Analysis of Intrusion Detector's False Positive Factors and Solutions

The ideal intrusion detector merely responds to the presence of personnel, and does not respond to the activities of animals such as dogs, cats and mice, and does not respond to changes in the indoor environment such as changes in temperature, humidity, and wind, rain, and vibration. It is not easy to do this, most devices not only respond to people's existence, but also respond to the influence of some unrelated factors.

Alarms issued when there are no intrusions are called false alarms. False positives may be caused by component failures or some external influences. The adverse consequences it produces are disastrous. The lightest consequences are annoying because of the increase of many unnecessary troubles, which greatly reduces the possibility of alarms. Reliability. The worst consequence is that it allows the police or security personnel to rush to the scene unnecessarily, so that their own safety and the safety of people around them will be endangered. Therefore, false alarm is the fatal weakness of the alarm.

Let us analyze the main reason that infrared detection alarms may cause false alarms. At present, there are several reasons for false alarms in the alarm system. The poor performance of the wireless detectors in terms of anti-jamming performance is likely to cause false alarms due to the same frequency interference. Infrared detectors cause false alarms due to inaccurate judgment in intrusion behavior. Infrared detectors are vulnerable False positives due to environmental factors such as temperature and light.

Because the host and the detector are using wireless coding to set the code to have duplicates, causing host and detector re-encoding to cause false alarms; some alarms also have poor quality, such as component damage and poor production process, causing false alarms; The selected equipment, installation method, angle, location, and also related; as well as under the influence of the environment such as air movement, pet actions, etc., as well as human factors, mainly due to improper operation of the user, accidentally triggered the alarm, misunderstanding False positives may be generated by mistakes such as mistakenly entering a defended area.

The reasons for false positives are many and complex. Therefore, the most important thing to reduce the false alarm of burglar alarm is to consider it from many aspects, such as selecting the detector from the aspects of technology and performance, including the choice of the sensor detector, the external design of the Fresnel lens, and micro-processing. Program, multi-technology, automatic code skipping coding technology, production process, use methods, temperature compensation, sensitivity detection distance adjustment and so on. These comprehensive factors determine the detector's performance and false alarm rate.

The new-generation infrared detectors designed for the above situations adopt some unique technologies to solve such problems. First of all, in the focus of the infrared lens, two photothermal sensors connected by different circuits are applied. The special lens divides the coverage area into multiple protected areas with a trapezoidal sensitivity and guarantees the signal strength in the protected area. The unique lens also acts as an infrared Filter, and the specially treated black lens on the surface allows visible and shortwave infrared (which exists in most white light sources) to be injected and then absorbed by its black base. The black infrared lens reflects only the infrared rays whose wavelength matches the body's movement and reflects it to the photothermal sensor. With a white filter, the detector can prevent white light interference. If someone enters or leaves one or more areas covered by the detector, the detector should detect changes in the infrared radiation energy, and the A/D converter digitizes the signal sent from the sensor and then analyzes it with the processor. Then it will send an alarm signal.

This process involves all the criteria in the probe, such as signal amplitude, time, format, energy, and spectrum, plus statistical information actually extracted from the site. These criteria must be combined with the judgement to detect their rationality. The detector will not issue an alarm until the results meet the criteria for forced entry. Digitizing the signal of the photo-thermal sensor eliminates signal transients and electromagnetic interference.

Currently, Shuangjian detectors occupy a certain share in the market, and microwaves are insensitive to changes in temperature and light. Through the combination of two detection units, the detector's intelligent Shuangjian passive infrared detector has greatly reduced the possibility of false positives. Sex.

The sensitivity and reliability of the alarm detectors influence each other. Reasonably selecting the detection sensitivity of the alarm detector and adopting different measures against external interference can improve the performance of the alarm detector. The use of different anti-jamming measures determines the performance of the alarm detector in different environments. Understand the performance and characteristics of various alarm detectors. According to different use environments, rational allocation of different alarm detectors is the key link of an anti-theft alarm system. Various detectors have different working principles. Each has its own advantages and disadvantages. To make the detector work effectively in any situation, it should be carefully selected and carefully installed.