or false negative rate. How can the sensitivity be adjusted so that the false positive rate and the false negative rate can achieve the desired effect?
In conventional detection, the sensitivity is a contradiction between false positives and false negatives, false positives and lower sensitivity to reduce, will bring up the issue of false negatives; on the contrary, in order to reduce the false negatives and high sensitivity, and will bring up the issue of false positives. It is difficult to accurately grasp the "degree" in practical applications.
The specific setting of sensitivity should be determined according to the actual environment. Generally speaking, if the application environment is bad, for example, there are often birds or leaves floating objects such as blocking the beam, it should be set in a low sensitive file. Active infrared detectors should choose the right response time: too short to cause unnecessary interference, such as birds flying over, small animals passing through, etc., too long will fail to report. The minimum duration of shading is usually measured at speeds of 10 meters per second.
Sometimes the sensitivity is adjusted in winter and summer due to seasonal variations.
