United States
With installed motion detectors at home, you expect an instant response to intruders. If a thief steps over the threshold or breaks in through the window, an alarm will be triggered. And you can rest assured that any high-quality alarm device can handle this task. But responding to motion is only half the battle: an important quality of a detector is the ability to determine what exactly is moving. It must quickly and accurately detect a person, while also ignoring the natural interference and pets, so that you and the security company are sure: if the security system has activated the alarm, the threat is real and you need to respond immediately.
This article tells how infrared motion detectors see the world, what technologies they use to distinguish a sheepdog from a villain, and what animal owners should remember when installing a security system at home.
How infrared motion detectors work
Motion detectors based on infrared sensors pick up infrared radiation or, in other words, the heat.
Sometimes they say: “The motion detector saw a human”. However, these devices do not see objects, animals, or people; in fact, they only deal with data.
A special curved Fresnel lens focuses infrared radiation onto the detector’s IR sensor. Then the sensor signals are sent to the microprocessor, which converts them to digital data. This is followed by threat analysis and assessment, which is precisely the key difference between smart detectors and their primitive counterparts. Knowing the intensity of infrared radiation and the dynamics of the source movement, software algorithms determine the nature of the threat, and the detector decides whether to raise an alarm or ignore it.
How pet immunity is implemented in Ajax motion detectors
Indoor detectors
When properly installed and configured, indoor motion detectors ignore animals1 that are up to 50 cm in height and weigh up to 20 kg. The maximum weight is defined as an understandable orienting point, but in reality, the size of the heat spot in the infrared spectrum is of importance. Keep in mind that detectors do not see objects but instead analyze the infrared radiation of these objects.
Products
Motion detectors are less sensitive closer the ground. That’s where large pets are assumed to roam.
To assess the threat, motion detectors use the SmartDetect software algorithm developed by Ajax Systems. When motion is detected, SmartDetect analyzes the signal waveform of the infrared sensor and compares it with values specific to human motion. Because of the heat spot of an animal is small and the signals enter the lower zone of the Fresnel lens (which transmits less radiation to the sensor), the detector does not raise an alarm.
Ajax motion detectors also use the temperature compensation system. It increases the IR sensor sensitivity when the ambient temperature is close to the human body temperature (36°C) and lowers the sensitivity when the temperature contrast between the body and environment is high. Such a system helps detectors remain effective within the entire temperature range and protects them from false alarms at low temperatures. |
Outdoor detectors
Products
MotionProtect Outdoor, MotionCam Outdoor (PhOD) and MotionCam Outdoor detectors do not respond to animals with height up to 80 cm, whereas Curtain Outdoor Jeweller does not respond to animals with height up to 100 cm. To effectively ignore all outdoor-typical interference, these detectors are equipped with two infrared sensors and read signals from two areas of space. They raise an alarm only if both sensors detect motion. Curtain Outdoor Jeweller is also equipped with a K-band microwave sensor. It scans the space to prevent false alarms caused by thermal interference.
Like Ajax indoor detectors, outdoor detectors use the SmartDetect algorithm — the first software level of protection against false alarms. The algorithm analyses and compares data from each sensor. As a rule, the detector is ready to make a decision whether to ignore or raise an alarm at this stage. But if the situation is ambiguous, the spectrum analysis will be involved for frequency components of the signals of two sensors. This anti-false alarm protection system unique to volumetric security detectors was named LISA.
The DualCurtain Outdoor bidirectional outdoor curtain motion detector is equipped with two systems of two IR sensors. It has a narrow horizontal detection angle and uses a 3-step digital ELSA algorithm. When triggered, the detector sequentially compares the shapes, patterns, and time intervals of the sensor signals to filter out false alarms.
Wireless curtain-type motion detector Curtain Outdoor Jeweller with dual motion detection technology can be installed indoors and outdoors. When the device detects motion, it applies a radio-frequency scan using a K-band microwave sensor. The scan prevents false alarms. Curtain Outdoor Jeweller detects motion at a distance of up to 12 meters.
👉 Learn more about Ajax outdoor detectors
Points to consider for motion detectors to ignore animals
1. Make sure that the motion detector is installed at the optimum height.
Indoor detectors are installed at a height of 2.4 m. Curtain-type motion detectors such as MotionProtect Curtain when used in rooms with pets should be mounted upside down at a height above pet’s growth. DualCurtain Outdoor Jeweller and other outdoor volumetric detectors are installed at a height of 0.8–1.3 meters. The line of sight of the upper lens should be parallel to the ground plane. Even an imperceptible line of sight deviation at long distances will shift the field of view of the upper lens above a person or direct it to the ground. Therefore, it is important to conduct detection zones tests. Curtain Outdoor Jeweller is located at a height of 2.4 m from the ground level. For the Pet immunity feature to be effective, the detector should be installed at a height of 1 m from the ground level. The recommended height is specified relative to the optical center of the detector’s lens. |
If indoor motion detectors are installed lower than the recommended height, animals move in the hypersensitive area. If a sheepdog walks on its hind legs or even a small spaniel frolics in the chair, the detector may raise an alarm.
Outdoors, the terrain of the protected area must be taken into account. If a large dog enters the detection area of both outdoor detector lenses, pet immunity function may not be able to handle it and the system will raise an alarm.
2. Set the detector to appropriate sensitivity.
The sensitivity is selected based on the results of the detection zone test.
When protecting rooms to which animals have access, indoor detector’s settings are set to medium or low sensitivity, depending on the size of the animal. With high sensitivity, the detector does not respond to cats (up to 25 cm tall). With normal sensitivity, it does not respond to small dogs (up to 35 cm tall). With low sensitivity, it does not respond to pets up to 50 cm tall.
When properly installed and configured, Curtain Outdoor Jeweller will not respond to pets up to 1 m (100 cm) in height. We recommend installing the detector at a height of 1 m, adjusting the slider on the detector enclosure to the Pet position, and setting up the Pet immune detection mode in the app.
3. Make sure that the animal cannot approach the lens of the room detector.
The closer the moving object gets to the lens, the bigger its thermal spot becomes. If an agile dog jumps to the detector level in close proximity to the lens, an alarm will be triggered. The same goes for a cat that jumped on the closet to get close to the detector.
Note that activating the Near area detection function of DualCurtain Outdoor significantly reduces the effectiveness of pet immunity. Use this feature to protect windows and other passages that are not accessible to pets. The Near area detection mode is activated for each side on the back of the detector enclosure.
To eliminate the slightest chance of worries and unnecessary patrol dispatches due to triggering on animals, use motion detectors with visual alarm verification. When motion is detected, they take a shot or a series of 2-5 shots. Additionally, it is possible to create video scenarios using Ajax IP cameras and a video recorder. When the detector is triggered, a short video will be sent from the selected camera to the Ajax app. Both you and the security company know exactly what caused the alarm: a playful pet or a robber breaking into your house.
Products
The specified parameters differ for curtain-type motion detectors and MotionProtect G3 Fibra.
