Cause Analysis and Solution of False Alarm of Passive Infrared Detector

First, the principle of passive infrared detector

In nature, any object above the absolute temperature (-273 degrees) will produce an infrared spectrum. In the passive infrared warning zone, when no object moves, the pyroelectric infrared sensor senses only the background temperature when moving the object. Entering the warning zone, through the Fresnel lens, the pyroelectric infrared sensor senses the difference between the temperature of the moving object and the background temperature, and the alarm signal sent after the infrared signal change is converted into an electrical signal. The passive infrared detector itself does not emit in the infrared spectrum.
 

Second, the false alarm caused by equipment failure

1. Damaged faults. Including all failures and sudden failures of performance. Such failures are usually caused by damage to components or poor manufacturing processes (such as solder joints, false soldering, etc.).

2. Drift failure. It refers to the fault caused by the parameter of the component and the excessive drift of the power supply voltage. For example, if the temperature is too high, it will cause a change in the resistance value. At this time, the device behaves as good or bad.

Third, false alarms caused by environmental changes

1. The equipment is not installed securely and often moves to cause false alarms;

2. A false alarm is caused by the temperature change of the air conditioner and the ventilation fan;

3. Prevent the area door or window from being closed, and some people or animals may cause false alarms;

4. When the temperature difference between indoor and outdoor is large, the wind blows the curtain to cause false alarm;

5, multiple detectors simultaneously transmit signals, which can cause false negatives or interference (only wireless type);

6. The alarm system causes false alarms to other wireless infrared detectors. The device behaves as good or bad (only wireless).

Fourth, the solution

1. Install an infrared detector according to the installation requirements of the manual;

2. Avoid areas with strong temperature difference and air convection;

3. The doors and windows in the prevention area are closed, and the detector is normally turned on;

4. Close the doors and windows or bind the curtains;

5. Reduce the cross-detection range of the prevention area and avoid transmitting the alarm signal at the same time;

6, fast and accurate code, to prevent mis-recording information.

Five, the guarantee of low false positives

1. “0” misreported misleading products. To believe that PIR is a product of detecting sensors, there is no absolute “0” false positive product, and continuous optimization of technology can be used to reduce the frequency and frequency of false positives. The reason is that the infrared detector is only determined by the program set in the detector microprocessor in a specific environment and specific conditions. Sensitivity of detection is subject to changes in environment and conditions, and changes in the control environment are key to reducing false alarms.

2. CCC certification. CCC compulsory certification of qualified products is a must, and high-quality electronic components, strict quality system maintenance, credible quality commitment and perfect after-sales service are also selected.

3, multi-technology combination discrimination to improve the reliability of the detector, the current products are: passive infrared detector, microwave + passive infrared double detector, voice + vibration glass broken double detector, ultrasonic + passive infrared double detector Wait.

4. Special circumstances. Some environmental noise double detectors can't do anything, for example: mice in the guard zone; pets walking around the room. To this end, the scientific and technical personnel have introduced the micro-processing technology into the alarm system, so that it has certain identification and logical discriminating ability, and can judge to some extent whether it is an intruder or an environmental noise-caused alarm.