What’s difference between wide angle PIR and curtain PIR ?
Firstly, all the motion detectors mentioned above are PIR-based, all with the primary function of detecting temperature changes.
Working Theory:
In nature, any object with an absolute temperature above -273°C emits infrared waves. Different temperature objects emit different wavelengths of infrared radiation, hence the wavelength is related to the temperature.
PIR-based motion detectors consist of two main components:
- PIR Element Sensor: This sensor converts infrared waves in the 9-12µm range into electronic signals and is inherently resistant to white light interference. Without human movement, the PIR sensor only detects the background temperature. When a human enters the detection area, the PIR sensor, through a Fresnel lens, can detect the temperature difference between the human and the background.
- Fresnel Lens: There are two types of Fresnel lenses: refractive and reflective. The Fresnel lens focuses and directs infrared waves to the PIR element sensor. It also divides the detection area into dark and white zones, allowing the PIR sensor to easily identify temperature changes when a moving object enters the detection area.
The major difference between wide-angle PIR-based motion detectors and curtain PIR-based motion detectors lies in the detection angle and width.
- Wide-Angle PIR-Based Motion Detector: These detectors have a wide detection angle of 100-120 degrees horizontally and 60 degrees vertically, with a conical detection space of 8-12 meters. They are typically used for interior movement detection.
- Curtain PIR-Based Motion Detector: These detectors use specialized Fresnel lenses to create a very narrow detection space, around 15 degrees. They are usually installed in front of windows, protecting only the window area. People can move inside the house without triggering the alarm.
Direction Recognition Curtain PIR: This type of curtain PIR-based motion detector includes direction recognition. It will not be triggered when a person walks directly forward in one direction but will be triggered when movement is detected in the opposite direction.
The advantage of this feature is evident when installed on a balcony door. If the house owner goes to the balcony and returns within a preset time (which can be set on the detector), the detector will not be triggered. However, if someone tries to enter the balcony from outside, the alarm will be triggered.
