Analysis false alarm for intrusion detectors and solution

The ideal of intrusion detectors should only be triggered when detect the human (intruder), it should not be triggered when detect the movement of dogs, cats and mouse, as well as changes of environment of temperature, humidity, wind, or raining or sounds…etc. To achieve this purpose is not easy; most of device not only can be triggered by the movement of human, but also triggered by other factors.

Without intrusion caused alarm we call false alarm. False alarm can be caused by the device defects or other factors of environment. False alarm cause un-necessary trouble and drive people crazy, as well as reduced the trust credit of burglar alarm systems. The worst result is push the police man or patrol guard in a hurry to arrive the scene. In a nutshell, false alarm is the fatal defect for burglar alarm systems.

Let’s analysis the factors caused false alarm for PIR motion sensor. Typically there are several factors that can cause the false alarm: Wireless PIR motion sensor without the anti-interference from the same wireless frequency; PIR motion detectors without enough accurate to judge the true intrusion (movement by human); PIR motion sensor can be triggered false alarm by the changes of environment, sunlight…etc environment factors; Due to most of wireless alarm system and wireless sensors adopt the wireless code technology for the communication, there is high ratio of duplicate code, it can cause the false alarm. False alarm can be caused by the defect of component inside of detectors, also related to the installation method, angle, position, and environment of air flow, pet…etc, also with human-made false operation, carelessness to trigger the alarm, friendly intrusion…etc.

False alarm can be triggered by many factors, and it’s too complicated. We need to take all factors into consideration to reduce the false rate, for example: choose the detectors according to the technology and performance, include sensor choosing, Fresnel lens housing design, MCU processing, Dual Sensor detection technology, Learning code technology for wireless transmission, SMT, Temperature compensation, Sensitivity adjustment…etc. These factors determine the performance of detector and false alarm rate.

Nowadays, Dual tech PIR Motion detector dominate part of market share, Microwave doesn’t sensitive to the changes of temperature and sun-light. Through combine Microwave sensor (or Doppler radar) and PIR (passive infrared) technology, Dual Tech PIR motion detector can reduce the false alarm effectively.

Choosing the best detectors and adopt different anti-interference methods can improve the stability of performance for alarm systems. Different anti-interference methods can insure the working of intrusion detectors under various environments. To fully understand the performance and features for the intrusion detectors, and according to the different using environment, reasonable configuration is primary procedures for the burglar alarm systems. Different intrusion detectors with diverse working theory, with different advantages and disadvantages, in order to make them work properly, we need choose and install them carefully.