Explanation of alarm terms (3)

Microwave technology: According to the Doppler principle in physics, we know that microwaves are sent at a frequency, and there is a change in the size of the coverage area to know the volume and moving speed of the person, combined with the infrared detected signal, while The internal CPU chip performs algorithm processing on the two trigger signals, analyzes the relevant characteristics of the signal, and finally determines whether there is an intruder in the viewing zone.

Curtain technology: Curtain technology means that the area where the light can be refracted by the Fresnel lens to the detection point of the sensor is two fan-shaped curtain regions, and the angle between the two curtains is about 6 to 9 degrees.

Sanjian technology: Sanjian technology refers to the use of three different detection methods to achieve information confirmation. Currently, active infrared + passive infrared + microwave technology is more popular. With the development of laser detection technology, some companies have begun to use laser technology to Realize detection.

Pyroelectric sensor: The pyroelectric effect is similar to the piezoelectric effect. It refers to the phenomenon that when the crystal is heated to produce a temperature change, its atomic arrangement will change, and the crystal will naturally polarize, generating charges on its two surfaces. Pyroelectric sensors are sensors that are sensitive to temperature. It is composed of ceramic oxide or piezoelectric crystal elements. The electrodes are made on both surfaces of the element. When the temperature changes within the monitoring range of the sensor by ΔT, the pyroelectric effect will generate a charge ΔQ on the two electrodes. A weak voltage ΔV is generated between the two electrodes. Due to its extremely high output impedance, there is a field effect tube in the sensor for impedance transformation. The charge ΔQ generated by the pyroelectric effect will be combined with the ions in the air and disappear, that is, when the ambient temperature is stable, ΔT = 0, the sensor has no output. When the human body enters the detection area, due to the difference between the human body temperature and the ambient temperature, ΔT is generated, and there is ΔT output; if the human body does not move after entering the detection area, the temperature does not change and the sensor has no output. So this sensor detects human or animal activity sensing.

Power-on self-test: After the detector is connected to the power supply (wired is 12V and wireless is 3V), the CPU will detect whether the surrounding circuits are normal for the first time, and the detection time varies from 120 seconds to 150 seconds. If the circuit is not normal, the detector will give an alarm.

Fresnel lens: The Fresnel lens has two functions: one is the focusing effect, that is, the pyroelectric infrared signal is refracted (reflected) on the PIR, and the second function is to divide the detection area into several bright and dark areas , So that the moving objects entering the detection area can generate a changing pyroelectric infrared signal on the PIR in the form of temperature changes.

Lens window: The lens window here refers to the subdivided interval in the Fresnel lens. The more windows, the higher the degree of subdivision of the detection area, which is related to the manufacturing process of the product and the mold.

Sensing distance: the maximum distance that the detector can detect.

Anti-interference technology: refers to the anti-interference performance mentioned in the manual of each type of detector, such as anti-pet technology, anti-wind, anti-sunlight, anti-high temperature, etc.

Low-many dual-element structure: low-noise dual-element infrared detector, composed of positive and negative two detection elements, only after both positive and negative detection elements are triggered, the detector judges whether to alarm, using this principle can be accurate Distinguish between moving and non-moving signals, plus the noise generated by the positive and negative detection elements can cancel each other out, thus making the false alarm rate lower than that of the single source structure.